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Drug Interactions between carbamazepine and Viramune XR

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

carBAMazepine nevirapine

Applies to: carbamazepine and Viramune XR (nevirapine)

MONITOR: Coadministration of carbamazepine and nevirapine may result in decreased plasma concentrations of both drugs. Since both are substrates as well as inducers of CYP450 3A4, it is conceivable that each may increase metabolism of the other. However, data are limited. In four healthy, nonpregnant women, administration of a single 200 mg dose of nevirapine with 400 mg of carbamazepine resulted in a median decrease of 18.8 hours (range 15.6 to 38.0 hours) in the elimination half-life of nevirapine compared to administration alone. The decrease in nevirapine half-life led to faster undetectable nevirapine levels (median reduction in time to undetectable levels was 4 days; range 3.0 to 7.0 days), which the authors of the study suggest might reduce the risk of resistance development in pregnant women treated with single-dose nevirapine for prevention of vertical HIV transmission. However, the effect of the interaction on nevirapine during prolonged administration as part of highly active antiretroviral therapy (HAART) is unknown. In addition, the effect of nevirapine on carbamazepine pharmacokinetics has not been reported.

MANAGEMENT: Caution is advised during coadministration of carbamazepine and nevirapine. Pharmacologic effects and serum drug concentrations should be monitored more closely whenever either drug is added to or withdrawn from therapy.

References (3)
  1. (2002) "Product Information. Tegretol (carbamazepine)." Novartis Pharmaceuticals
  2. (2001) "Product Information. Viramune (nevirapine)." Boehringer-Ingelheim
  3. L'homme RF, Dijkema T, van der Ven AJ, Burger DM (2006) "Enzyme inducers reduce elimination half-life after a single dose of nevirapine in healthy women." J Acquir Immune Defic Syndr, 43, p. 193-6

Drug and food interactions

Moderate

carBAMazepine food

Applies to: carbamazepine

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of carbamazepine. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

In a small, randomized, crossover study, the administration of carbamazepine with grapefruit juice (compared to water) increased plasma drug concentrations by approximately 40%. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

MANAGEMENT: Patients receiving carbamazepine should be advised to avoid or limit consumption of alcohol. Given the drug's narrow therapeutic index, patients receiving carbamazepine therapy should preferably avoid the regular consumption of grapefruits and grapefruit juice to prevent any undue fluctuations in plasma drug levels. Patients should be advised to report signs of carbamazepine toxicity (nausea, visual disturbances, dizziness, or ataxia) to their physicians.

References (3)
  1. (2002) "Product Information. Tegretol (carbamazepine)." Novartis Pharmaceuticals
  2. Garg SK, Kumar N, Bhargava VK, Prabhakar SK (1998) "Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy." Clin Pharmacol Ther, 64, p. 286-8
  3. Bailey DG, Dresser GR, Kreeft JH, Munoz C, Freeman DJ, Bend JR (2000) "Grapefruit-felodipine interaction: Effect of unprocessed fruit and probable active ingredients." Clin Pharmacol Ther, 68, p. 468-77

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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