Drug Interactions between carbamazepine and Welchol
This report displays the potential drug interactions for the following 2 drugs:
- carbamazepine
- Welchol (colesevelam)
Interactions between your drugs
carBAMazepine colesevelam
Applies to: carbamazepine and Welchol (colesevelam)
ADJUST DOSING INTERVAL: Colesevelam may decrease the gastrointestinal absorption of coadministered drugs. Approximately 20% to 40% reductions in systemic exposure (AUC) and 10% to 45% reductions in peak plasma concentration (Cmax) have been reported for cyclosporine, ethinyl estradiol, glimepiride, glyburide, levothyroxine, olmesartan, and sustained-release verapamil during coadministration with colesevelam. Significant pharmacokinetic changes were not observed when the drugs were administered 4 hours prior to colesevelam. During postmarketing use of colesevelam, there have been rare reports of suspected interaction with phenytoin, as evidenced by increased seizure activity or decreased phenytoin levels. Elevated thyroid-stimulating hormone (TSH) levels have also been observed in patients receiving thyroid hormone replacement therapy.
MANAGEMENT: In general, drugs with a narrow therapeutic index as well as those that have been shown to interact with colesevelam should be administered at least 4 hours before the colesevelam dose. Clinical and laboratory monitoring of drug levels and effects should be considered.
References
- (2001) "Product Information. Welchol (colesevelam)." Daiichi Sankyo, Inc.
- Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
Drug and food interactions
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
- (2002) "Product Information. Tegretol (carbamazepine)." Novartis Pharmaceuticals
- 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
- 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.
See also
Drug Interaction Classification
Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
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. | |
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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