Chloroquine

Introduction

Chloroquine is a medication used to treat malaria as well as certain rheumatological conditions; it has a 4-amino-quinoline chemical structure similar to that of quinidine. Hydroxy chloroquine is another structurally similar agent that is often used therapeutically instead of chloroquine as it is believed to be modestly less toxic. The clinical profile of both drugs in overdose is similar; thus the same approach to the management of poisoning can be used for both substances. Chloroquine is by and large an ingestant specific to low- and middle-income countries where malaria is endemic. France, however, is an exception to this rule; thus the French literature on chloroquine poisoning has made a substantial contribution to our understanding of this life-threatening condition. This fact has been attributed to the publication of a French book in 1982 entitled Suicide Mode de Emploi , which advocated chloroquine as a means of taking one’s life.

At the cellular level chloroquine, like quinidine, has membrane-stabilizing effects on the myocardium. Chloroquine is postulated to block voltage-gated myocardial ion channels involving Ca ²⁺ , Na ⁺ and K ⁺ . This subsequently leads to negative inotropy, slowed conduction and a higher electrical threshold for depolarization within the myocardium. Chloroquine is also believed to have some vasodilatory action; however, it is the effects on cardiac electrophysiology that make it a potentially lethal ingestion and one of the classic ‘drugs that kill’ when ingested in overdose.