Penicillin V potassium is bactericidal against penicillin-susceptible microorganisms during the stage of active multiplication. It produces its effect by inhibiting biosynthesis of cell-wall mucopeptide. It is not active against the penicillinase-producing bacteria, which include many strains of staphylococci. The drug exerts high in vitro activity against staphylococci (except penicillinase-producing strains), streptococci (groups A, C, G, H, L, and M), and pneumococci. Other organisms susceptible in vitro to penicillin V areCorynebacterium diphtheriae, Bacillus anthracis, clostridia,Actinomyces bovis, Streptobacillus moniliformis, Listeria monocytogenes, Leptospira, and Neisseria gonorrhoeae.Treponema pallidium is extremely susceptible.

Penicillin V potassium has the distinct advantage over penicillin G in being resistant to inactivation by gastric acid. It may be given with meals; however, blood levels are slightly higher when the drug is given on an empty stomach. Average blood levels are 2 to 5 times higher than those following the same dose of oral penicillin G and also show much less individual variation.

Once absorbed, about 80% of penicillin V potassium is bound to serum protein. Tissue levels are highest in the kidneys, and lesser amounts appear in the liver, skin, and intestines. Small concentrations are found in all other body tissues and the cerebrospinal fluid. The drug is excreted as rapidly as it is absorbed in individuals with normal kidney function; however, recovery of the drug from the urine indicates that only about 25% of the dose given is absorbed. In neonates, young infants, and individuals with impaired kidney function, excretion is considerably delayed.

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