Biphasic dysglycemia induced by pentamidine and detected by intermittently scanned continuous glucose monitoring: a case report of a possible drug-drug interaction with clopidogrel and literature review.

backgroundPentamidine is an alternative treatment for Pneumocystis pneumonia (PCP) in patients who are intolerant to sulfamethoxazole-trimethoprim; however, its use is limited by serious adverse effects, including glycemic fluctuations. Herein, we report a case in which intermittently scanned continuous glucose monitoring (isCGM) was used to monitor real-time glycemic fluctuations during pentamidine therapy, enabling successful completion of treatment. To contextualize this case, we also conducted a targeted literature review of pentamidine-induced glucose dysregulation. CASE PRESENTATION: An 86-year-old Japanese man undergoing immunosuppressive therapy for rheumatoid arthritis was diagnosed with PCP and initially treated with sulfamethoxazole-trimethoprim. Because of suspected adverse effects of sulfamethoxazole-trimethoprim, the patient was switched to intravenous pentamidine as second-line therapy. Given the risks associated with advanced age, abnormal kidney function, and concomitant use of clopidogrel, an organic cation transporter 1 (OCT1) inhibitor that may affect pentamidine disposition, glycemic monitoring was initiated using isCGM. The patient experienced nocturnal hypoglycemia soon after initiating pentamidine treatment, which persisted after pentamidine discontinuation. He subsequently developed marked hyperglycemia associated with impaired endogenous insulin secretion, necessitating temporary regular insulin administration and sitagliptin combination therapy. His glycemic control gradually stabilized, and recovery of pancreatic β-cell function was confirmed by increased urinary C-peptide levels. In a literature review of 83 reports published between 1995 and 2025, only nine cases of pentamidine-associated dysglycemia were identified, and this was the only case that demonstrated biphasic glucose dysregulation with both hypoglycemia and hyperglycemia.

conclusionThis case demonstrates that biphasic glucose dysregulation associated with pentamidine (early hypoglycemia followed by delayed-onset hyperglycemia) can be captured using isCGM. Real-time glucose monitoring during pentamidine therapy enabled early intervention and safe completion of treatment. Glycemic monitoring using isCGM may be beneficial in patients receiving pentamidine, especially those with abnormal kidney function, older patients, or those receiving concomitant OCT1 inhibitor therapy.