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Drug Interactions between carbamazepine and methazolamide

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

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Interactions between your drugs

Moderate

carBAMazepine methazolAMIDE

Applies to: carbamazepine and methazolamide

MONITOR: Coadministration with a carbonic anhydrase inhibitor may increase the serum concentration and the risk of toxicity of carbamazepine. The mechanism of this interaction has not been delineated. In one report, three pediatric patients receiving the highest tolerable dose of carbamazepine without adverse effects experienced a 25% to 50% increase in their serum carbamazepine levels following the addition of acetazolamide 250 mg to 750 mg daily. In another report involving 54 pediatric patients with epilepsy, seizure control improved following the addition of acetazolamide 10 mg/kg daily and serum carbamazepine levels increased by 1 to 6 mg/L in 60% of 33 patients sampled. In those patients who developed carbamazepine toxicity, symptoms developed within 1 to 10 days of starting acetazolamide.

MANAGEMENT: Clinical monitoring of carbamazepine serum concentrations is recommended and the dosage should be adjusted accordingly. Patients should be advised to report possible signs of carbamazepine toxicity, such as headache, nausea, dizziness, slurred speech, nystagmus, visual disturbances, tremors, and ataxia, to their caregiver.

References (4)
  1. (2002) "Product Information. Tegretol (carbamazepine)." Novartis Pharmaceuticals
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  3. Cerner Multum, Inc. "Australian Product Information."
  4. Forsythe WI, Owens JR, Toothill C (1981) "Effectiveness of acetazolamide in the treatment of carbamazepine-resistant epilepsy in children." Dev Med Child Neurol, 23, p. 761-9

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

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