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Benzylpenicillin

Injectable penicillin antibiotic.

Clinical information

Common uses

bacterial infections, including syphilis and other spirochaetal infections

Common side effects

allergic reactions such as hives and itching
temporary fever-chills reaction when treating syphilis

Cautions

serious, occasionally fatal allergic reactions possible
tell your doctor about penicillin or cephalosporin allergy
antibiotic-associated C. difficile diarrhoea can occur

Interactions

chloramphenicol, erythromycin, sulfonamides, tetracyclines (may blunt effect)
probenecid (raises and prolongs penicillin levels)
aspirin, indomethacin, thiazide diuretics, furosemide (prolong levels)

Pregnancy: no evidence of harm — use only if needed

Reference information, not medical advice — always follow your doctor or pharmacist. Source: DailyMed, dailymed.nlm.nih.gov, penicillin G potassium injection label, setid 9e58122f-5c75-4905-a774-d3a4dae4ff8c (accessed 2026-08-16)

Approved brands & formulations1

Brand name	Dosage form	Strength	Importer	Category
Benzylpenicillin	Parenteral ( Injection )	Powder for injection: 600 mg (= 1 million IU); 3 g (= 5 million IU) (sodium or potassium salt) in vial	MFDA designated importers with Pre Authorization approval before import	hospital