Pharmacokinetics of nalidixic acid associated with sodium citrate

A pharmacokinetic study of sachets containing nalidixic acid (0.66 g) associated with sodium citrate (3.75 g)--NSC--was carried out in 10 healthy volunteers in order to determine the influence of the urine alcalinization due to sodium citrate on the elimination of nalidixic acid (NA) and its 7-hydroxy (HNA) and 7-carboxy (CNA) derivatives. Urine alcalinization enhanced markedly the urinary excretion of HNA, but not of NA and CNA. The urinary concentrations of bacteriologically active compounds--NA + HNA--remained above five times their minimum inhibitory concentration for 10 h following each dose. After a 3-day treatment using NSC three times daily there was no significant accumulation of NA and derivatives in the plasma and no significant change in their kinetics. Finally, from a pharmacokinetic viewpoint, the daily administration of 3 sachets of NSC each containing 0.66 g of NA seems valuable in the treatment of urinary tract infections.