How do you take Benzylpenicillin sodium?

This drug is NOT a tablet or syrup; it must be given as an injection by a trained health worker at a hospital or clinic. The usual adult dose is 600mg to 1.2g (1 to 2 mega units) injected every 6 hours, but your doctor will decide the exact dose based on how serious your infection is. Do not try to inject yourself at home.

What are the side effects of Benzylpenicillin sodium?

Pain or swelling at the injection site, diarrhoea, mild skin rash, nausea or vomiting, mild fever

Who should not take Benzylpenicillin sodium?

Anyone who has ever had an allergic reaction to penicillin or any other penicillin-type antibiotic (like amoxicillin or ampicillin) should NOT take this drug. People with a history of severe allergic reactions to other antibiotics called cephalosporins should also inform their doctor before use.

Prescription

Antibiotic (Penicillin)

Benzylpenicillin sodium

Last reviewed July 2026

Who is this for?

For adults (18+). Standard adult dosing applies: see the How to Take tab for full instructions.

What is this drug?

Benzylpenicillin sodium (also called Crystalline Penicillin G) is an antibiotic that kills bacteria by breaking down their protective walls, stopping them from multiplying in your body.

How it works

Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins and preventing cross-linking of peptidoglycan strands, leading to cell wall rupture and bactericidal activity against susceptible gram-positive and gram-negative organisms.

What is it used for?

Serious bacterial infections like pneumonia, meningitis (brain infection), septicaemia (blood infection), throat infections, wound infections, sexually transmitted infections like syphilis and gonorrhoea, tetanus, and skin infections

Browse by condition

Bacterial Infections Skin Infections Pneumonia Meningitis Throat & Chest Infections STIs & Sexual Health Sepsis & Severe Infections Syphilis Throat & Tonsil Infections

Prescription Required

You need a doctor's prescription to buy this drug.

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What to watch out for

Always receive this injection at a proper hospital or clinic, never from unqualified people or roadside medicine sellers. Complete the full course of treatment even if you feel better, as stopping early can make the infection come back stronger and harder to treat. Tell your doctor immediately if you develop any rash, itching, or difficulty breathing after the injection.

Common Side Effects

Pain or swelling at the injection site
diarrhoea
mild skin rash
nausea or vomiting
mild fever

Serious Side Effects

Severe allergic reaction (difficulty breathing, swelling of face or throat, widespread rash): this can be life-threatening
go to the hospital immediately. Seizures or convulsions
especially with very high doses. Severe watery or bloody diarrhoea that does not stop.

Drug Interactions

Methotrexate (used for arthritis and some cancers): benzylpenicillin can increase its harmful effects. Probenecid (used for gout) can increase the level of penicillin in your blood, which your doctor may sometimes use on purpose. Blood thinners like warfarin may have stronger effects when used alongside this drug.

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Pregnancy & Breastfeeding Warning

Benzylpenicillin is generally considered safe during pregnancy and breastfeeding, but always let your doctor know if you are pregnant or breastfeeding before receiving it.

Who Should NOT Take This

Anyone who has ever had an allergic reaction to penicillin or any other penicillin-type antibiotic (like amoxicillin or ampicillin) should NOT take this drug. People with a history of severe allergic reactions to other antibiotics called cephalosporins should also inform their doctor before use.

How to Store

Store the dry powder in a cool, dry place below 25°C, away from direct sunlight and humidity. Once mixed with water for injection, use it immediately or store in a refrigerator and use within 24 hours. Always keep out of reach of children.

For information only: not medical advice. Always talk to a doctor or pharmacist before changing your medication.