ABSTRACT
Drug interactions are a ubiquitous phenomenon. The potential for interactions exists at many levels whenever two or more agents are used in combination. Because combination therapy has gained widespread acceptance it is easy to forget the complications stemming from the use of multiple drugs simultaneously. The activity of the antiepileptic drugs in the maximal electroshock seizure model in combination in rats was found to be additive, with no synergistic or pharmacodynamic interaction. Antiepileptic medications may interact with each other when used in combination therapy, and other drugs, prescription or “over the counter”, may also participate in these interactions. Pharmacokinetic interactions are ubiquitous. These may occur at any of the three arenas of pharmacokinetic interest: absorption, distribution, and elimination. Some antiepileptic drugs are very insoluble in aqueous solutions, and sensitive to any effects which alter solubility, dissolution, or gastrointestinal motility. Pharmacodynamic interaction between carbamazepine and phenytoin and possibly phenobarbital was postulated to occur from clinical studies.
