Penicillin G Procaine

What it is and how it works

Procaine benzylpenicillin is a poorly soluble salt that slowly releases benzylpenicillin from the intramuscular depot, giving prolonged low-to-moderate plasma concentrations. Benzylpenicillin inhibits bacterial cell-wall peptidoglycan synthesis by binding penicillin-binding proteins, causing bactericidal effects.

Indications

Infections caused by penicillin-susceptible organisms where prolonged moderate levels are adequate, including syphilis (including neurosyphilis with probenecid and congenital syphilis), anthrax, and some streptococcal and pneumococcal infections.

Dosage and administration (summary)

Deep intramuscular injection only, usually 600,000–1.2 million units once daily (e.g. early syphilis 1.2 million units daily for 10 days per WHO guidance), with duration depending on the infection.

Contraindications

Hypersensitivity to penicillins or to procaine; never give intravenously.

Warnings and precautions

Inadvertent intravascular injection may cause serious neurovascular damage or acute procaine reactions (Hoigné syndrome) with anxiety, hallucinations and seizures. Anaphylaxis may occur in penicillin-allergic patients; ask about allergy and observe after injection. Jarisch-Herxheimer reaction may occur at the start of syphilis treatment.

Pregnancy

Penicillins are considered safe in pregnancy and are the treatment of choice for syphilis in pregnancy.

Storage and supply

Store at 2–8 °C in a refrigerator (ready-made suspensions) or below 25 °C for dry powder, according to the product.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.