Drug Interactions between chlorpheniramine / guaifenesin / phenylephrine and metformin

MetFORMIN should be taken with meals, and excessive alcohol intake (either short-term binge drinking or frequent consumption) should be avoided during treatment. Taking metFORMIN with alcohol may increase the risk of a rare but serious and potentially life-threatening condition known as lactic acidosis, which is a buildup of lactic acid in the blood that can occasionally occur during treatment with metformin-containing products. Lactic acidosis is more likely to occur if you have kidney or liver disease, acute or unstable congestive heart failure, or dehydration. You should seek immediate medical attention if you develop potential signs and symptoms of lactic acidosis such as fatigue, weakness, muscle pain, increasing drowsiness, abdominal pain or discomfort, slow or irregular heartbeat, breathing difficulty, chills, and other unusual symptoms. Alcohol may also affect blood glucose levels in patients with diabetes. Both hypoglycemia (low blood sugar) and hyperglycemia (high blood sugar) may occur, depending on how much and how often you drink. You should avoid using alcohol if your diabetes is not well controlled or if you have high triglycerides, neuropathy (nerve damage), or pancreatitis. Moderate alcohol consumption generally does not affect blood glucose levels if your diabetes is under control. However, you should limit your alcohol intake due to the risk of lactic acidosis with metformin. Avoid drinking alcohol on an empty stomach or following exercise, as it may increase the risk of hypoglycemia. Talk to your doctor or pharmacist if you have any questions or concerns about metformin.

Alcohol can increase the nervous system side effects of chlorpheniramine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with chlorpheniramine. Do not use more than the recommended dose of chlorpheniramine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Both phenylephrine and caffeine can increase blood pressure and heart rate, and combining them may enhance these effects. Talk to your doctor before using these medications, especially if you have a history of high blood pressure or heart disease. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin decreases the liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in at-risk patients. There have been reports of cases of metformin-associated lactic acidosis in patients with liver dysfunction. Metformin should generally be avoided in patients with evidence of hepatic disease.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

The use of metformin is contraindicated in patients with severe renal dysfunction (estimated GFR [eGFR] less than 30 mL/min/1.73 m2). Metformin is substantially excreted by the kidney; the risk of metformin accumulation and lactic acidosis increases with the degree of renal dysfunction. Before starting metformin, an eGFR should be obtained. Initiation of metformin is not recommended in patients with eGFR between 30 and 45 mL/min/1.73 m2. An eGFR should be obtained at least annually in all patients; in those at risk of developing renal dysfunction (e.g., older adult patients), renal function should be assessed more frequently. In patients whose eGFR falls below 45 mL/min/1.73 m2, the benefit/risk of continuing therapy should be assessed. Postmarketing cases of metformin-associated lactic acidosis primarily occurred with significant renal dysfunction; metformin plasma levels generally exceeded 5 mcg/mL.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment. Renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and contact their health care provider.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

Metformin may interfere with vitamin B12 absorption from the B12-intrinsic factor complex. A decrease to subnormal levels of previously normal serum vitamin B12 levels was reported in about 7% of patients treated with metformin during clinical trials. Such decrease may be associated with anemia but appears to be rapidly reversible with metformin discontinuation or vitamin B12 supplementation. Certain patients (those with inadequate vitamin B12 or calcium intake or absorption) appear to be predisposed to developing subnormal levels of vitamin B12; caution may be warranted when metformin is administered to these patients. It is recommended to measure vitamin B12 every 2 to 3 years and hematologic parameters annually in patients on metformin. Any abnormalities should be managed.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

It has been suggested that the anticholinergic effect of antihistamines may reduce the volume and cause thickening of bronchial secretions, resulting in obstruction of respiratory tract. Some manufacturers and clinicians recommend that therapy with antihistamines be administered cautiously in patients with asthma or chronic obstructive pulmonary disease.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

It has been suggested that the anticholinergic effect of antihistamines may reduce the volume and cause thickening of bronchial secretions, resulting in obstruction of respiratory tract. Some manufacturers and clinicians recommend that therapy with antihistamines be administered cautiously in patients with asthma or chronic obstructive pulmonary disease.

Sympathomimetic agents may cause increases in blood glucose concentrations. These effects are usually transient and slight but may be significant with dosages higher than those normally recommended. Therapy with sympathomimetic agents should be administered cautiously in patients with diabetes mellitus. Closer monitoring of blood glucose concentrations may be appropriate.

Metformin may interfere with vitamin B12 absorption from the B12-intrinsic factor complex. A decrease to subnormal levels of previously normal serum vitamin B12 levels was reported in about 7% of patients treated with metformin during clinical trials. Such decrease may be associated with anemia but appears to be rapidly reversible with metformin discontinuation or vitamin B12 supplementation. Certain patients (those with inadequate vitamin B12 or calcium intake or absorption) appear to be predisposed to developing subnormal levels of vitamin B12; caution may be warranted when metformin is administered to these patients. It is recommended to measure vitamin B12 every 2 to 3 years and hematologic parameters annually in patients on metformin. Any abnormalities should be managed.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.

Sympathomimetic agents can induce transient mydriasis via stimulation of alpha-1 adrenergic receptors. In patients with anatomically narrow angles or narrow-angle glaucoma, pupillary dilation can provoke an acute attack. In patients with other forms of glaucoma, mydriasis may occasionally increase intraocular pressure. Therapy with sympathomimetic agents should be administered cautiously in patients with or predisposed to glaucoma, particularly narrow-angle glaucoma.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

Limited pharmacokinetic data are available for the older, first-generation antihistamines. Many appear to be primarily metabolized by the liver, and both parent drugs and metabolites are excreted in the urine. Patients with renal and/or liver disease may be at greater risk for adverse effects from antihistamines due to drug and metabolite accumulation. Therapy with antihistamines should be administered cautiously in such patients. Lower initial dosages may be appropriate.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.

Limited pharmacokinetic data are available for the older, first-generation antihistamines. Many appear to be primarily metabolized by the liver, and both parent drugs and metabolites are excreted in the urine. Patients with renal and/or liver disease may be at greater risk for adverse effects from antihistamines due to drug and metabolite accumulation. Therapy with antihistamines should be administered cautiously in such patients. Lower initial dosages may be appropriate.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.