Thiopental Other names: Sodium thiopental Sodium pentothal Thiopentone sodium Trapanal

This medicinal product is a thiobarbiturate with rapid onset for intravenous administration. Thiopental induces hypnosis and anesthesia, but not analgesia. Hypnosis is produced within 30 to 40 seconds. Recovery is within 30 minutes after adequate induction dose. Repeated injections give a prolonged anesthesia because of entry into fatty tissue.

Thiopental is a short-acting substituted barbiturate that is more lipid soluble than other groups of barbiturates. The drug reversibly depresses the activity of all excitable tissues. The CNS is particularly sensitive and normally a general anaesthesia can be achieved with thiopental without significant effects on peripheral tissues.

Thiopental acts through the CNS with particular activity in the mesencephalic reticular activating system. The barbiturates exert different effects on synaptic transmission, mostly those dependent on GABA. Autonomic ganglia of the peripheral nervous system are also depressed.

Following intravenous administration, unconsciousness occurs within 30 seconds and will be continued for 20 to 30 minutes after a single dose. Rapid uptake occurs to most vascular areas of the brain followed by redistribution into other tissues.

Thiopental is almost completely metabolized and only approximately 0.3% is excreted unchanged in the urine. Thiopental is extremely fat soluble and is largely metabolized in the liver but is slowly excreted from lipid depot and is very slowly transformed. During one hour 10-15% is metabolized, mainly in the liver. The half-life of the distribution phase after a single intravenous dose is 2-4 hours and the half-life of the elimination phase is 9-11 hours. The plasma protein binding is 80-90% at therapeutic concentration level.

There are no preclinical data.