Letter: Action of cysteamine in paracetamol poisoning

Paracetamol

Paracetamol is an analgesic and antipyretic agent which was first marketed for use as a drug in the U.K. in 1956. It has since become popular with the medical profession and the general public as an alternative to aspirin.

Late treatment of paracetamol poisoning with mercaptamine

Forty patients who had taken overdoses of paracetamol were treated with mercaptamine. Twenty-three patients given mercaptamine within 10 hours of poisoning had normal liver function tests at follow-up, and one could not be traced. In 16 patients mecraptamine was begun more than 10 hours after ingestion of paracetamol ("late" mercaptamine). Eight of these patients developed severe liver damage, which in six was moderate or severe before mercaptamine administration. Acute renal failure occurred in two patients; in one other renal function was temporarily severely impaired. At follow-up two patients were not available, and one admitted moribund had died soon after admission. The remaining 13 all had normal liver function tests. It is concluded that late mercaptamine is not dangerous and may prevent further liver damage.

A theoretical approach to the management of paracetamol overdosage

Possible ways of treating paracetamol hepatotoxicity are briefly reviewed. This toxicity appears to be due to an oxidation metabolite which is normally detoxified by conjugation with glutathione, but when in excess, as in paracetamol overdosage, binds covalently to hepatic proteins to cause liver necrosis. Depletion of hepatic glutathione may also lead to other contributory disorders of cellular metabolism. Physical methods of preventing this would appear to be of little value, and treatments are being developed which aim to lessen the production of the toxic metabolite, antagonize its attachment to hepatic tissue or to combat this toxicity via basic cellular mechanisms. At this moment the most effective substances appear to be glutathione precursors and other compounds which interfere with oxidation of paracetamol.