Drug Interactions between captopril and diphenhydramine / pseudoephedrine

GENERALLY AVOID: Moderate-to-high dietary intake of potassium can cause hyperkalemia in some patients who are using angiotensin converting enzyme (ACE) inhibitors. In some cases, affected patients were using a potassium-rich salt substitute. ACE inhibitors can promote hyperkalemia through inhibition of the renin-aldosterone-angiotensin (RAA) system.

MANAGEMENT: It is recommended that patients who are taking ACE inhibitors be advised to avoid moderately high or high potassium dietary intake. Particular attention should be paid to the potassium content of salt substitutes.

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.

The use of these agents is contraindicated in patients with hereditary angioedema or a history of idiopathic angioedema. Patients with a history of angioedema unrelated to ACE inhibitors may be at increased risk of angioedema while receiving an ACE inhibitor. Patients should be advised to immediately report any signs or symptoms suggestive of angioedema (swelling of face, extremities, eyes, lips, or tongue, or difficulty swallowing or breathing) and to stop taking the medication until otherwise directed by their physician. Emergency therapy and/or measures to prevent airway obstruction are required for angioedema involving the tongue, glottis, or larynx. Treatment with ACE inhibitors should be discontinued permanently if angioedema develops in association with therapy.

ACE inhibitors may cause bone marrow suppression, rarely in uncomplicated individuals but more frequently in patients with renal impairment, especially if they also have a collagen-vascular disease such as systemic lupus erythematosus or scleroderma. Neutropenia, agranulocytosis, aplastic anemia, hemolytic anemia, eosinophilia and thrombocytopenia have been reported, mostly with captopril. Therapy with ACE inhibitors should be administered cautiously in patients with preexisting blood dyscrasias or complications that may increase the risk of bone marrow depression during ACE inhibitor therapy. Monitoring of blood counts, particularly white blood cells, should be considered.

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.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

ACE inhibitors may cause bone marrow suppression, rarely in uncomplicated individuals but more frequently in patients with renal impairment, especially if they also have a collagen-vascular disease such as systemic lupus erythematosus or scleroderma. Neutropenia, agranulocytosis, aplastic anemia, hemolytic anemia, eosinophilia and thrombocytopenia have been reported, mostly with captopril. Therapy with ACE inhibitors should be administered cautiously in patients with preexisting blood dyscrasias or complications that may increase the risk of bone marrow depression during ACE inhibitor therapy. Monitoring of blood counts, particularly white blood cells, should be considered.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

A variety of abnormal thinking and behavior changes have been reported to occur in association with the use of most anxiolytics, sedatives and hypnotics. Some of these changes include decreased inhibition, aggressiveness, agitation, and hallucinations. These drugs can cause or exacerbate mental depression and cause suicidal behavior and ideation. Therapy with these drugs should be administered cautiously in patients with a history of depression or other psychiatric disorders. Patients should be monitored for any changes in mood or behavior. It may be prudent to refrain from dispensing large quantities of medication to these patients.

In patients with hyperkalemia, especially those associated with impaired renal function or congestive heart failure, ACE inhibitors may further raise serum potassium levels. Therapy with ACE inhibitors should be administered cautiously in patients with or predisposed to hyperkalemia, and serum potassium levels should be carefully monitored. Risk factors for the development of hyperkalemia during ACE inhibitor therapy include renal insufficiency, diabetes mellitus, and the concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salt substitutes.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

Anaphylactoid reactions have been reported in patients undergoing hemodialysis with high-flux polyacrylonitrile membranes and treated concomitantly with an ACE inhibitor. The frequency and mechanism of this interaction have not been established, and it is not known whether the interaction occurs with other membrane types. Therapy with ACE inhibitors should be administered cautiously in patients requiring hemodialysis.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

In patients with hyperkalemia, especially those associated with impaired renal function or congestive heart failure, ACE inhibitors may further raise serum potassium levels. Therapy with ACE inhibitors should be administered cautiously in patients with or predisposed to hyperkalemia, and serum potassium levels should be carefully monitored. Risk factors for the development of hyperkalemia during ACE inhibitor therapy include renal insufficiency, diabetes mellitus, and the concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salt substitutes.

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.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

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.

ACE inhibitors may cause bone marrow suppression, rarely in uncomplicated individuals but more frequently in patients with renal impairment, especially if they also have a collagen-vascular disease such as systemic lupus erythematosus or scleroderma. Neutropenia, agranulocytosis, aplastic anemia, hemolytic anemia, eosinophilia and thrombocytopenia have been reported, mostly with captopril. Therapy with ACE inhibitors should be administered cautiously in patients with preexisting blood dyscrasias or complications that may increase the risk of bone marrow depression during ACE inhibitor therapy. Monitoring of blood counts, particularly white blood cells, should be considered.

