Penicillin G

C. diff Risk


Oral Bioavailability


Approximate Cost



20- 24 million units q24h (24-hr infusion)

Latent or secondary Syphilis
2.4 million units IM weekly x 3 injections

General Information

Common Usage

Therapy of Streptococcal and other documented susceptible infections, syphilis

Drug Monitoring


  • CBC, CMP weekly

Adverse Effects

  • Allergy/rash (immediate or delayed)

  • Seizures

  • Cytopenias

  • Eosinophilia

  • Interstitial nephritis

  • Abnormal liver enzymes

  • Serum sickness

Additional Information

A large number of patients who are listed as penicillin-allergic will test negative for penicillin allergy on skin testing. Consult ID or Allergy/Immunology


Antimicrobial class: Penicillin

Pregnancy category: B

Average serum half life: 1 hour

Biliary penetration: Therapeutic

CSF penetration: Moderate

Lung penetration: Therapeutic

Urine penetration: Therapeutic