Antidotes: a superb review
February 25, 2012, 3:20 pm
Antidotes for toxicological emergencies: A practical review. Marraffa JM et al. Am J Health-Syst Pharm 2012 Feb 1;69:199-212.
Although aimed primarily at hospital pharmacists, this superb review of the major toxicological antidotes would also be helpful reading for emergency physicians and nurses. The authors provide focused intelligent sections on toxic-alcohol poisoning, antidotes for calcium-channel blocker and β-blocker overdose, the cyanide kit and hydroxocobalamin, digoxin-specific Fab fragments, flumazenil, intravenous fat emulsion, N-acetylcysteine, naloxone, and octreotide.
My only major area of disagreement with the authors concerns their discussion of naloxone. They don’t clearly distinguish between the two types of clinical scenarios in which naloxone might be considered: 1) the crashing patient with respiratory depressions and suspected opiate overdose; and 2) the stable patient with mild opiate effects. Similarly to the current edition of Goldfrank’s Toxicologic Emergencies, the recommend starting naloxone at a dose of 0.04 to 0.05 mg, and then “adjust[ing] the dose upward in increments of 0.04-0.05 mg. (One of the co-authors of this paper, Mary Ann Howland, is an editor of the Goldfrank text.) This seems to me inappropriate. In the crashing patient, one would want to get a substantial dose of naloxone on board rather quickly. Since some opiate-toxic patients require up to 10 mg, repeating a dose of 0.05 mg every minute would take over 3 hours. (To be fair, later in their discussion they change the recommendation to “doubling the dose every one to two minutes or escalating the dose from 0.05 mg to 0.1 mg to 0.4 mg to 2 mg to 10 mg.) In the mildly symptomatic opiate patient, in my opinion before giving the almost homeopathic dose of 0.05 mg one should question whether naloxone is needed at all. If one does elect to give it, a very attractive alternative would be by the inhalation route, which minimizes the chance of precipitating acute withdrawal. Unfortunately, the authors don’t discuss this route at all.