Drug Interactions between MLK F2 and phenazopyridine

GENERALLY AVOID: Additive toxicities may occur when bupivacaine is coadministered with other local anesthetics. The potential for increased risk of systemic toxicities such as methemoglobinemia and central nervous system and cardiovascular adverse reactions should be recognized.

MANAGEMENT: Additional use of local anesthetics should generally be avoided within 96 hours following administration of bupivacaine. If coadministration cannot be avoided, overall local anesthetic exposure through 72 hours must be considered in addition to monitoring for the development of methemoglobinemia as well as central nervous system and cardiovascular adverse reactions. Signs and symptoms of methemoglobinemia may be delayed some hours after drug exposure. Patients or their caregivers should be advised to seek medical attention if they notice signs and symptoms of methemoglobinemia such as slate-grey cyanosis in buccal mucous membranes, lips, and nail beds; nausea; headache; dizziness; lightheadedness; lethargy; fatigue; dyspnea; tachypnea; tachycardia; palpitation; anxiety; and confusion. In severe cases, patients may progress to central nervous system depression, stupor, seizures, acidosis, cardiac arrhythmias, syncope, shock, coma, and death. Early warning signs of central nervous system toxicity may include restlessness, anxiety, incoherent speech, dizziness, lightheadedness, numbness and tingling of the mouth and lips, metallic taste, tinnitus, blurred vision, tremors, twitching, depression, and drowsiness. Cardiovascular toxicity may include atrioventricular block, ventricular arrhythmias, cardiac arrest, and decreased cardiac output and arterial blood pressure due to depressed cardiac conductivity, excitability, and myocardial contractility. Patients should have cardiovascular and respiratory vital signs and state of consciousness constantly monitored while under treatment.

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MONITOR: Coadministration of local anesthetics with other oxidizing agents that can also induce methemoglobinemia such as antimalarials (e.g., chloroquine, quinine), nitrates and nitrites, sulfonamides, aminosalicylic acid, dimethyl sulfoxide (DMSO), metoclopramide, nitrofurantoin, phenazopyridine, phenobarbital, and phenytoin may increase the risk. Additional risk factors include very young age (e.g., infants less than 6 months), cardiac or pulmonary disease, genetic predisposition, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Data surrounding the incidence of methemoglobinemia are agent-specific and, in many instances, have primarily been reported in case reports and/or in overdose situations.

MANAGEMENT: Monitoring for signs and symptoms of methemoglobinemia is recommended if local anesthetics must be used with other methemoglobin-inducing agents. Signs and symptoms of methemoglobinemia may occur immediately or hours after drug exposure. Patients or their caregivers should be advised to seek medical attention if they notice signs and symptoms of methemoglobinemia (e.g., cyanotic skin discoloration, abnormal blood coloration, nausea, headache, dizziness, lightheadedness, lethargy, fatigue, dyspnea, tachypnea, tachycardia, palpitation, anxiety, and confusion). In severe cases, patients may progress to central nervous system depression, stupor, seizures, acidosis, cardiac arrhythmias, syncope, shock, coma, and death. Methemoglobinemia should be considered if central cyanosis is unresponsive to oxygen. Calculated oxygen saturation and pulse oximetry are generally not accurate in the setting of methemoglobinemia. The diagnosis can be confirmed by an elevated methemoglobin level of at least 10% using co-oximetry. Methemoglobin concentrations greater than 10% of total hemoglobin will typically cause cyanosis, and levels over 70% are frequently fatal. However, symptom severity is not always related to methemoglobin levels. Experts suggest that treatment of methemoglobinemia varies from supplemental oxygen and symptom support to the administration of methylene blue, depending on severity of symptoms and/or the presence of G6PD deficiency. Institutional guidelines and/or individual product labeling should be consulted for further guidance.

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MONITOR: Coadministration of local anesthetics with other oxidizing agents that can also induce methemoglobinemia such as antimalarials (e.g., chloroquine, quinine), nitrates and nitrites, sulfonamides, aminosalicylic acid, dimethyl sulfoxide (DMSO), metoclopramide, nitrofurantoin, phenazopyridine, phenobarbital, and phenytoin may increase the risk. Additional risk factors include very young age (e.g., infants less than 6 months), cardiac or pulmonary disease, genetic predisposition, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Data surrounding the incidence of methemoglobinemia are agent-specific and, in many instances, have primarily been reported in case reports and/or in overdose situations.

MANAGEMENT: Monitoring for signs and symptoms of methemoglobinemia is recommended if local anesthetics must be used with other methemoglobin-inducing agents. Signs and symptoms of methemoglobinemia may occur immediately or hours after drug exposure. Patients or their caregivers should be advised to seek medical attention if they notice signs and symptoms of methemoglobinemia (e.g., cyanotic skin discoloration, abnormal blood coloration, nausea, headache, dizziness, lightheadedness, lethargy, fatigue, dyspnea, tachypnea, tachycardia, palpitation, anxiety, and confusion). In severe cases, patients may progress to central nervous system depression, stupor, seizures, acidosis, cardiac arrhythmias, syncope, shock, coma, and death. Methemoglobinemia should be considered if central cyanosis is unresponsive to oxygen. Calculated oxygen saturation and pulse oximetry are generally not accurate in the setting of methemoglobinemia. The diagnosis can be confirmed by an elevated methemoglobin level of at least 10% using co-oximetry. Methemoglobin concentrations greater than 10% of total hemoglobin will typically cause cyanosis, and levels over 70% are frequently fatal. However, symptom severity is not always related to methemoglobin levels. Experts suggest that treatment of methemoglobinemia varies from supplemental oxygen and symptom support to the administration of methylene blue, depending on severity of symptoms and/or the presence of G6PD deficiency. Institutional guidelines and/or individual product labeling should be consulted for further guidance.

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