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Drug Interactions between Felbatol and Tegretol

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

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Interactions between your drugs

Moderate

carBAMazepine felbamate

Applies to: Tegretol (carbamazepine) and Felbatol (felbamate)

ADJUST DOSE: Felbamate may increase the plasma clearance of carbamazepine but decrease the plasma clearance of carbamazepine epoxide (the metabolite that is one of the principal causes of carbamazepine side effects). Increased plasma carbamazepine epoxide levels may result. Additionally, carbamazepine may cause a 50% increase in the plasma clearance of felbamate.

MANAGEMENT: When combination therapy is started, felbamate should be initiated at 1200 mg per day in 3 to 4 divided doses while reducing the carbamazepine dose by 20% to 30%. In general, the felbamate dose may be titrated more quickly than when felbamate is given as monotherapy. Close observation for clinical and laboratory evidence of altered effects is indicated. Patients should be advised to report worsening of seizure control or signs of carbamazepine toxicity (nausea, visual disturbances, dizziness, or ataxia) to their physician.

References

  1. Wagner ML, Remmel RP, Graves NM, Leppik IE (1993) "Effect of felbamate on carbamazepine and its major metabolites." Clin Pharmacol Ther, 53, p. 536-43
  2. Wagner ML, Graves NM, Marienau K, Holmes GB, Remmel RP, Leppik IE (1991) "Discontinuation of phenytoin and carbamazepine in patients receiving felbamate." Epilepsia, 32, p. 398-406
  3. Albani F, Theodore WH, Washington P, Devinsky O, Bromfield E, Porter RJ, Nice FJ (1991) "Effect of felbamate on plasma levels of carbamazepine and its metabolites." Epilepsia, 32, p. 130-2
  4. Graves NM, Holmes GB, Fuerst RH, Leppik IE (1989) "Effect of felbamate on phenytoin and carbamazepine serum concentrations." Epilepsia, 30, p. 225-9
  5. Fuerst RH, Graves NM, Leppik IE, Brundage RC, Holmes GB, Remmel RP (1988) "Felbamate increases phenytoin but decreases carbamazepine concentrations." Epilepsia, 29, p. 488-91
  6. (2001) "Product Information. Felbatol (felbamate)." Wallace Laboratories
View all 6 references

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Drug and food interactions

Moderate

carBAMazepine food

Applies to: Tegretol (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. (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

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Moderate

felbamate food

Applies to: Felbatol (felbamate)

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

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

References

  1. Warrington SJ, Ankier SI, Turner P (1986) "Evaluation of possible interactions between ethanol and trazodone or amitriptyline." Neuropsychobiology, 15, p. 31-7
  2. Gilman AG, eds., Nies AS, Rall TW, Taylor P (1990) "Goodman and Gilman's the Pharmacological Basis of Therapeutics." New York, NY: Pergamon Press Inc.
  3. (2012) "Product Information. Fycompa (perampanel)." Eisai Inc
  4. (2015) "Product Information. Rexulti (brexpiprazole)." Otsuka American Pharmaceuticals Inc
View all 4 references

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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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