Bepen Mechanism of Action

Pharmacology: Pharmacodynamics: General Properties: Benzylpenicillin sodium BP is a beta-lactam antibiotic. It is bactericidal by inhibiting bacterial cell wall biosynthesis.
Breakpoints: The tentative breakpoints (British Society for Antimicrobial Chemotherapy, BSAC) for Benzylpenicillin sodium BP are as follows: (See Table 1.)

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Susceptibility: The prevalence of resistance may vary geographically and with time for selected species and local information on resistance is desirable, particularly when treating severe infections. The following table gives only approximate guidance on probabilities whether microorganisms will be susceptible to Benzylpenicillin sodium BP or not. (See Tables 2 and 3.)

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Other Information: Known Resistance Mechanisms and Cross-resistance: Penicillin resistance can be mediated by alteration of penicillin binding proteins or development of beta-lactamases.
Resistance to penicillin may be associated with cross-resistance to a variety of other beta-lactam antibiotics either due to a shared target site that is altered, or due to a beta-lactamase with a broad range of substrate molecules. In addition to this, cross-resistance to unrelated antibiotics can develop due to more than one resistance gene being present on a mobile section of DNA (e.g. plasmid, transposon etc) resulting in two or more resistance mechanisms being transferred to a new organism at the same time.
Pharmacokinetics: Benzylpenicillin sodium BP rapidly appears in the blood following intramuscular injection of water-soluble salts and maximum concentrations are usually reached in 15-30 minutes. Peak plasma concentrations of about 12 mcg/mL have been reported after doses of 600 mg with therapeutic plasma concentrations for most susceptible organisms detectable for about 5 hours. Approximately 60% of the dose injected is reversibly bound to plasma protein.
In adults with normal renal function, the plasma half-life is about 30 minutes. Most of the dose (60-90%) undergoes renal elimination, 10% by glomerular filtration and 90% by tubular secretion. Tubular secretion is inhibited by probenecid, which is sometimes given to increase plasma penicillin concentrations. Biliary elimination of Benzylpenicillin sodium BP accounts for only a minor fraction of the dose.