Benzathine benzylpenicillin

Benzathine benzylpenicillin, also known as benzathine penicillin G (BPG), is an antibiotic medication useful for the treatment of a number of bacterial infections. Specifically it is used to treat strep throat, diphtheria, syphilis, and yaws. It is also used to prevent rheumatic fever. It is given by injection into a muscle. It is known as "Peanut Butter Shot" in US military slang due to its appearance.

Side effects include allergic reactions including anaphylaxis, and pain at the site of injection. When used to treat syphilis a reaction known as Jarisch-Herxheimer may occur. It is not recommended in those with a history of penicillin allergy or those with syphilis involving the nervous system. Use during pregnancy is generally safe. It is in the penicillin and beta lactam class of medications and works via benzylpenicillin. The benzathine component slowly releases the penicillin making the combination long acting.

Benzathine benzylpenicillin was patented in 1950. It is on the World Health Organization's List of Essential Medicines.

Medical uses
It is used to treat strep throat, diphtheria, syphilis, and yaws.

Chemopreventive
A single large 1.2-million-unit dose of intramuscular BPG is given to US military recruits. The Army in particular has a policy to inject all recruits if not allergic, though supply issues and individual base choices have reduced the coverage. A retrospective analysis shows that it reduces the rate of all-cause acute respiratory disease by 32% among Army recruits.

Adverse effects


The possible adverse effects are generally similar to other forms of penicillin. BPG is overall well-tolerated, but pain from the injection site is a common concern.

Mechanism of action
It is in the penicillin class of medications. It is slowly absorbed into the circulation, after intramuscular injection, and hydrolysed to benzylpenicillin in vivo. It is the drug-of-choice when prolonged low concentrations of benzylpenicillin are required and appropriate, allowing prolonged antibiotic action over 2–4 weeks after a single IM dose.

Society and culture
It is marketed by Pfizer (formerly by Wyeth) under the trade name Bicillin L-A.

Compendial status

 * British Pharmacopoeia