Pharmacokinetics of Sulbactam/Ampicillin in Humans after Intravenous and Intramuscular Injection

We investigated the pharmacokinetic properties of sulbactam/ampicillin (S/A), after intravenous (0.5/1.0 and 1.0/2.0 g) and intramuscular (0.5/1.0 g) coadministration in 10 male subjects. After 1.0/2.0 g intravenous doses of S/A the half-lives (t( 1/2 β)) were 1.14 ± 0.14/1.09 ± 0.16 h. The values for plasma clearance (Cl(p)) were 198.83 ± 26.27/250.33 ± 39.28 ml/min and the renal clearance (Cl(r)) 173.50 ± 19.66/208.80 ± 26.43 ml/min. The post distributive volumes (V(β)) were 19.67 ± 3.24/23.56 ± 5.76 liters. Similar values were obtained after 0.5/1.0 g of S/A intravenous coinjection. After 0.5/1.0 g intramuscular coadministration the t( 1/2 β) values were 1.26 ± 0.18/1.20 ± 0.15 h. The values for Cl(p) were 208.00 ± 28.73/243.17 ± 33.24 ml/min, for Cl(r) 179.50 ± 20.26/202.67 ± 27.61 ml/min and for V(β) 22.27 ± 4.12/25.30 ± 4.87 liters. The renal clearance of sulbactam is comparable to that of ampicillin and both clearances are greater than the glomerular filtration rate, suggesting active renal tubular secretion of the two drugs. The large volumes of distribution, and the ratio K12/K21 = 0.5 show the extensive distribution of the two drugs into extracellular fluids. The very similar values of the pharmacokinetic parameters of sulbactam and ampicillin confirm that the kinetics of the two drugs closely resemble one another.