Convulsant

A convulsant is a drug which induces convulsions or epileptic seizures, the opposite of an anticonvulsant. These drugs generally act as stimulants at low doses, but are not used for this purpose due to poor therapeutic indices. Most convulsants are antagonists (or inverse agonists) at either the GABA_A or/and glycine receptors (e.g the pesticide fipronil), or ionotropic glutamate receptor agonists (e.g the marine toxin domoic acid). Many other drugs may cause convulsions as a side effect at high doses (e.g. bupropion, tramadol, pethidine, dextropropoxyphene, clomipramine) but only drugs whose primary action is to cause convulsions are known as convulsants. Nerve agents such as sarin, which were developed as chemical weapons, produce convulsions as a major part of their toxidrome, but also produce a number of other effects in the body and are usually classified separately. Dieldrin which was developed as an insecticide blocks chloride influx into the neurons causing hyperexcitability of the CNS and convulsions. The Irwin observation test and other studies that record clinical signs are used to test the potential for a drug to induce convulsions. Camphor, and other terpenes given to children with colds can act as convulsants (sympathomimetics, piperazine derivatives, theophylline, antihistamines, etc.) in children who have had febrile seizures.