Carbamazepine:
- Calcium channel blockers e.g nifedipine; verapamil (may be used to treat high blood pressure); these drugs enhance the effect of carbamazepine.
- Digitoxin (for abnormal heart rhythm): reduced effect as metabolism accelerated.
- Corticosteroids reduced effect
- Diuretics ("water tablets" for fluid retention) :increased risk of hyponatraemia (low sodium)
- Danazol (hormone) enhances the effect of carbamazepine.
- Oral contraceptives: reduced contraceptive effect
- Lithium neurotoxicity may occur without raised plasma levels.
- Muscle relaxants effect may be reduced or shortened.
- Theophylline (used to treat asthma) reduced effect
- Thyroxine reduced effect
- Cimetidine (ulcer-healing) raised carbamazepine levels
- Fluoxetine (Prozac) causes raised carbamazepine levels
- Erythromycin (antibiotic) causes raised carbamazepine levels
Valproate:
- Aspirin enhances effect of valproate
- Anticoagulants (warfarin, nicoumalone) anticoagulant effect may be increased
- Antidepressants lower convulsive threshold
- Other AEDs may cause enhanced toxicity
- Antipsychotics convulsive threshold lowered
- Cimetidine increases valproate blood level
Gabapentin:
- One of the main advantages of gabapentin is the lack of drug interactions.
Lamotrigine:
- Other AEDs enhanced effects, increased sedation, may enhance toxicity
Topiramate:
Other AEDs
- Oral contraceptives reduced contraceptive effect
- Central nervous system depressants: analgesics; muscle relaxants, hypnotics (sleeping tablets)
NB. ALL AEDs INTERACT WITH ALCOHOL.
NOTE: Clonazepam is used as an AED but is from the class of drugs called benzodiazepines, which will be in another article.
Dr. S. A. Andreae-Jones MB BS
Patron of ASG
July 2000
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