benzylpenisilliini

Benzylpenicillin, also known as penicillin G or benzylpenicillin G, is a beta-lactam antibiotic in the penicillin class. It is produced by the fungus Penicillium chrysogenum and is one of the earliest antibiotics discovered and used clinically.

Mechanism of action

Benzylpenicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, which disrupts peptidoglycan cross-linking. This leads to weakening of the cell wall and, in many bacteria, cell lysis. The effect is time-dependent and requires adequate concentrations above the pathogen’s minimum inhibitory concentration.

Spectrum and administration

Benzylpenicillin is a narrow-spectrum antibiotic with activity primarily against many Gram-positive cocci and certain Gram-positive bacilli. It has limited activity against beta-lactamase–producing organisms and is not reliable against most Gram-negative bacteria or MRSA. Because it is acid-labile, benzylpenicillin is not effective when taken orally and is given parenterally, usually by intramuscular or intravenous injection. It exists in several salt forms, including sodium or potassium penicillin G, and long-acting formulations such as benzathine penicillin G and procaine penicillin G are used for specific indications.

Pharmacokinetics and safety

After intramuscular administration, benzylpenicillin achieves therapeutic plasma levels but has a relatively short half-life, necessitatingq frequent dosing or specialized formulations. It is primarily excreted unchanged by the kidneys. Adverse effects range from mild hypersensitivity reactions to severe anaphylaxis; cross-reactivity with other beta-lactams can occur. Prolonged use or high doses can lead to superinfections, and seizures may occur in overdose or renal impairment.

Clinical uses

Benzylpenicillin remains a standard treatment for susceptible streptococcal infections and certain syphilis regimens (e.g., benzathine penicillin G for some stages). Resistance and allergy considerations guide its use today, often favoring alternative antibiotics when indicated.