Question

• a) Penicillin mechanism of Action

• b) Penicillin Indications

• c) Penicillin Contraindications

Answer 1

Penicillin mechanism of Action

Penicillin prevents peptidoglycan from cross-linking properly in the last stages of bacterial cell wall synthesis. This greatly weakens the cell wall and causes the bacterium to lyse, or burst open, because of osmotic pressure. Penicillin is bactericidal because it directly kills bacteria.

Penicillin: Indications

Benzylpenicillin administered intravenously is the drug of choice for bacterial meningitis if this disease is caused by sensitive strains of meningococci or pneumococci. Further important indications for an intravenous penicillin treatment are endocarditis caused by Streptococcus viridans, other hazardous streptococcal infections (severe pneumonia, arthiritis), neurosyphilis, actinomycosis, anthrax and clostridium infections.

Smaller doses are administered intramuscularly. A streptococcal pharyngitis can be treated with a single injection of a benzylpenicillin slow release preparation (if available). Erysipelas, fusospirochaetes angina (Vincent's angina), diphtheria, pneumococcal pneumonia and primary syphilis infections can also be treated intramuscularly. Secondary prophylaxis of rheumatic fever has become very rare.

Orally administered phenoxymethylpenicillin is a 'painless' alternative for streptococcal angina and other indications of the intramuscular therapy, as well as dog and cat bites. It can be considered in the early stages of Lyme disease if doxycycline is contraindicated

Penicillin Contraindications

hypersensitivity to penicillin