Anticonvulsants in Psychiatry: Their Similarities Are Different; Part 1-Mechanism of Action

Article excerpt

Issue All anticonvulsants reduce seizures, but not all anticonvulsants have identical pharmacologic mechanisms of action (1-8)

Actions Learn the different mechanisms of action of anticonvulsants

Benefits Understanding mechanism of action of anticonvulsants (1-8) should help a prescriber match the best drug action to the specific psychiatric disorder of a given patient


Although all anticonvulsants share the common property of reducing seizures, they do so in different ways. Because of their divergent mechanisms of action, each anticonvulsant may have a unique therapeutic profile outside of epilepsy. In fact, clinical data already suggest that many anticonvulsants are effective in bipolar disorder, schizophrenia, anxiety, and chronic pain, but that not all anticonvulsants are effective in the same disorders. It is therefore important to understand the mechanism of action of each agent in order to select an anticonvulsant that can effectively treat the presenting symptoms of a given patient.

Anticonvulsants and Voltage-Sensitive Ion Channels

Neurotransmitter release from presynaptic nerve terminals is linked to both voltage-sensitive sodium channels (VSSC) and voltage-sensitive calcium channels (VSCC) (figure). Several anticonvulsants bind to VSSCs, some acting directly at a specific site within the channel itself (lamotrigine, carbamazepine, oxcarbazepine, and possibly zonisamide), and others acting at sites not yet well-characterized (valproate, topiramate), (1,5,6) Other anticonvulsants (gabapentin, pregabalin) bind to the alpha 2 delta subunit of VSCCs. (1,3,4,7)

Anticonvulsants and Other Mechanisms of Action

Benzodiazepines bind to gamma-aminobutyric acid (GABA) A receptors to enhance the inhibitory effects of GABA. (1) Tiagabine blocks the GABA reuptake pump, (1,2) while vigabatrin irreversibly blocks GABA-T, the enzyme that breaks down GABA. …