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Generic Name: Benzylpenicillin sodium
Product Name: BenPen


Used in the treatment of infections caused by pathogens sensitive to benzylpenicillin, including syphilis.Used as prophylactic treatment in patients undergoing procedures at risk of developing bacterial endocarditis, wound infections and sepsis caused by Streptococci.



  • Benzylpenicillin exerts bactericidal activity against some micro-organisms responsible for common and serious infections, including bacterial meningitis and syphilis.


  • Effective concentrations last for 4-6 hours.
  • In the presence of normal renal function, 70% of the dose is excreted within 6 hours. 30% is inactivated by the liver and 4.5% is excreted in the bile.
  • Serum half life increases as renal function deteriorates, and patients with poor renal tubular secretory ability are at risk of neurotoxicity in the presence of large intravenous doses.

Dose advice

Dosage level and frequency of administration should be guided by the nature & severity of the infection, and the status of the patient.

Adults, Children > 10 years old

Minimum dose:

  • 300 mg, 6 hourly.
  • Dosage and frequency of administration may be increased in the cases of severe infections or more resistant organisms. 4-24 g may need to be given daily in severe infections.

Infants, Children < 10 years old

  • Premature babies and neonates: 30-60 mg, 12 hourly.
  • Children < 3 years: 60 mg, 6 hourly.
  • Children 3-10 years: 150-300 mg, 6 hourly.Dosage and frequency of administration may be increased in the cases of severe infections or more resistant organisms.

Meningococcal meningitis:

  • First dose 600 mg intramuscularly, then 300 mg intramuscularly, every 4-6 hours.

Pneumococcal meningitis:

  • 300 mg, every 4 hours, for 14 days. Then, 300 mg, every 6 hours, for 7 days.

Elderly patients

  • Penicillin elimination is often reduced. Blood levels should be monitored if high doses are used.

Renal Impairment:

  • Patients with severe renal failure should tolerated doses up to 6 g daily, though intravenous doses > 20 g daily may precipitate convulsions and coma.
  • Intramuscular and intravenous maintenance doses can be calculated as follows:
    • Maintenance dose (g/24 hours) = benzylpenicillin clearance (mL/min) x desired serum benzylpenicillin concentration (microgram/mL) x 0.00138.(Benzylpenicillin clearance (mL/min) = 35.5 + 3.35 x creatinine clearance (mL/min)Subacute bacterial endocarditis. 1.2 g daily, in divided doses, four 4-6 weeks. Doses of up to 24 mg daily may be required for relatively resistant organisms.

Surgical Prophylaxis:

  • 600 mg intravenously, prior to surgery. Further doses of 600 mg may be given every 4-8 hours during prolonged procedures.

Clostridial infections:

  • In addition to standard surgical procedures, 1.2 g intravenously, every 6 hours, for 48 hours.

Use in pregnancy

  • Category A. BenPen crosses the placenta, though studies have not shown teratogenic effects.
  • Its use in pregnancy is at the discretion of the clinician, and should only be used in cases considered essential.

Use in lactation:

  • Breastfeeding women should use an alternative feeding method if taking BenPen.



Common side effects

In the treatment of syphilis or leptospirosis:

Uncommon side effects

For further information talk to your doctor.

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Posted On: 22 July, 2003
Modified On: 7 June, 2006

Created by: myVMC