Most of the drugs are metabolized by the liver, The Cytochrome P450 enzymes are predominantly responsible for metabolizing the drugs. Some drugs have the potential to induce or inhibit this Cytochrome P450 pathway. Those drugs which induce this cytochrome p450 pathway cause decrease in the efficacy of other drugs which are metabolized by this pathway, because, due to increase in the number of p450 enzymes the drug is quickly metabolized without achieving its pharmacological goal. On the other hand, if cytochrome p450 pathway is inhibited, the concentration of drug which uses this pathway for its metabolism, will increase, because the cytochrome enzymes are inhibited by the other drug and are no longer available to metabolize this drug.
Most of the antiepileptic drugs affect the cytochrome p450 pathway, so are not safe if given in combination with other drugs which use cytochrome p450 pathway for their metabolism. The anti-epileptic drugs that don’t affect the cytochrome p450 liver enzyme pathway are;
- Gabapentin
- Levetiracetam
- Vigabatrin
Only these drugs do not affect the cytochrome p450 enzyme pathway, so are the safest if used in combination with other drugs, if there is an indication.
In general if you a patient is taking multiple drugs for multiple co-morbidities, then it is safe to choose one of the above drugs, if prevention of seizure is required.
