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Notice to Readers Pentamidine Methanesulfonate to be Distributed by CDC

Pentamidine is used to treat patients with Pneumocystis carinii pneumonia (PCP) who have failed to respond or who have had adverse reactions to trimethoprim/sulfamethoxazole. Because of the unavailability of an approved product and the infrequent demand for the drug in the United States, CDC has supplied pentamidine through its Parasitic Disease Drug Service as an Investigational New Drug. The current incidence of acquired immunodeficiency syndrome (AIDS) has created an unprecedented demand for pentamidine (approximately 60% of AIDS patients develop PCP).

Starting in late May or early June 1984, CDC will distribute pentamidine methanesulfonate instead of pentamidine isethionate. Physicians and pharmacists should be aware of the change, because the dosages of the two pentamidine salts are calculated differently (Table 1). The change from one pentamidine salt to another is necessary because CDC has been unable to obtain assurances that the manufacturer of the isethionate salt can meet the increasing U.S. demand for pentamidine.

The indications for using pentamidine methanesulfonate are the same as those for pentamidine isethionate. Physicians in France and Canada have used pentamidine methanesulfonate to treat AIDS patients with PCP. Although results of such therapy have not been published, conversations by CDC with Canadian physicians concerning the outcomes of 13 AIDS patients with PCP treated with pentamidine methanesulfonate indicate that the efficacy and toxicity of the methanesulfonate salt appear similar to those of the isethionate salt. One published report has suggested that hypoglycemia occurs more commonly with pentamidine methanesulfonate than with pentamidine isethionate, but the number of patients described was small (1). The LD((50)) for mice is approximately the same for the two salts (2).

The doses of the two drugs are calculated differently because of the way the manufacturers have labeled their products (Table 1). Pentamidine isethionate is labeled to reflect the weight of salt present (pentamidine base moiety plus isethionate salt moieties), whereas pentamidine methanesulfonate is labeled according to the weight of only the pentamidine base present. Thus, 2.3 mg/kg of pentamidine base is equivalent to 4.0 mg/kg of pentamidine isethionate salt. Each ampule of pentamidine methanesulfonate solution contains the equivalent of 120 mg of pentamidine base dissolved in 3.0 ml of sterile water for injection. Expressed in terms of volume, the dose of pentamidine methanesulfonate is 0.0575 ml/kg.

The procedure for obtaining pentamidine methanesulfonate from CDC will be the same as that used in the past to obtain pentamidine isethionate. Reported by Div of Anti-Infective Drug Products, National Center for Drug and Biologics, US Food and Drug Administration; Div of Parasitic Diseases, Center for Infectious Diseases, CDC.


  1. Belehu A, Naafs B. Diabetes mellitus associated with pentamidine mesylate (Letter to the Editor). Lancet 1982;I:1463-4.

  2. Specia, Paris, France. Unpublished data.

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