A convulsant is a drug which induces or epileptic seizures, the opposite of an anticonvulsant. These drugs generally act as at low doses, but are not used for this purpose due to poor therapeutic indices. Most convulsants are antagonists (or ) at either the GABA-A receptor or/and (e.g the pesticide fipronil), or ionotropic glutamate receptor (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.
Uses
Some convulsants such as
pentetrazol and
flurothyl were previously used in shock therapy in psychiatric medicine, as an alternative to electroconvulsive therapy.
Others such as
strychnine and tetramethylenedisulfotetramine are used as
.
Bemegride and
flumazenil are used to treat drug
(of
barbiturates and
respectively), but may cause convulsions if the dose is too high.
Convulsants are also widely used in scientific research, for instance in the testing of new anticonvulsant drugs. Convulsions are induced in captive animals, then high doses of anticonvulsant drugs are administered.
For example,
kainic acid can lead to status epilepticus in animals as it is a cyclic analog of
l-glutamate and an agonist for
in the brain which makes it a potent neurotoxin and excitant.
Examples
GABAA receptor antagonists, inverse agonists or negative allosteric modulators
GABA
A receptor antagonists are drugs that bind to
GABAA receptor but do not activate them and inhibit the action of GABA. Thus it blocks both the endogenous and exogenous actions of GABA
A receptor agonists.
GABA synthesis inhibitors
GABA synthesis inhibitors are drugs that inhibit the action of
GABA.
Glycine receptor antagonists
Glycine receptor antagonists are drugs which inactivates the glycine receptors.
Ionotropic glutamate receptor agonists
Ionotropic glutamate receptor agonists are drugs that activate the ionotropic glutamate receptors in the brain.
Acetylcholine receptor agonists
Acetylcholine receptor agonists are drugs that activate the acetylcholine receptors.
Advantages
Camphor injections for psychiatric treatment were inefficient and were replaced by pentylenetetrazol. Seizures induced by chemicals like flurothyl were clinically effective as electric convulsions with lesser side effects on memory retention. Therefore, considering flurothyl induced seizures in modern anesthesia facilities is encouraged to relieve medication treatment resistant patients with psychiatric illnesses like mood disorders and catatonia.
Risks/Complications
Convulsants like pentylenetetrazol and
flurothyl were effective in psychiatric treatment but difficult to administer. Flurothyl was not widely being used due to the persistence of the ethereal aroma and fears in the professional staff that they might seize.
History
In 1934, camphor-induced and pentylenetetrazol-induced brain seizures were first used to relieve psychiatric illnesses. But camphor was found ineffective. In 1957, inhalant anesthetic flurothyl was tested and found to be clinically effective in the induction of seizures, even though certain risks persisted.
