Drug Interactions between mefloquine and Quadrapax

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Mefloquine may increase the risk of seizures and decrease the effectiveness of anticonvulsant drugs in patients with epilepsy. The use of mefloquine alone and in combination with other related antimalarial agents (e.g., quinine, quinidine, chloroquine) has been associated with convulsions in some patients. Coadministration of mefloquine with certain anticonvulsant medications may also result in reduced seizure control by lowering the plasma levels of the anticonvulsant. In one case report, a patient with a seizure disorder previously well controlled on valproic acid and carbamazepine experienced several seizure episodes after taking mefloquine (250 mg weekly) for malaria prophylaxis. A subsequent kinetics study performed on the patient revealed a significant reduction in sodium valproate half-life (5.65 hours vs. reported normal of 8 to 20 hours) and no change in carbamazepine half-life. The author suggested that mefloquine be administered to epileptic patients with caution, particularly if being treated with sodium valproate. Additional clinical data with other antiepileptics are unavailable.

MANAGEMENT: According to the product labeling, mefloquine may precipitate convulsions in patients with a history of seizure disorder and should not be used for malaria prophylaxis in such patients. If mefloquine administration is required for curative treatment of malaria, anticonvulsant blood levels should be closely monitored and the anticonvulsant dosage adjusted accordingly as needed. Patients should be advised to notify their physician if they experience a loss of seizure control.

MONITOR CLOSELY: Coadministration with potent inducers of CYP450 3A4 may significantly decrease the plasma concentrations of mefloquine, which is primarily metabolized by the isoenzyme. In seven healthy, nonsmoking male volunteers, administration of a single 500 mg oral dose of mefloquine on day 7 of treatment with the potent CYP450 3A4 inducer rifampin (600 mg orally once daily on days 1 through 7, followed by 600 mg twice weekly on days 8 through 56) decreased mean mefloquine peak plasma concentration (Cmax) and systemic exposure (AUC) by 19% and 68%, respectively, compared to mefloquine administered alone. The mean elimination half-life of mefloquine was also decreased by 63% (from 305 to 113 hours) in the presence of rifampin, while mean apparent oral clearance increased by 281%.

MANAGEMENT: The possibility of diminished antimalarial efficacy should be considered when mefloquine is used in combination with potent CYP450 3A4 inducers. Alternative agents with minimal or less enzyme induction potential are recommended when possible to avoid the risk of therapeutic failure, particularly in the treatment of acute malaria infections.

Using atropine together with hyoscyamine may increase side effects such as drowsiness, blurred vision, dry mouth, heat intolerance, flushing, decreased sweating, difficulty urinating, abdominal cramping, constipation, irregular heartbeat, confusion, and memory problems. Side effects may be more likely to occur in the elderly or those with a debilitating condition. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. 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.

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Using atropine together with scopolamine may increase side effects such as drowsiness, blurred vision, dry mouth, heat intolerance, flushing, decreased sweating, difficulty urinating, abdominal cramping, constipation, irregular heartbeat, confusion, and memory problems. Side effects may be more likely to occur in the elderly or those with a debilitating condition. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. 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.

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Using PHENobarbital together with scopolamine may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. 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.

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Using hyoscyamine together with scopolamine may increase side effects such as drowsiness, blurred vision, dry mouth, heat intolerance, flushing, decreased sweating, difficulty urinating, abdominal cramping, constipation, irregular heartbeat, confusion, and memory problems. Side effects may be more likely to occur in the elderly or those with a debilitating condition. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. 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.

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