BENZATHINEPENICILLIN INJECTION BP 5 MEGA
BENZATHINEPENICILLIN SODIUM BP
What it does
Benzathine penicillin is an antibiotic used to treat bacterial infections.
Commonly used for: rheumatic fever, syphilis, throat infections (like strep throat)
Read more in plain English ↓Plain-language summary for general understanding - not medical advice. Always follow your pharmacist/doctor.
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Source: Pharmacy and Poisons Board · fetched 2026-01-28 21:09:29 · updated 2026-07-26 13:51:55
About this medicine
Benzathine penicillin is an antibiotic used to treat bacterial infections.
What it treats
- rheumatic fever
- syphilis
- throat infections (like strep throat)
How it works
It works by killing bacteria or stopping their growth, helping to clear up infections.
Who it's for
It is usually prescribed for people with certain bacterial infections, especially those at risk of rheumatic fever or with syphilis.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: benzathinepenicillin
Benzathine penicillin is a long-acting form of penicillin used primarily to treat infections caused by susceptible organisms. It is particularly effective against streptococcal infections, including rheumatic fever prophylaxis, and is also used in the treatment of syphilis. This antibiotic is administered intramuscularly due to its slow release and prolonged action in the body.
Indications
- Rheumatic fever prophylaxis
- Streptococcal pharyngitis
- Syphilis treatment
- Prevention of infections in patients with rheumatic heart disease
- Treatment of certain skin and soft tissue infections
Dosage
Children: Refer to the BNF for Children for specific dosing recommendations for paediatric patients.
Adults: Refer to the BNF for specific dosing recommendations for adults.
Mechanism of action
Benzathine penicillin works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) located inside the bacterial cell wall, disrupting the transpeptidation process, which is essential for the cross-linking of peptidoglycan layers. This leads to cell lysis and ultimately the death of the bacteria.
Pharmacodynamics
Benzathine penicillin exhibits time-dependent bactericidal activity against gram-positive bacteria and certain gram-negative bacteria. Its prolonged half-life allows for sustained therapeutic levels in the body, making it effective for the prevention of infections over an extended period. The drug is particularly potent against Streptococcus pyogenes and is also active against some strains of Staphylococcus aureus.
Pharmacokinetics
After intramuscular injection, benzathine penicillin is slowly absorbed into the bloodstream, leading to peak serum concentrations occurring several hours after administration. The drug is distributed widely in body tissues, and its half-life can extend for several days due to its depot formulation. It is primarily eliminated by the kidneys, with a small amount excreted in urine as unchanged drug.
Contra-indications
- Hypersensitivity to benzathine penicillin or any component of the formulation
- History of severe allergic reactions to penicillins or other beta-lactam antibiotics
Adverse effects
- Allergic reactions, including anaphylaxis
- Rash
- Fever
- Nausea
- Diarrhea
- Injection site reactions, including pain and swelling
Interactions
- Other antibiotics may alter the effectiveness of benzathine penicillin
- Probenecid may increase the plasma concentration of penicillins
- Anticoagulants may have altered effects when used concurrently
Precautions
- Use with caution in patients with a history of asthma or allergic conditions
- Monitor for signs of superinfection during prolonged use
- Ensure proper administration technique to avoid complications
Pregnancy
Benzathine penicillin is generally considered safe for use during pregnancy, but should only be used if clearly needed.
Breast-feeding
Benzathine penicillin is excreted in breast milk in small amounts and is considered safe for use during breastfeeding.
Storage
Store at room temperature, away from light and moisture. Do not freeze.
Formulations
- Benzathine penicillin G injection
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.