1- (aminomethyl) cyclohexane–acetic acid
The 1- (aminomethyl) cyclohexane–acetic acid class includes the drug gabapentin, which was designed to be a GABA agonist, al-though its exact mechanism of action is unknown.
Gabapentin is approved as adjunctive therapy for partial seizures in adults and in children ages 3 and older with epilepsy. It has also been used to treat pain, tremor associated with MS, bipo-lar disorder, and Parkinson’s disease as well as to prevent mi-graines.
Gabapentin is readily absorbed in the GI tract. Because of this active-transport mechanism, the drug’s bioavailability may de-crease as the dosage increases. Gabapentin isn’t metabolized; it’s excreted exclusively by the kidneys.
Gabapentin’s exact mechanism of action is unknown. The drug doesn’t appear to act at the GABA receptor, affect GABA uptake, or interfere with GABA transaminase. Instead, gabapentin appears to bind to a carrier protein and act at a unique receptor in the brain, resulting in elevated GABA levels in the brain.
Gabapentin is used as adjunctive therapy for partial and secondar-ily generalized seizures in adults and children ages 3 and older. It also seems to be effective as monotherapy although it isn’t FDA-approved for that purpose.
Like carbamazepine, gabapentin may worsen myoclonic seizures. Gabapentin doesn’t induce or inhibit hepatic enzymes, so it causes very few drug interactions and doesn’t affect the metabo-lism of other anticonvulsants. Antacids and cimetidine may affectgabapentin concentration.
Patients with renal impairment (creatinine clearance less than 60 ml/minute) require a dosage reduction. (See Adverse reactionsto gabapentin.)