Pentamidine-induced beta cell toxicity is not preventable by high glucose

Effect of cimetidine on pentamidine induced hyperglycemia in rats

The antiprotozoal agent pentamidine, used for the treatment of Pneumocystis jirovecii pneumonia (PCP), is known to cause abnormalities in blood glucose homeostasis, such as hypoglycemia and hyperglycemia. Pentamidine has been reported to be a substrate of organic cation transporter 1 (OCT1). We investigated the combination effects of cimetidine, an OCT1 inhibitor, on the pharmacokinetics of pentamidine and on pentamidine-induced hyperglycemia. Pentamidine was infused intravenously to rats for 20 min at a dose of 7.5 or 15 mg/kg and serum samples were obtained periodically. The serum concentration of glucose did not change significantly after pentamidine infusion at 7.5mg/kg, while it increased with pentamidine at 15 mg/kg, and the maximal concentration of glucose was 167 ± 36 mg/dl, 30 min after the start of pentamidine infusion. Cimetidine (50mg/kg) enhanced the pentamidine-induced elevation of glucose concentration and the maximal concentration of glucose was 208 ± 33 mg/dl in the pentamidine 15 mg/kg treated group. Cimetidine combination significantly reduced total body clearance of pentamidine and increased pentamidine concentrations in the liver, kidneys, and lungs. A significant correlation was found between changes in serum glucose concentrations and serum concentrations of pentamidine 30 min after the start of pentamidine infusion. These results suggest that the hyperglycemic effect of pentamidine is dependent on the concentration of pentamidine and can be enhanced by cimetidine combination.

Characterization of glucose-6-phosphatase in hepatocytes. Effects of amiloride and pentamidine

The hepatic microsomal glucose-6-phosphatase enzyme is situated inside the lumen of the endoplasmic reticulum and, for normal enzyme activity in vivo, three transport systems are needed for the substrate glucose-6-phosphate and the products phosphate and glucose. Previous studies using isolated microsomes showed that the drugs amiloride and pentamidine do not affect the glucose-6-phosphatase enzyme but can activate the glucose-6-phosphate transport system. Here we demonstrate that, very surprisingly, the addition of pentamidine (and to a lesser extent amiloride) to isolated hepatocytes results in an inhibition of the catalytic subunit of glucose-6-phosphatase.

Pentamidine activates T1 the hepatic microsomal glucose 6-phosphate transport protein of the glucose-6-phosphatase system

The mechanism of activation of hepatic microsomal glucose-6-phosphatase (EC 3.1.3.9) in vitro by pentamidine has been investigated in both intact and fully disrupted microsomes. The major effect of pentamidine is a 4.7-fold reduction in the Km of glucose-6-phosphatase activity in intact diabetic rat liver microsomes. The site of action of pentamidine is T1 the hepatic microsomal glucose 6-phosphate transport protein. The activation of T1 by pentamidine may contribute to the disturbed blood glucose homeostasis seen in many patients after the administration of the drug pentamidine.

Pentamidine: a review

With the advent of the acquired immunodeficiency syndrome (AIDS), the therapeutic importance of pentamidine isethionate has increased greatly. This review summarizes the pharmacology, clinical experience in the treatment of Pneumocystis carinii pneumonia, and toxicity of pentamidine. Data are conflicting as to whether pentamidine is more or less effective than trimethoprim-sulfamethoxazole (TMP-SX) for the treatment of P carinii pneumonia in individuals with AIDS, but due to its toxicity and expense, it is considered as second-line therapy for P carinii pneumonia by many authorities. Hypoglycemia has been encountered in up to 27%, and nephrotoxicity in 25%, of treatment courses with pentamidine. In an attempt to circumvent the toxicities associated with parenteral administration, aerosolized delivery has been evaluated for both therapy and prevention of P carinii pneumonia. Aerosolized pentamidine, on the basis of early clinical results, convenience, and low toxicity, is being used extensively to prevent P carinii pneumonia in individuals at high risk. Relapses occur, however, and pneumothorax may be more common in those using this form of prophylaxis. Aerosolized pentamidine should not be used as sole therapy for acute P carinii pneumonia.