An 18-year-old man who is known to have non-penicillinase producing gonococcal urethritis is given an injection of penicillin and probenecid. What is the mechanism used by probenecid that makes penicillin more efficacious
Prolongs the duration of action by affecting the liver metabolism of penicillin
Increases the half-life and serum level by decreasing the renal excretion of penicillin
Promotes entry of the penicillin into the bacteria
Decreases the bacterial resistance by inhibiting penicillinase production
PENICILLIN-G (BENZYL PENICILLIN) Pharmacokinetics :- Penicillin G is acid labile, therefore destroyed by gastric acid. As such, less than 1/3rd of an oral dose is absorbed in the active form. Absorption of sod. PnG from i.m. site is rapid and complete; peak plasma level is attained in 30 min. It is distributed mainly extracellularly; reaches most body fluids, but penetration in serous cavities and CSF is poor. However, in the presence of inflammation (sinovitis, meningitis, etc.) adequate amounts may reach these sites. About 60% is plasma protein bound. It is little metabolized because of rapid excretion. The pharmacokinetics of PnG is dominated by very rapid renal excretion; about 10% by glomerular filtration and the rest by tubular secretion. The plasma t 1/2 of PnG in healthy adult is 30 min. Neonates have slower tubular secretion-- t 1/2 of PnG is longer; but approaches adult value at 3 months and then is even shoer during childhood. Aged and those with renal failure excrete penicillin slowly. Tubular secretion of PnG can be blocked by probenecid--higher and longer lasting plasma concentrations are achieved. Probenecid also decreases the volume of distribution of penicillins. Ref:- kd tripathi; pg num:-718
Antibiotics