The disposition profile of ceftriaxone was studied in eight normal subjects and in 15 subjects with various degrees of chronic liver damage (alcoholic fatty liver [FL] and cirrhosis without [C] and with [CA] ascites) who received bolus injections of ceftriaxone, 1 gm iv. Plasma protein binding fell in all. As a result, mean free fraction in plasma rose between 140% (FL) and 320% (CA). An exceptionally large rise (1270%) occurred in one subject with CA when the condition was aggravated by renal impairment. Fourteen of 15 subjects had renal clearance of unbound drug of the same order as that in healthy adults. In chronic liver disease, mean nonrenal clearance of unbound drug fell with severity of liver damage. Kinetic parameters with reference to total drug differed in normal subjects and subjects with CA. Kinetic changes in the latter were such that elimination t 1/2 beta did not differ (9.7 and 8.4 hr). Because of the wide therapeutic range of ceftriaxone, subjects with chronic liver disease would require no dose adjustments, whereas dose reductions are envisaged for subjects with cirrhosis (C,CA) on the basis of increased unbound drug concentrations.

The kinetics and binding parameters of ceftriaxone have been characterized in eight normal subjects who received, in sequence, 1.0 g ceftriaxone and 1.0 g ceftriaxone together with 250 and 500 mg probenecid q.i.d. Probenecid increased the total systemic clearance (CLTS) from 0.244 to 0.312 ml/min/kg, whereas the terminal half-life (t1/2T (beta)) fell from 8.1 to 6.5 h. In contrast, the renal clearance of free ceftriaxone (CLFR) was decreased from 2.09 to 1.67 ml/min/kg, confirming a small but significant contribution of tubular secretion to the renal elimination of ceftriaxone. The final value of CLFR was attained with the lower dose probenecid, whereas the non-renal clearance of free ceftriaxone (CLFNR) fell progressively from 2.78 to 1.90 ml/min/kg with the increasing probenecid dose. The total decrease in the systemic clearance of free ceftriaxone (CLFS) after the higher dose of probenecid was about 30% (4.87 to 3.57 ml/min/kg). As a consequence of a decreased affinity constant (KA), the average free fraction in plasma (f) was increased by 54% after the low dose and by 74% after the high dose of probenecid. The protein binding interaction between probenecid and ceftriaxone appears to be unique. The results are of limited clinical consequence for ceftriaxone but they emphasise the importance of evaluating the kinetics of the free drug when examining interactions involving probenecid.

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The pharmacokinetics of glibornuride (25 mg i.v.) and the accompanying insulin and glucose responses were characterized in eight human subjects in the presence and absence of steady‐state tenoxicam (20 mg p.o./day for 2 weeks). Tenoxicam affected neither the pharmacokinetic parameters of glibornuride (systemic clearance, volume of distribution and biological half‐life) nor the responses of plasma insulin and blood glucose to glibornuride. The single i.v. dose of glibornuride had no detectable effect on the kinetics of tenoxicam.