Indications
Benzathine Penicillin G is a long-acting penicillin antibiotic given by deep injection into a muscle. It is used for infections caused by bacteria that are sensitive to low but steady levels of penicillin, including streptococcal sore throat (strep throat), syphilis and yaws. It is also given regularly to prevent rheumatic fever from coming back in people who have had it, which protects the heart valves. In animal health it is also found in combination injections with other penicillins and Dihydrostreptomycin for livestock.
How It Works
Penicillin stops bacteria from building their cell walls, so the bacteria burst and die. Benzathine Penicillin G dissolves very slowly from the injection site, releasing small amounts of penicillin into the blood over 2 to 4 weeks. This long action means one injection can treat some infections, and repeated injections can give ongoing protection.
Dosage and Administration
Given only by a doctor or nurse as a deep intramuscular injection, usually into the buttock or thigh muscle. It must never be injected into a vein. The dose and schedule are set by the doctor according to the infection, age and weight: for example a single injection for strep throat, one or more weekly injections for syphilis, or an injection every 3 to 4 weeks to prevent rheumatic fever. Keep every appointment for repeat injections. You will usually be asked to wait for about 30 minutes after the injection in case of an allergic reaction.
Interactions
- Probenecid raises and prolongs penicillin levels.
- Tetracyclines, Chloramphenicol and Erythromycin may reduce the effect of penicillin.
- Penicillin may increase the effect of Methotrexate and may affect blood tests for Warfarin control.
Contraindications
- Allergy to any penicillin. People allergic to Cephalosporins should tell the doctor, as cross-allergy can occur.
- Must not be given into a vein or artery.
Side Effects
Common effects are pain, swelling or a hard lump where the injection was given, mild rash, nausea and diarrhoea. When used for syphilis, a short-lived reaction with fever, chills, headache and muscle aches may occur within a day (Jarisch-Herxheimer reaction).
Rarely, serious allergic reactions (anaphylaxis) occur, and accidental injection into a blood vessel can damage tissue or nerves.
Get urgent medical help if you have difficulty breathing, wheezing, swelling of the face, lips or throat, a widespread itchy rash or hives, fainting, severe pain, coldness or colour change in the injected limb, or severe watery or bloody diarrhoea.
Pregnancy and Lactation
Benzathine Penicillin G is considered safe in pregnancy and is the treatment of choice for syphilis in pregnancy, which protects the baby. Small amounts pass into breast milk; breastfeeding can usually continue, but watch the baby for diarrhoea, thrush or rash.
Precautions and Warnings
- Always tell the doctor about any past reaction to penicillin or other antibiotics.
- Use with care in people with asthma or many allergies, and in severe kidney disease.
- It does not treat viral infections such as colds or flu.
- Missing preventive injections for rheumatic fever increases the risk of heart damage.
Overdose
Overdose is unlikely because it is given by a health professional. Very high levels may cause nerve irritation or seizures, especially in kidney failure. Treatment is supportive in hospital.
Therapeutic Class
Antibiotic, long-acting penicillin (beta-lactam).
Storage
Store as directed on the pack, usually below 25°C (some products 2 to 8°C, do not freeze), away from light, out of the reach of children. Use the mixed suspension immediately.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.