Pharmacology Notes

There is limited evidence for the use of activated charcoal. The current international consensus is for its use only in significant poisoning within one hour of the estimated time of ingestion and for slow-release preparations at any time. In this situation, use:

However, there are good theoretical reasons, and some evidence, for the use of charcoal later than one hour after ingestion. This is based on some recent studies on the effect of charcoal on clearance for particular drugs, and the fact that most studies of activated charcoal have excluded patients who have ingested severely toxic agents. Therefore the recommendation for the use of activated charcoal and the timing of its use will vary for some agents. This is described under each individual drug or toxin.

The use of activated charcoal containing sorbitol or other cathartics is no longer recommended.

Whole bowel irrigation (WBI) should be considered within the first few hours for ingestions of metals or slow-release preparations. Specific examples include patients who have ingested significant iron overdose (greater than 60 mg/kg), lead, arsenic trioxide causing symptoms, lithium, slow-release potassium chloride (greater than 2.5 mmol/kg), slow-release verapamil or life-threatening doses of of slow-release diltiazem. Another group in whom whole bowel irrigation may be considered is body packers [Note 1].

Although there are good theoretical reasons for using whole bowel irrigation in these situations, there is little evidence to support its use. It is essential to carefully balance the possible benefits against the significant risk of aspiration and practical difficulties of administering whole bowel irrigation. Particular issues are the potential for vomiting and profuse diarrhoea to interfere with timely retrieval and life-saving interventions. Whole bowel irrigation is contraindicated in patients with gastrointestinal ileus. Development of ileus must, therefore, be carefully monitored by listening for bowel sounds, particularly in intubated patients and patients ingesting anticholinergic drugs. It is reasonable to discuss the use of whole bowel irrigation for individual patients with a clinical toxicologist. Use:

There is limited evidence for multiple-dose activated charcoal but it is recommended for some agents—carbamazepine, quinine, theophylline, phenobarbitone, oleander.

Patients who have been doused in, or who have ingested with associated spillage of, hazardous materials should have all of their clothes removed and then be washed in a shower with soapy water. Once this has been done there is then no risk of secondary contamination or poisoning by toxic agents in persons looking after these patients. An Australian consensus statement on nosocomial risk in organophosphate poisoning has been published. [Note 3]

Gastric lavage is no longer recommended, except in rare circumstances where a single aspiration of the stomach contents may be attempted early in potentially life-threatening poisoning and only if the airway is protected. A safe option is to simply suction out the contents of the stomach if the patient has been intubated but instillation of fluid in the stomach is not recommended.

Inducing emesis by any means is not recommended due to the risks of aspiration. Syrup of Ipecac is not recommended at all and ipecacuanha is no longer available in this formulation in Australia. This is due to lack of effectiveness and the risks of aspiration if the patient becomes sedated and then begins to vomit.

Ocular decontamination requires copious irrigation with either water or normal saline. For substances that are irritant and minimally corrosive then irrigation for 15 to 20 minutes is usually sufficient. For corrosive agents irrigation should continue longer, see Eye trauma: chemical burns.