benzylpenicillin benzathine at a glance
Medicine class
Long-acting, beta-lactamase-sensitive penicillin antibiotic
Administration
Deep intramuscular injection by a healthcare professional; never intravenous
Usual role
Treatment of syphilis and selected skin or treponemal infections; prevention of certain streptococcal complications
Key safety check
Previous reactions to penicillins, cephalosporins or other beta-lactam antibiotics must be reviewed
What is benzylpenicillin benzathine used for?
Licensed uses represented by the selected product include:
Early syphilis, including primary and secondary disease
Latent syphilis, except when neurosyphilis or abnormal cerebrospinal-fluid findings are present
Erysipelas
Yaws and pinta
Prevention of rheumatic fever, post-streptococcal glomerulonephritis and recurrent erysipelas
How does benzylpenicillin benzathine work?
The depot formulation slowly releases benzylpenicillin after injection. Benzylpenicillin prevents susceptible bacteria from building stable cell walls. It is ineffective against penicillin-resistant organisms, including many beta-lactamase-producing bacteria.
How to take benzylpenicillin benzathine
A healthcare professional prepares the powder as a suspension and gives it by deep intramuscular injection. It must not be injected into a vein, artery, under the skin or into poorly perfused tissue. Lidocaine may sometimes be used as the diluent after suitability checks.
Tell the clinician about previous antibiotic or lidocaine reactions.
Remain for any observation requested after the injection.
Do not rub the injection site afterwards.
benzylpenicillin benzathine side effects
Common or expected effects
- Diarrhoea
- Nausea
- Candidiasis, such as thrush
- Changes in certain laboratory-test results
Get urgent medical advice
- Severe allergic reaction, including anaphylaxis or angioedema
- Severe antibiotic-associated colitis
- Seizures, confusion, altered consciousness or abnormal movements
- Serious blood-cell disorders
- Kidney inflammation or liver injury
- Severe neurovascular injury following injection into an incorrect site
benzylpenicillin benzathine in pregnancy
It crosses the placenta but can be used during pregnancy when clinically indicated after benefit–risk assessment. Penicillins have not raised concerns about harm to the baby, while untreated infection—particularly syphilis—can cause serious pregnancy and neonatal complications. Syphilis requires coordinated specialist, maternity and neonatal follow-up.
benzylpenicillin benzathine while breastfeeding
Penicillins can generally be used during breastfeeding after individual assessment; only small quantities are expected in milk. Monitor the infant for diarrhoea, thrush, rash, feeding problems or breathing symptoms. Specialist advice is appropriate if the infant is premature or unwell, or treatment is prolonged.
benzylpenicillin benzathine interactions
Tell the prescriber about all medicines being used, particularly:
Methotrexate
Penicillin may reduce methotrexate elimination and increase toxicity; concurrent use is not recommended by the product information.
Oral vitamin K antagonist anticoagulants
The anticoagulant effect and bleeding risk may increase, so closer INR monitoring may be required during and after treatment.
Probenecid
It reduces renal secretion of benzylpenicillin, increasing and prolonging blood concentrations.
Common questions about benzylpenicillin benzathine
Answers are fully visible for fast scanning and source review.
Why is it given into a muscle?
The benzathine formulation forms a depot in muscle, allowing benzylpenicillin to be released and absorbed slowly. It is not formulated for intravenous administration.
Is it the same as benzylpenicillin sodium?
No. Benzylpenicillin benzathine is a long-acting intramuscular depot formulation; benzylpenicillin sodium is short acting and may be given by different routes. Confusing the salts can cause serious harm.
Can it treat neurosyphilis?
No. It does not achieve adequate concentrations in the central nervous system and is unsuitable when neurosyphilis or abnormal cerebrospinal-fluid findings are present.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.