What are the effects and indications of penicillin?

Penicillin generally works by inhibiting bacterial cell wall synthesis, killing susceptible bacteria, preventing bacterial reproduction, reducing bacterial virulence, and enhancing therapeutic efficacy when used in combination with other drugs. It is primarily used to treat conditions such as hemolytic streptococcal infections, Streptococcus pneumoniae infections, Neisseria meningitidis infections, Treponema pallidum (syphilis) infections, and Clostridium tetani infections. A detailed analysis is as follows:

I. Mechanisms of Action

1. Inhibition of bacterial cell wall synthesis: Penicillin interferes with the synthesis of the bacterial cell wall, causing structural defects. This leads to bacterial lysis and death due to osmotic imbalance, thereby exerting a bactericidal effect.

2. Killing of susceptible bacteria: It is effective against various Gram-positive cocci, Gram-positive bacilli, and some Gram-negative cocci. Penicillin directly eliminates susceptible pathogens in the body and controls the spread of infection.

3. Prevention of bacterial replication: By disrupting bacterial structure, it prevents bacterial division and proliferation, reducing the overall bacterial load and alleviating inflammatory responses caused by infection.

4. Reduction of bacterial virulence: While killing bacteria, penicillin also reduces toxin production, minimizing tissue damage caused by toxins and relieving symptoms associated with infection.

5. Synergistic enhancement of efficacy with other drugs: When used in combination with certain antimicrobial agents, penicillin can enhance overall antibacterial effects, making it particularly suitable for treating severe or mixed infections.

II. Clinical Indications

1. Hemolytic streptococcal infections: Effective in treating pharyngitis, tonsillitis, scarlet fever, and erysipelas caused by hemolytic streptococci. It efficiently eliminates the causative pathogens and relieves symptoms.

2. Streptococcus pneumoniae infections: Used to treat pneumonia, otitis media, and sinusitis caused by S. pneumoniae. It helps control pulmonary and respiratory tract infections and improves respiratory function.

3. Neisseria meningitidis infections: Indicated for epidemic cerebrospinal meningitis caused by N. meningitidis. Penicillin can cross the blood-brain barrier to kill bacteria and reduce meningeal inflammation.

4. Treponema pallidum (syphilis) infections: The drug of choice for early-stage syphilis, penicillin effectively kills T. pallidum, controls disease progression, and prevents complications.

5. Clostridium tetani infections: Used in the treatment of tetanus to eliminate C. tetani from wounds and the body. When combined with tetanus antitoxin, it helps prevent worsening of the condition.

A skin allergy test must be performed before using penicillin; individuals with allergies should not use it. Penicillin must be taken strictly according to medical instructions regarding dosage and duration—do not adjust the dose or discontinue use without consulting a healthcare provider.