Comparative Pharmacology
Head-to-head clinical analysis: PENICILLIN G PROCAINE versus PENICILLIN 2.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PENICILLIN G PROCAINE versus PENICILLIN 2.
PENICILLIN G PROCAINE vs PENICILLIN-2
Head-to-head clinical comparison of therapeutic indices and safety profiles.
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation, and activating autolytic enzymes.
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and activating autolytic enzymes.
Moderate to severe infections caused by penicillin G-sensitive microorganisms (FDA)Syphilis (treponemal infections)Anthrax (post-exposure prophylaxis)Group A streptococcal infectionsPneumococcal infectionsEndocarditis (certain strains)Lyme disease (off-label)Leptospirosis (off-label)
Streptococcal infectionsPneumococcal infectionsMeningococcal infectionsSyphilisLyme diseaseAnthraxActinomycosisProphylaxis for rheumatic fever
1.2 million to 2.4 million units intramuscularly once daily for most infections (e.g., uncomplicated pneumonia); for neurosyphilis, 2.4 million units intramuscularly once daily plus probenecid 500 mg orally four times daily for 10-14 days. Administer deep IM injection, not IV.
250 mg orally every 6 hours or 500 mg orally every 8 hours for mild to moderate infections; intravenous dosing: 1-2 million units every 4-6 hours.
None Documented
None Documented
Terminal elimination half-life is approximately 0.5-1 hour in patients with normal renal function. Clinically, the prolonged absorption from the intramuscular depot results in sustained serum concentrations, with effective levels lasting 12-24 hours.
30-60 minutes; prolonged in renal impairment (up to 10 hours in anuria)
Hepatic hydrolysis to penicillin G (active) and p-aminobenzoic acid; penicillin G is primarily renally excreted unchanged (60-90%).
Primarily eliminated unchanged by renal tubular secretion; minor hepatic metabolism to penicilloic acid.
Primarily renal excretion via tubular secretion and glomerular filtration. Approximately 60-90% of a dose is excreted unchanged in urine within 24 hours. Biliary/fecal elimination is minor (<10%).
Renal: 60-80% unchanged; biliary/fecal: minor (10-20%)
Approximately 60% bound to serum proteins, primarily albumin.
50-65% bound, primarily to albumin
Volume of distribution is approximately 0.3-0.4 L/kg, indicating distribution primarily into extracellular fluid.
0.3-0.5 L/kg; low Vd indicates limited tissue penetration
Intramuscular: Bioavailability is approximately 100% (complete absorption). No oral bioavailability due to acid lability.
Oral: 60-70% (decreased with food); IM: 70-85%
Creatinine clearance (CrCl) 10-50 mL/min: reduce dose to 50% of normal or extend interval to every 12-24 hours. CrCl <10 mL/min: 25% of normal dose or every 24-48 hours. For severe infections, monitor serum levels.
For CrCl 10-50 mL/min: administer every 8-12 hours; for CrCl <10 mL/min: administer every 12-18 hours; hemodialysis: give after dialysis.
No dosage adjustment is routinely recommended for Child-Pugh Class A, B, or C; penicillin G procaine is primarily renally eliminated. Use with caution in severe hepatic impairment due to potential for coagulopathy.
No specific Child-Pugh based dose adjustment; use with caution in severe hepatic impairment.
Children: 25,000-50,000 units/kg intramuscularly once daily (maximum 2.4 million units/day). For congenital syphilis, 50,000 units/kg intramuscularly once daily for 10-14 days. Not recommended in neonates due to high risk of procaine toxicity.
For children >1 month: 25-50 mg/kg/day orally divided every 6-8 hours; severe infections: 100-250 mg/kg/day IV divided every 4-6 hours; maximum 12 g/day.
Start at the lower end of dosing range due to age-related renal function decline. Assess CrCl and adjust dose according to renal adjustment guidelines. Monitor for neurologic adverse effects (procaine toxicity) and ensure adequate hydration.
No specific dose adjustment except for renal function; monitor renal function and adjust dose accordingly.
No FDA black box warning.