In patients with hyperkalemia, especially those associated with impaired renal function or congestive heart failure, ACE inhibitors may further raise serum potassium levels. Therapy with ACE inhibitors should be administered cautiously in patients with or predisposed to hyperkalemia, and serum potassium levels should be carefully monitored. Risk factors for the development of hyperkalemia during ACE inhibitor therapy include renal insufficiency, diabetes mellitus, and the concomitant use of potassium-sparing diuretics, potassium supplements, and/or potassium-containing salt substitutes.

ACE inhibitors can cause symptomatic hypotension, most often during the initiation of therapy and in patients who are volume- and/or sodium-depleted or treated for congestive heart failure (CHF). Therapy with ACE inhibitors should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if it was recently instituted; those on dietary salt restriction; those with severe or prolonged diarrhea or vomiting; and renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with ACE inhibitors, and the patient should be hemodynamically stable. If concomitant diuretics and/or dietary sodium restriction are employed, reducing or temporarily withholding the dosing of diuretics and/or liberalizing dietary sodium intake for 2 to 3 days in advance can help minimize the risk of severe hypotension in patients who are able to tolerate such adjustments. ACE inhibitors should also be used cautiously in patients in whom excessive hypotension may have serious consequences, such as patients with coronary or cerebrovascular insufficiency. Patients at risk for excessive hypotension should initiate ACE inhibitor therapy under very close medical supervision, and followed closely for the first 2 weeks of treatment and whenever the dosage of ACE inhibitor or diuretic is increased.

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.

Oral anxiolytic, sedative, and hypnotic agents may cause respiratory depression and apnea when given in high dosages or following acute overdose. However, some patients may be susceptible at commonly used dosages, including the elderly, debilitated or severely ill patients, those receiving other CNS depressants, and those with limited ventilatory reserve, chronic pulmonary insufficiency or other respiratory disorders. Therapy with anxiolytic, sedative, and hypnotic agents should be administered cautiously in these patients. Appropriate monitoring and individualization of dosage are recommended.

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.

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.

The extended-release formulation of pseudoephedrine (Sudafed 24 Hour) contains a non-deformable material. There have been rare reports of obstructive symptoms in patients with known strictures following the ingestion of similar sustained-release products. Therapy with the extended-release formulation of pseudoephedrine should be administered cautiously in patients with preexisting severe gastrointestinal narrowing or obstruction, whether pathologic or iatrogenic.

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.

Some hypnotic drugs can have an anticholinergic effect and should be used with caution in patients with glaucoma, and trouble urinating due to retention or enlarged prostate.

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 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.

In general, anxiolytics, sedatives and hypnotics are extensively metabolized by the liver. Their plasma clearance may be decreased and their half-life prolonged in patients with impaired hepatic function. Therapy with these drugs should be administered cautiously in patients with liver disease (some are not recommended in severe liver impairment), and the dosage should be adjusted accordingly. Laboratory testing is recommended prior and during treatment.

Rarely, elevations of liver enzymes and/or serum bilirubin have occurred with the use of ACE inhibitors. Patients receiving ACE inhibitors who develop jaundice or marked elevations of hepatic enzymes should discontinue the ACE inhibitor and receive appropriate medical follow-up.

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.

Chewable products frequently may contain aspartame, which is metabolized in the gastrointestinal tract to phenylalanine. Sudafed (brand of pseudoephedrine) chewable 15 mg tablets provide the equivalent of 0.78 mg of phenylalanine per each tablet. The aspartame/phenylalanine content should be considered when this and similar products are used in patients who must restrict their intake of phenylalanine (i.e. phenylketonurics).

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.

With the exception of fosinopril, ACE inhibitors (and/or their active metabolites in some cases) are primarily eliminated by the kidney and may accumulate in patients with renal impairment. ACE inhibitors can also worsen renal function in some patients by blocking the effect of angiotensin II-mediated efferent arteriolar vasoconstriction, thereby decreasing glomerular filtration. Therapy with ACE inhibitors should be administered cautiously in patients with preexisting renal dysfunction, particularly those with renovascular disease. Patients with moderate to severe renal impairment usually require lower or less frequent doses and smaller increments in dose. In addition, a dosage reduction or discontinuation of any concomitantly administered diuretics may be helpful. Fosinopril probably does not require dosage adjustments unless hepatic function is also significantly impaired.

In patients with bilateral renal artery stenosis or renal artery stenosis in a solitary kidney, ACE inhibitors may reduce renal perfusion to a critically low level. Renal function should be monitored closely for the first few weeks of therapy.

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.

Some hypnotic drugs can have an anticholinergic effect and should be used with caution in patients with glaucoma, and trouble urinating due to retention or enlarged prostate.

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.