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TPDN 1988, Vol. 48, No. 32 Page 4
UOFNT LIBRA RE70"
Serum chloroquine concentration 11 hours after ingestion was 1.0 pgY m .1 mol/L). His
condition improved slightly during the next three weeks, and he was gradually removed from
ventilator support after one month. However, he remains unconscious with no purposeful
movement.
MMWR Editorial Note: When used for prophylaxis and treatment of malaria, chloroquine has
proven to be safe 'in the recommended dosage range (5-25 mg/kg body weight). However, a
relatively small increase in the therapeutic dose is toxic; children who have ingested two to
three times the recommended treatment dose have been fatally poisoned. Chloroquine is rapidly
absorbed from the gastrointestinal tract. Consequently, as the second case illustrates, the
interval between ingestion and cardiorespiratory collapse is frequently less than 2 hours.
A recent review of 91 cases of chloroquine poisoning in which blood concentrations were
determined revealed that no patient survived in whom blood concentrations were greater than
25 u mol/L. Since the drug is extensively tissue-bound, concentrations in the liver and kidney
are generally many times higher than those in the blood. The extensive tissue binding makes
dialysis largely ineffective in removing the drug.
The toxic effects of chloroquine are related to its depressant effect on the myocardium,
resulting in decreased cardiac output and hypotension. Like quinidine, the drug reduces the
excitability and conductivity of cardiac muscle, and at toxic concentrations profound
bradycardia with ventricular escape rhythms may occur.
Animal toxicology data and case studies of suicide attempts with chloroquine suggest that
sympathomimetic agents may decrease the hemodynamic and electrophysiologic cardiotoxic effects
of chloroquine. Diazepam has been found to decrease the mortality rate in experimental
chloroquine poisoning in rats. A recent study examined the clinical utility of immediately
administering intravenous diazepam and epinephrine in chloroquine poisoning. Ten of eleven
patients who ingested more than 5 g of chloroquine and were treated with diazepam and
epinephrine survived, as compared with 1 of 51 retrospective controls who ingested comparable
dosages.
Health-care providers should be aware of the potential interventions to prevent chloroquine
poisoning. Chloroquine prescriptions should be written for the precise amount needed for
prophylaxis for each trip to avoid accumulation of extra tablets. Any drug remaining after
prophylaxis is complete should be safely discarded. Chloroquine should be dispensed in child-
proof containers, particularly when young children are in the home.
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