phenoxymetylpenicillin

Phenoxymethylpenicillin, commonly called penicillin V, is an acid-stable beta-lactam antibiotic in the penicillin class. It is produced by certain fungi and is used to treat infections caused by susceptible organisms, with a particular emphasis on streptococcal infections. Its acid stability makes it suitable for oral administration.

Mechanism of action: It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, preventing peptidoglycan cross-linking and causing bacterial lysis. It is bactericidal against susceptible organisms in appropriate conditions.

Spectrum: It has a narrow spectrum, with good activity against many Gram-positive cocci, including Streptococcus species, and some Gram-positive anaerobes. It has limited activity against Gram-negative bacteria and is inactivated by most beta-lactamases; therefore it is not effective against penicillinase-producing pathogens.

Pharmacokinetics: Penicillin V is well absorbed from the gastrointestinal tract, though absorption is reduced by food. Peak levels occur within one to two hours. The drug has a short elimination half-life (roughly 30–60 minutes) and is mainly excreted by the kidneys, requiring dose adjustment in renal impairment.

Indications: It is used for mild-to-moderate infections caused by susceptible organisms, such as streptococcal pharyngitis and tonsillitis, dental infections, and certain skin and soft tissue infections. It has been used for prophylaxis in selected patients, including rheumatic fever prophylaxis and dental procedures in certain high-risk individuals.

Contraindications and adverse effects: The major contraindication is hypersensitivity to penicillins or other beta-lactams. Cross-sensitivity with cephalosporins can occur. Common adverse effects include rash, hypersensitivity reactions, gastrointestinal upset, diarrhea, and, rarely, superinfections.

Interactions: May reduce the effectiveness of oral contraceptives; may interact with allopurinol, increasing the risk of rash; cholestyramine can interfere with absorption. Dose adjustments may be required in renal impairment.