A specific, sensitive, and accurate assay for diazoxide in human plasma and urine samples was developed utilizing stable-isotope dilution-GC-mass fragmentography. 3-Trideuterodiazoxide (d3-diazoxide) served as internal standard, and diazoxide wasN-methylated with diazomethane prior to GC. Plasma elimination half-lives of diazoxide ranged within 20–53 hr in four severely hypertensive patients, which did not correlate with endogenous plasma creatinine levels. A rapid infusion over 10–15 sec of an antihypertensive dose presumably resulted in a very transient precipitation of diazoxide due to its limited solubility of approximately 380 Μg/ml plasma. Urinary excretion accounted for 4–6 of the dose within 24 hr after administration in the four patients studied and totalled 19 and 22 in two patients. Renal clearance of diazoxide was below 1 ml/min on the first day following administration and increased to 2–3 ml/min on consecutive days. It was concluded that renal excretion of diazoxide is self-limited by antihypertensive doses in severely hypertensive patients. The major route of elimination in these patients may be due to me
展开▼
