Distribution and Excretion of Doxycycline in Man

Abstract

The behavior of doxycycline was studied in 6 healthy subjects; this new antibiotic is obtained by hydrogenation of methacycline. Doxycycline differs from the other tetracyclines by an appreciably longer serum half-life, reaching 22.2 hr. Twenty-four hr. after the ingestion of 200 mg of this drug, the antibiotic serum levels are still 1.45 [mu]g/ml, which permits the consideration of treatments involving a single dally dose, considerably lower than those that are employed for other tetracyclines. Serum protein-binding varies between 25 and 31%. The excretion in 72 hr. is 39.6% by the urine, 4.9% by the stools; approximately half of the ingested dose is probably transformed in the body and in the bowel into bacteriologically inactive derivatives. The renal clearance of doxycycline varies at times between 33 and 22ml/min. Nearly 70% of the quantity filtered by the glomeruli is reabsorbed by the renal tubules.