Netherlands. The need for caution when prescribing or dispensing antimalarial drugs is illustrated by three case studies (2).

Case 1. A 45-year old woman was prescribed mefloquine (Lariam) 1,250 mg and primaquine 1,260 mg (84 tablets) for Plasmodium vivax malaria. Primaquine was then also given at a dose of 15 mg daily for the next five days. On day two of treatment, the patient developed acute liver failure: primaquine overdose was not identified as the cause until 6 months later. Note: The recommended treatment for P. vivax malaria is chloroquine 1,500 mg over three days followed by primaquine 15 mg daily for 14 to 21 days. The reporting doctor comments that this case reinforces the need for expertise in malaria treatment as well as vigilance by nursing and pharmacy personnel.

Cases 2 and 3. Mefloquine (Lariam) was dispensed in lieu of terbinafine (Lamisil). In both cases, the total dose of mefloquine received exceeded 15,000 mg. Symptoms of toxicity resolved after approximately one year. The authors comment that, as well as demonstrating the wide therapeutic margin of mefloquine, these cases illustrate the potential for medication error with these two similarly named 250-mg tablets.

References:

1) The Pharmaceutical Journal 261, p. 764, 14 November 1998.
2) Lobel HO, Coyne PhE & Rosenthal Ph. Drug Overdoses with antimalarial agents: prescribing and dispensing errors. Journal of the American Medical Association 280: 1483, 1998.