Evaluation of renal excretion and pharmacokinetics of furosemide in rats after acute exposure to high altitude at 4300 m.

With studies indicative of altered renal excretion under high altitude-induced hypobaric hypoxia, the consideration of better therapeutic approaches has long been the aim of research on the management of high altitude related illness. The pharmacokinetics of drugs such as furosemide might be altered under hypoxic conditions, making it essential to establish different dose-regimens to maintain therapeutic efficacy or to avoid toxic side effects at high altitude. Simultaneously, drug-drug interactions (DDIs) mediated by OAT1 occur at high altitude, severely affecting furosemide pharmacokinetics. This study investigated the influence of acute exposure to high altitude at 4300 m on the renal excretion of furosemide in rats. Significant changes in physiological parameters and kidney histopathology were found after acute high altitude exposure. Compared with low altitude, the pharmacokinetics of furosemide and the expression level of OAT1 in kidney were significantly changed after rapid ascent to high altitude. Additionally, the down-regulated OAT1 expression further sustained the potential mechanism for the decreased renal excretion of furosemide, resulting in extended residence of the drug in the human body. The elevation of AUC, Cmax , MRT, t1/2 of furosemide, and decreased CL at high altitude further reinforced the current findings. Moreover, the absorption of furosemide was markedly increased and renal excretion significantly declined after co-administration of captopril, resulting in local drug interaction at high altitude. In conclusion, acute exposure to high altitude may significantly affect the renal excretion of furosemide and the pharmacokinetic parameters of furosemide were altered after co-administration of captopril, which may then impact the conventional therapeutic dosage.