06.03 Preventing Absorption

The standard treatment of poisoning used to be to make the patient sick (emesis). However, emesis with syrup of ipecac is now rarely used. When used soon after the intake of certain drugs, emesis can be useful, but it is often difficult to ascertain when the poison was taken and hence how much poison is still in the stomach.

In several situations, emesis can do more harm than good. For instance, if the patient becomes comatose, emesis can cause aspiration of the gastric contents. Similarly, if the patient is delirious, aspiration can occur. Aspiration is when the contents of the stomach are delivered to the lung, and can be fatal. Also, if the patient has ingested a central stimulant, and is delirious or has hallucinations, the further stimulation associated with vomiting may precipitate convulsions.

Syrup of ipecac is derived from a plant source, and is available on prescription or OTC (Over-The-Counter). It has both a local irritant effect on enteric tract and stimulates the chemoreceptor trigger zone (CTZ) or emetic centre in the area postrema of the medulla to induce emesis. Syrup of ipecac is indicated when it can be administered to conscious, alert patients within 60 minutes of poisoning, and produces vomiting in 15-30 minutes.

In addition to emesis, there are two other ways to limit drug absorption. The first is gastric lavage, which is restricted to patients who have taken a life-threatening amount of drug within the last 60 min. For gastric lavage, a tube and large syringe are required. The contents of the stomach are aspirated (sucked up), and then the stomach is lavaged (washed) with saline.

The second alternative to emesis is activated charcoal. Activated charcoal adsorbs many drugs preventing their absorption and toxicity. Activated charcoal, does not need to be removed artificially, nature can takes its course. The use of activated charcoal has increased recently. It is indicated for life-threatening amounts of the anti-epileptic drug carbamazepine.