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Indications

Benzathine Penicillin (Benzathine Benzylpenicillin) is a long acting penicillin injection. It is used to prevent rheumatic fever from coming back in people who have had it, to treat syphilis and other treponemal infections such as yaws, and to treat sore throat caused by Group A streptococcus bacteria.

How It Works

After injection into a muscle, the medicine forms a small store that slowly releases Penicillin into the blood over 2 to 4 weeks. Penicillin stops sensitive bacteria from building their cell wall, so they break apart and die. The slow release means a single injection can protect or treat for a long time.

Dosage and Administration

It is given only by a doctor or nurse as a deep injection into a large muscle, usually the buttock or thigh. It must never be injected into a vein. The dose and schedule (for example a single dose, or a dose every 3 to 4 weeks to prevent rheumatic fever) are set by the doctor. Keep to the injection dates exactly when it is used for prevention.

Interactions

• Probenecid increases and prolongs Penicillin levels.
• Tetracyclines and some other antibiotics that stop bacteria growing may reduce its effect.
• It may increase the effect of Methotrexate.
• Tell the health worker about all medicines you take.

Contraindications

• Allergy to any penicillin.
• People with a past serious allergic reaction to cephalosporins or other beta lactam antibiotics should tell the doctor; it is usually avoided.

Side Effects

Pain, tenderness and a lump at the injection site are common. Others include rash, fever, and, when treating syphilis, a short reaction in the first day with fever, chills, headache and muscle aches (Jarisch Herxheimer reaction).

Get urgent medical help, and stay at the clinic for at least 30 minutes after the injection, because rare severe allergic reactions (anaphylaxis) can occur: watch for swelling of the face or throat, trouble breathing, wheezing, faintness, widespread rash or hives. Also seek help for severe pain, numbness or colour change in the injected leg.

Pregnancy and Lactation

Penicillin is considered safe in pregnancy and is the preferred treatment for syphilis in pregnancy to protect the baby. Small amounts pass into breast milk; breastfeeding can usually continue.

Precautions and Warnings

• Always tell the health worker about any past drug allergy before the injection.
• It should be given only where emergency treatment for allergy is available.
• Use with care in kidney disease, asthma and other allergic conditions.

Overdose

Overdose is unlikely as it is given by health workers. Very high doses can rarely cause fits, especially in kidney disease. Supportive medical care is given.

Therapeutic Class

Long acting penicillin antibiotic (beta lactam).

Storage

Store below 25°C as directed on the pack, in a dry place away from light and out of the reach of children. Use the mixed suspension immediately.