Does Your Patient Need Penicillin?

This Post is adapted from the Canadian Pharmacists Association (CPhA) Drug Monograph: Penicillin G/Penicillin V

Product Summary Table

Pharmacology

• Penicillins G and V, known as the natural penicillins, are bactericidal against susceptible organisms.
• Penicillins interfere with the synthesis of cell wall mucopeptides, resulting in the formation of defective cell walls that will lyse and eventually result in death of the organism.
• The spectra of activity of penicillins G and V are similar:
  • Penicillin G is more active against gram-negative organisms (e.g., Neisseria) and some anaerobes than is penicillin V.
  • Penicillin G can be given parenterally, enabling the attainment of high serum concentrations, and is used for the treatment of serious infections involving penicillin-susceptible bacteria.
  • Penicillin V is more resistant to hydrolysis by acidic gastric secretions and is absorbed orally to a much greater extent than penicillin. Currently, only penicillin V is available orally, for the treatment of penicillin-susceptible infections of mild to moderate severity, in which the oral route of administration is desirable.

Indications

• Drug of choice for the following infections: actinomycosis, streptococcal pharyngitis, erysipelas, erysipeloid, leptospirosis, trench mouth, syphilis, bejel, pinta, yaws, clostridial and streptococcal necrotizing infections, P. multocida infections, leptospirosis, rat-bite fever and the prophylaxis of rheumatic fever.
• Penicillin G: treatment of infections due to susceptible organisms of moderate to severe infections. 
• Penicillin V : treatment of mild to moderately severe infections. 
• Penicillin G benzathine: moderately severe infections that respond to low levels of penicillin.
• Penicillin G and penicillin V: treatment of: actinomycosis caused by Actinomyces species; anthrax caused by B. anthracis; bronchitis, acute otitis media, pharyngitis, sinusitis, skin and soft tissue infections caused by susceptible organisms; erysipelas caused by susceptible strains of group A streptococci; erysipeloid (including endocarditis and septicemia) caused by E. rhusiopathiae; acute, necrotizing, ulcerative gingivitis (Vincent’s angina or “trench mouth”) caused by anaerobes and spirochetes; P. multocida infections; rat-bite fever caused by S. moniliformis or S. minor; scarlet fever caused by group A streptococci; Lyme disease caused by B. burgdorferi.
• Penicillin V: prophylaxis of rheumatic fever caused by group A streptococci.
• Penicillin V: reduce the incidence of S. pneumoniaesepticemia in children >5 years with sickle cell anemia.
• Parenteral penicillin G: treatment of bone and joint infections, bacterial endocarditis, intra-abdominal infections, meningitis, pericarditis, pneumonia and septicemia caused by susceptible organisms; listeriosis caused by L. monocytogenes; tetanus; yaws caused by T. pallidum pertenue; tertiary and neurosyphilis; gas gangrene caused by Clostridium species; leptospirosis caused by Leptospira species; diphtheria caused by C. diphtheriae, as an adjunct to antitoxin.
• Penicillin G benzathine: treatment of bejel caused by T. pallidum endemicum, pinta caused by T. carateum and yaws caused by T. pertenue. Penicillin G benzathine is also used for the treatment of pharyngitis and early or late benign syphilis (not neurosyphilis) and in the prophylaxis of diphtheria and recurrent rheumatic fever.

Warnings

• Serious and occasionally fatal hypersensitivity reactions have been reported in patients receiving penicillin therapy. Although anaphylaxis is more frequent following parenteral therapy, it has occurred in patients receiving oral penicillin.
• Cross-sensitivity between penicillins and cephalosporins is estimated to be very low, expected to be highest with  first-generation cephalosporins.