[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) › Procaine benzylpenicillin [Pharmacology](https://durgical.com/en/pharmacology/) · [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) # Procaine benzylpenicillin A procaine salt of penicillin G for intramuscular injection, shorter-acting than the benzathine salt; it can cause a brief neuropsychiatric reaction. Updated 2026-11-01 - Class: [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) - Enzyme: Penicillin-binding proteins (bacterial DD-transpeptidases) - ATC code: J01CE09 - WHO Model List of Essential Medicines Also called: penicillin G procaine, procaine penicillin ✂**Penicillin-binding proteins (bacterial DD-transpeptidases)**Procaine benzylpenicillin ⓘ The figure shows the DD-peptidase of Streptomyces R61, the classic PBP model, acylated by penicillin G (the active molecule the procaine salt releases). **Target in 3D:** Penicillin-binding proteins (bacterial DD-transpeptidases). PDB structure 1PWC (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1PWC) · Drag to rotate · pinch to zoom ## Mechanism of action The procaine salt of penicillin G forms an intramuscular depot that releases penicillin G over hours, longer than soluble penicillin G but much shorter than the benzathine salt. Penicillin G acylates the PBPs of streptococci, Treponema and other susceptible organisms. The released procaine can cause an immediate brief reaction of anxiety, confusion or hallucinations. - The intramuscular injection forms a depot - The depot releases penicillin G over hours - Penicillin G acylates the PBPs - Dividing bacteria lyse ## Pharmacokinetics **Absorption** Slow from muscle; useful levels for hours after each injection. **Elimination** The released penicillin is cleared by the kidney. ## Indications - Mild to moderate infections by susceptible streptococci, such as pharyngitis. [Streptococcal pharyngitis →](https://durgical.com/en/conditions/streptococcal-pharyngitis/) - Some forms of syphilis, depending on the stage and guidelines. [Syphilis →](https://durgical.com/en/conditions/syphilis/) ## Adverse effects ### Common - Pain, lump or bruising at the injection site - Immediate procaine reaction: anxiety, agitation, confusion, hallucinations or seizures, lasting minutes ### Serious (rare, important) - Anaphylaxis - Nerve or vessel injury from injection in the wrong place - Clostridioides difficile diarrhoea, from mild to severe colitis ## Contraindications - Allergy to penicillin or to procaine - It is not a treatment for gonorrhoea ## Key interactions **Probenecid** Reduces tubular secretion: higher and longer-lasting β-lactam levels. **Tetracyclines and chloramphenicol** Bacteriostatic drugs can antagonise the bactericidal effect. ## What is monitored - Observe the patient after each injection - In syphilis, serological response ## Administration and safety - Deep intramuscular only, in the buttock or thigh; never intravenous. - Do not confuse with benzathine benzylpenicillin or the mixture of both: duration and uses differ. - Aspirate before injecting. ## Nursing care - Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was. - Also ask about allergy to procaine or other local anaesthetics. - Keep the patient under observation: if the procaine reaction occurs, reassure, protect from injury and report. - After the first dose, watch for hives, wheeze, low blood pressure or swelling of lips and tongue, with anaphylaxis equipment at hand. ## Pregnancy and breastfeeding Penicillins are widely used in pregnancy without a known rise in birth defects. ## Memory aid 'Procaine = passing panic': minutes of fear or confusion after the injection, without being allergy; it lasts hours, not weeks like benzathine. ## Test yourself Think of the answer, then tap the question to see it. ## What is the immediate reaction that can follow a procaine penicillin G injection? A brief neuropsychiatric reaction to procaine (anxiety, confusion, hallucinations) that lasts minutes and is not a penicillin allergy. ## How does it differ from benzathine benzylpenicillin? It releases penicillin over hours, not weeks, and reaches higher levels; the benzathine salt is the longest-acting. ## Is procaine penicillin used for gonorrhoea today? No: many gonococcal strains are resistant to penicillin. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/procaine-benzylpenicillin/) ## Related drugs - [Benzathine benzylpenicillin](https://durgical.com/en/pharmacology/benzathine-benzylpenicillin/) - [Benzylpenicillin (penicillin G)](https://durgical.com/en/pharmacology/benzylpenicillin/) ## Related conditions - [Streptococcal pharyngitis](https://durgical.com/en/conditions/streptococcal-pharyngitis/) - [Syphilis](https://durgical.com/en/conditions/syphilis/) [← Back to the class: Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Penicillin G Procaine Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a615052.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [Syphilis - STI Treatment Guidelines](https://www.cdc.gov/std/treatment-guidelines/syphilis.htm) (Centers for Disease Control and Prevention (CDC), 2021); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/procaine-benzylpenicillin/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/procaine-benzylpenicillin/