Comparative pharmacokinetics of doxycycline and oxytetracycline in patients with hyperlipidemia

This study examines the pharmacokinetics of lipophilic drug doxycycline (Vibramycin) and water-soluble antibiotic oxytetracycline hydrochloride (Oxyterracyna) in patients with hyperlipidemia type IIa and type IV according to Fredrickson. Antibiotics were administered orally as a single dose and determined in plasma by a fluorimetric method. The calculations were performed by aid of a computer. Increased concentrations of doxycycline were found; they were higher in type IIa, as compared with type IV. Area under the curve (AUC) and peak concentrations as well as rate constant for elimination in subjects with type IV were significantly elevated; volumes of distribution and total body clearance were markedly diminished. Decreased concentrations of oxytetracycline, area under the curve, peak concentration and rate constant for elimination were observed in patients with type IV. In both types of hyperlipidemia volume of distribution was increased and half-life in patients with type IV was significantly prolonged. The findings show that hyperlipidemia can be an important factor of drug action. Alterations of pharmacokinetics of lipophilic doxycycline and hydrophilic oxytetracycline were contrasting.