Adding a new prescription, stopping a prescription, or starting or stopping the use of some OTC products may require adjustments to the dosage of Tegretol-XR (extended-release carbamazepine) or the other drug.

Effects of carbamazepine on other drugs
Because carbamazepine accelerates hepatic metabolism, it will increase the clearance of:

• oral contraceptives
• valproate
• phenytoin
• phenobarbital
• primidone
• clonazepam
• topiramate
• ethosuximide
• corticosteroids
• warfarin
• antipsychotics
• cyclosporine

Effects of other drugs on carbamazepine
Drugs that will increase the serum concentration of carbamazepine by inhibiting its hepatic metabolism include:

• valproate
• cimetidine
• dextropropoxyphene
• diltiazem
• erythromycin
• isoniazid
• verapamil
• viloxazine
• fluoxetine
• fluconazole, ketoconazole, metronidazole, nefazodone

Grapefruit juice has a similar effect.

Taking carbamazepine simultaneously with lamotrigine may increase the likelihood of neurotoxic side effects. Staggering the doses of carbamazepine and lamotrigine by 1 to 2 hours may lessen this effect, even with Tegretol-XR.

On the other hand, drugs that accelerate hepatic metabolism will lower serum concentrations of carbamazepine. These include:

• phenytoin
• oxcarbazepine
• phenobarbital
• primidone
• felbamate

AED Interaction Sheets:
Seizure drugs are often affected by drug-drug interactions. Print these informative sheets for practical help.

• Interaction sheet for carbamazepine (Tegretol, Tegretol XR, Carbatrol)