Drug Index

Benzyl Penicillin

Synonym :

Penicillin G

Mechanism :

It is also known as Penicillin G; Penicillin G exerts a bactericidal action against penicillin-susceptible microorganisms during the stage of active multiplication. It acts through the inhibition of biosynthesis of cell-wall mucopeptide. It is not active against the penicillinase-producing bacteria, which include many strains of staphylococci.

Indication :

  • Streptococcal throat infections e.g., pharyngitis.
  • Cellulitis
  • Impetigo
  • Erysipelas
  • Septic Arthritis
  • Osteomyelitis
  • Endocarditis
  • Anthrax
  • Congenital syphilis
  • Leptospirosis

Contraindications :

A history of a previous hypersensitivity reaction to any of the penicillin’s is a contraindication.

Dosing :


Mild infection: 50,000 units/kg/dose 8 hourly for 7-10 days.

Moderate infection: 50,000 units/kg/dose 6 hourly for 10-14 days.

Severe infection like endocarditis: 50,000 units/kg/dose 4 hourly for 10-14 days. Max: 24 million units/day.

Congenital Syphilis:

<7 days: 50,000 units/kg/dose IV every 12 hours for 7 days and then every 8 hours for next 3 days.

>7 days: 50,000 units/kg/dose IV every 8 hours for 10 days.


Neonates: 50,000 units/kg/dose every 6 hours for 2 weeks.

>1 month of age: 100,000 units/kg/dose every 6 hours for 2 weeks.

Adverse Effect :

Maculopapular eruptions, exfoliative dermatitis, urticaria, Jarisch-Herxheimer reaction, anaphylaxis, laryngeal edema, serum-sickness like reactions (chills, fever, edema, arthralgia, prostration, eosinophilia), hemolytic anemia, leukopenia, thrombocytopenia.

Interaction :

Tetracycline: May antagonize the bactericidal effect of penicillin, and concurrent use of these drugs should be avoided.
Probenecid: Prolongs serum penicillin levels by slowing the rate of excretion by competitively inhibiting renal tubular secretion of penicillin.

Renal Dose :

Dose in Renal Impairment GFR (mL/min)
20-50Dose as in normal renal function
10-20600 mg – 2.4 g every 6 hours depending on severity of infection
<10600 mg – 1.2 g every 6 hours depending on severity of infection

Dose in Patients undergoing Renal Replacement Therapies
CAPDDialysed. Dose as in GFR<10 mL/min
HDDialysed. Dose as in GFR<10 mL/min
HDF/High fluxDialysed. Dose as in GFR<10 mL/min
CAV/VVHDDialysed. Dose as in GFR=10–20 mL/min

Hepatic Dose :

In patients with altered renal function, the presence of hepatic insufficiency further alters the elimination of benzyl penicillin. The dosage of penicillin G should be reduced in patients with severe renal impairment, with additional modifications when hepatic disease accompanies the renal impairment.
01/24/2024 03:26:16 Benzyl Penicillin
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