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 :
IV/IM
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.
Anthrax:
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)
| 20-50 | Dose as in normal renal function |
| 10-20 | 600 mg – 2.4 g every 6 hours depending on severity of infection |
| <10 | 600 mg – 1.2 g every 6 hours depending on severity of infection |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Dialysed. Dose as in GFR<10 mL/min |
| HD | Dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Dialysed. Dose as in GFR<10 mL/min |
| CAV/VVHD | Dialysed. 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.