Anti-epileptic drugs drug interactions

Tegretol consists of carbamazepine, which is an anti-epileptic drug. There is a clinically significant drug interaction between carbamazepine and clarithromycin (macrolide antibacterial agent) resulting in higher plasma concentrations of carbamazepine. 

It is not necessary to monitor gabapentin plasma concentrations to optimize therapy. Further, because there are no significant pharmacokinetic interactions with other commonly used anti-epileptic drugs, the addition of gabapentin does not alter the plasma levels of these drugs appreciably. 

Fig. 1. Example of a receptor structure. Some anti-epileptic drugs interact with a receptor site on a Na" " channel and enhance the activity of the inactivation gate (I) decreasing the ahihty of neurons to fire at high frequencies. (A) indicates the activation gate of this ion channel. (Reprinted by permission from McNamara JO. Emerging insights into the genesis of epilepsy. Nature 1999 399(Suppl) A15-22, 1999 Macmillan Magazines Ltd.)...

Levy RH. Cytochrome P450 isoenzymes and anti-epileptic drug interactions. Epilepsia 1995 36(Suppl 5) S8-S13. 

It is an empirical decision whether to start with duloxetine or anti-epileptics for neuropathic pain management. Vigilant follow-up and patient education on drug-drug interactions are crucial to a successful launch of duloxetine. It is prudent to start with a low dose (20-30 mg) of duloxetine and titrate cautiously to balance the risk and benefit ratio. Duloxetine doses higher than 60 mg failed to provide any additional pain relief yet caused more adverse events and withdrawals according to previous clinical studies. 

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