No FDA black box warning.
["Severe hypersensitivity reactions (anaphylaxis) can occur; monitor for 30 minutes after injection.","Procaine toxicity (CNS stimulation, seizures) with inadvertent intravascular injection.","Use with caution in renal impairment (dosage adjustment required).","Pseudomembranous colitis due to Clostridium difficile overgrowth.","Jarisch-Herxheimer reaction in syphilis treatment."]
["Hypersensitivity reactions including anaphylaxis","Severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome)","Clostridioides difficile-associated diarrhea","Renal impairment requiring dose adjustment","Neurologic toxicity with high doses (seizures)"]
["Hypersensitivity to penicillins","Hypersensitivity to procaine","Neonates (due to procaine toxicity risk)"]
["Hypersensitivity to penicillins","History of severe immediate hypersensitivity reaction to beta-lactam antibiotics"]
Data Pending Review
Data Pending Review
No significant food interactions. However, avoid alcohol as it may increase side effects like dizziness or gastrointestinal upset.
No significant food interactions. Can be taken with or without food.
Penicillin G procaine is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate well-controlled studies in pregnant women. However, because animal reproduction studies are not always predictive of human response, it should be used during pregnancy only if clearly needed. There is no evidence of teratogenicity in humans, but theoretical risk of allergic reaction exists. No specific fetal risks have been identified in any trimester.
Penicillin is generally considered low risk; no significant teratogenic effects have been consistently reported in first trimester. Animal studies show no fetal harm. Use is considered safe across all trimesters when indicated.
Penicillin G is excreted into breast milk in low concentrations. The milk-to-plasma (M/P) ratio is approximately 0.2. Although unlikely to be harmful to the nursing infant, it may cause alteration of gut flora, diarrhea, or allergic sensitization. Use with caution in breastfeeding women.
Penicillin is excreted into breast milk in low concentrations (M/P ratio approximately 0.2). It is compatible with breastfeeding; no adverse effects on nursing infants reported. Caution in infants with history of penicillin allergy.
Physiologic changes during pregnancy (increased plasma volume, increased renal clearance) may lower serum penicillin concentrations. However, no specific dose adjustments are recommended for penicillin G procaine. Standard dosing regimens are considered adequate. Monitor clinical response and consider dose adjustment if infection is severe or if patient is near term.
Increased renal clearance in pregnancy may reduce serum concentrations; higher doses may be required for severe infections, but standard dosing is generally adequate. No specific dose adjustment is uniformly recommended; monitor clinical response.
Category A/B
Category C
Penicillin G procaine is a long-acting intramuscular formulation used primarily for syphilis and other susceptible infections. Due to procaine component, it is contraindicated in patients with procaine allergy. Always confirm lack of allergy to both penicillin and procaine. Administer deep IM in the gluteal region; avoid intravascular injection to prevent procaine toxicity or Jarisch-Herxheimer reaction. Monitor for procaine reactions (e.g., anxiety, confusion, seizures) particularly in elderly or those with renal impairment. Not for IV use.
Penicillin-2 (benzathine penicillin G) is indicated for syphilis and group A streptococcal infections. Intramuscular injection only; avoid intravenous administration. Monitor for Jarisch-Herxheimer reaction. Dose adjustment in renal impairment is not typically required due to slow release.
This medication is given as an injection into your muscle, usually in the buttock.You may experience pain, swelling, or redness at the injection site.Report any signs of allergic reaction such as rash, itching, swelling, or difficulty breathing immediately.You might develop a reaction called Jarisch-Herxheimer reaction (fever, chills, muscle aches) within 24 hours, especially if being treated for syphilis; this is not an allergic reaction but notify your doctor.Avoid driving or operating machinery if you feel dizzy or anxious after the injection.Complete the full course of injections even if you feel better.
Complete the full course as prescribed, even if symptoms improve.Report any rash, difficulty breathing, or swelling immediately.Avoid alcohol during treatment to minimize side effects.Do not stop or change the dose without consulting your doctor.Inform all healthcare providers about this therapy.