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Drug Interactions between carbamazepine and topiramate

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

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Interactions between your drugs

Moderate

carBAMazepine topiramate

Applies to: carbamazepine and topiramate

ADJUST DOSE: Carbamazepine, when coadministered with topiramate may lead to a 40% decrease in the plasma concentration of topiramate. The mechanism appears to be hepatic enzyme induction with subsequent increased metabolism of topiramate. In contrast, some evidence suggests that toxicity may occur when topiramate is added to the maximum tolerated doses of carbamazepine.

MANAGEMENT: If dosages of topiramate have been adjusted upward, reduction or withdrawal of carbamazepine during adjunctive therapy may require a downward dose adjustment of topiramate. In general, no adjustment in carbamazepine dosage is required when topiramate adjunctive therapy is started; however, if toxicity develops when topiramate is added to the maximum tolerated dose of carbamazepine, a reduction in the carbamazepine dose should be considered. Patients should be monitored for altered efficacy and safety and should be advised to notify their physician if seizure control worsens or adverse effects occur.

References

  1. Sachdeo RC, Sachdeo SK, Walker SA, Kramer LD, Nayak RK, Doose DR "Steady-state pharmacokinetics of topiramate and carbamazepine in patients with epilepsy during monotherapy and concomitant therapy." Epilepsia 37 (1996): 774-80
  2. Bourgeois BF "Drug interaction profile of topiramate." Epilepsia 37(suppl 2 (1996): s14-7
  3. "Product Information. Topamax (topiramate)." Ortho McNeil Pharmaceutical PROD (2001):
  4. Mack CJ, Kuc S, Mulcrone SA, Pilley A, Grunewald RA "Interaction of topiramate with carbamazepine: two case reports and a review of clinical experience." Seizure 11 (2002): 464-7
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  6. Cerner Multum, Inc. "Australian Product Information." O 0
View all 6 references

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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

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

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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.

See also

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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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