Penicillin G
Penicillin G (benzylpenicillin; potassium, sodium, benzathine, procaine salts)
Bicillin L-A (benzathine), Bicillin C-R (combination procaine + benzathine), Pfizerpen (potassium IV)
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Summary
Common uses
Syphilis (benzathine IM, all stages)0, Single-dose IM treatment of streptococcal pharyngitis (benzathine)0, Rheumatic fever secondary prophylaxis (benzathine IM monthly)0, Pneumococcal meningitis (high-dose IV potassium G, susceptible strains)0, Streptococcal endocarditis (IV)0
Pharmacy
Starting dose
Syphilis (primary/secondary/early latent): benzathine 2.4 million units IM × 1; neurosyphilis: aqueous crystalline G 18-24 million units/d IV continuous infusion or divided q4h × 10-14 days; strep pharyngitis: benzathine 1.2 million units IM × 1; rheumatic fever prophylaxis: benzathine 1.2 million units IM every 3-4 weeks
Preparations
Bicillin L-A 600,000; 1.2M; 2.4M U IM; aqueous crystalline (Pfizerpen) 5M, 20M U IV; procaine 600,000 U/mL IM
US FDA Max
Indication-specific
Pharmacology
Routes
IM (benzathine, procaine), IV (aqueous crystalline); NEVER IV for benzathine — fatal cardiopulmonary events reported
Onset
IV: minutes; IM benzathine: depot levels last weeks
Duration
IM benzathine: 3-4 weeks of detectable levels
Half-life
Aqueous crystalline ~30 minutes; benzathine effective ~3 weeks via depot release[1]
Bioavailability
Acid-labile; not effective orally (oral form available outside US as penicillin G salts but penicillin V is preferred for oral use)[1]
Pregnancy
Penicillin G is the only fully effective syphilis treatment in pregnancy; penicillin-allergic pregnant patients require desensitization.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Penicillin G binds penicillin-binding proteins (PBPs), inhibiting transpeptidation of peptidoglycan cross-links and producing osmotic lysis of growing organisms; it is the prototype β-lactam antibiotic.0 Narrow-spectrum: Group A and oral streptococci, Treponema pallidum, susceptible pneumococci, meningococci, some anaerobes. Benzathine and procaine salts produce IM depot release lasting weeks (benzathine) to days (procaine) — the basis of single-dose syphilis treatment[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Bicillin L-A (penicillin G benzathine), Pfizer, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/050719s016lbl.pdf