THE RELATIVE EFFICACY OF ANTIDOTES

For marry physicians an antidote is an antidote. According to the Inte rnational Programme on Chemical Safety definition, an antidote is a th erapeutic substance used to counteract the toxic action(s) of a specif ied xenobiotic. Given this wide definition, the efficacy of an antidot e may vary considerably depending on which toxic action(s) being count eracted mid the level of counteracting power. An almost 100% efficacy is seen using specific antagonists, such as naloxone in opiate poisoni ng or flumazenil in benzoniazepine poisoning, e.g. resulting in comple te reversal of opiate toxicity unless complications, such as anoxic br ain damage, have developed. At the other end of the efficacy scale, we may place chelating agents for heavy metal poisoning and diazepam for orgamophosphorus insecticide poisoning which are considered only to b e an adjuncts to supportive care. When teaching clinical toxicology or recommending the use of antidotes in poisoned patients, the expected efficacy level of the antidote in question should be stressed. This ma y be particularly important in severe poisonings when the antidote may only be considered as an important adjunct to supportive care, e.g. d eferoxamine in acute iron poisoning. Unless this is stressed, the unex perienced physician may rely too much on the antidote and pay insuffic ient attention to the supportive care. The varying efficacy levels wil l be discussed based on the presently ongoing International programme on Chemical Safety/Commission of the European Communities evaluation p rogram on antidotes.