Pharmacokinetics
Onset time: 30 seconds         Offset time: 5-10 minutes
Metabolism: In the liver to the active oxybarbiturate derivative pentobarbital and two other inactive metabolites.

Pharmacodynamics
CNS: Hypnosis; antiepileptic; antanalgesic.

Common side-effects
CVS: Direct myocardial depression with hypotension and reduction in cardiac output. Use with caution in the hypovolaemic patient.
RS: Dose-dependent reduction in minute ventilation, commonly with a short period of apnoea.

Problems with use
Extremely painful and limb-threatening if given intra-arterially. Urgent treatment includes: Saline dilution, papaverine 40 mg to dilate the artery and sympathetic blockade to improve blood flow.
Hypersensitivity reactions: Approximately 1 in 15 000.

Absolute contraindication to use
Porphyria.