The effects of chronic renal insufficiency on the pharmacokinetics of doxycycline in man.

The pharmacokinetics as well as erythrocyte and plasma protein binding of doxycycline were studied in fifteen patients with various renal function impairments after oral doxycycline polyphosphate single administration. Plasma half-life (t 1/2), area under the plasma concentration-time curve (AUC), urinary excretion, renal clearance, erythrocyte and plasma protein binding (%) were regressed vs creatinine clearance. No significant correlations were observed between t 1/2 or AUC and renal function nor plasma protein binding and plasma albumin concentrations. Significant correlations were obtained between urinary excretion, renal clearance, erythrocyte binding, plasma protein binding and creatinine clearance. Significant correlation was obtained between haematocrit and erythrocyte binding. Constancy of overall elimination parameters in renal failure is due to parallel increase in plasma free fraction of doxycycline.