Topiramate drug interactions

Topiramate
TOPIRAMATE® FDA Package Insert
Indications and Usage
Dosage and Administration
Dosage Forms and Strengths
Contraindications
Warnings and Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Overdosage
Description
Clinical Pharmacology
Nonclinical Toxicology
Clinical Studies
How Supplied/Storage and Handling
Patient Counseling Information
Labels and Packages
Clinical Trials on Topiramate
ClinicalTrials.gov

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Pratik Bahekar, MBBS [2]

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Drug Interactions

• As topiramate inhibits carbonic anhydrase, the concomitant use of other inhibitors of carbonic anhydrase (e.g. acetazolamide) may lead to an increased risk of renal stones.
• Enzyme inductors (e.g. carbamazepine) : The elimination of topiramate may be increased, possibly requiring dose escalations of topiramate.
• Phenytoin : Topiramate may increase the plasma-levels of phenytoin.
• Topiramate itself is a weak inhibitor of CYP 2C19 and induces CYP 3A4. Under topiramate a decrease of plasma-levels of estrogens (e.g. 'the pill') and digoxin have been noted.
• Alcohol may cause increased sedation or drowsiness, and increase the risk of having a seizure.
• As listed in the 06/29/2005 label posted at the Drugs@FDA website page 14,'conditions or therapies that predispose to acidosis may be additive to the bicarbonate lowering effects of Topiramate'. Absent from this label is any direct discussion of narcotic (drugs known to promote respiratory acidosis) interactions. This discussion on page 14 is under the topic of Metabolic Acidosis, and is not repeated under the topic of interactions.

• Oral contraceptives: Decreased contraceptive efficacy and increased breakthrough bleeding should be considered, especially at doses greater than 200 mg/day .
• Metformin is contraindicated with metabolic acidosis, an effect of topiramate.
• Lithium levels should be monitored when coadministered with high-dose topiramate.
• Other carbonic anhydrase inhibitors: Monitor the patient for the appearance or worsening of metabolic acidosis.