pcn

Penicillin G (PCN G) Overview

• Category: Narrow-spectrum penicillin
• Primary Function: Active against gram-positive bacteria, gram-negative cocci, anaerobes, & spirochetes; first-line treatment for sensitive gram-positive cocci infections.
• Unique Feature: First penicillin available; remains a preferred choice for many infections.
• Mechanism of Action: Weakens bacterial cell walls, causing rupture due to overhydration. Achieved by inhibiting transpeptidases and disinhibiting autolysins, leading to lysis & death. Only effective during bacterial growth & division.

Indications & Therapeutic Uses

• Gram-Positive Cocci: First-choice for infections like Streptococcus pneumoniae (pneumonia), Streptococcus pyogenes (pharyngitis), and Streptococcus viridans (infectious endocarditis).
• Gram-Positive Bacilli: Preferred for gas gangrene, tetanus, and anthrax.
• Meningitis: Treatment for Neisseria meningitidis meningitis.
• Gonorrhea: Treatment for non-penicillinase-producing strains of Neisseria gonorrhoeae; replaced by ceftriaxone for most gonorrhea cases.
• Syphilis: First-line treatment for Treponema pallidum; prophylaxis for exposed partners.
• Rheumatic Fever: Prevention/treatment of recurrent rheumatic fever.
• Bacterial Endocarditis: Prophylaxis for prosthetic heart valves, congenital heart disease, acquired valvular heart disease, mitral valve prolapse, & history of bacterial endocarditis.

Side Effects & Adverse Reactions

• Hypersensitivity: Most concerning; potentially life-threatening allergic reaction.
• Injection Site Reactions: Pain, gangrene (arterial injection), nerve damage (peripheral nerve injection).
• Neurotoxicity: Seizures, confusion, hallucinations with high toxicity.

Precautions & Contraindications

• Penicillin Allergy: Consider all penicillin agents as contraindications.
• Cephalosporin Cross-Sensitivity: Avoid cephalosporins in patients with severe, immediate penicillin allergies due to possible cross-reactivity.
• Sodium Restriction: Use sodium penicillin G cautiously in sodium-restricted diets.

Drug Interactions

• Bacteriostatic Agents: Concurrent use (e.g., tetracyclines) can reduce penicillin's bactericidal effects. Avoid concurrent use.

Dosing, Administration, & Client Teaching

• Dosing: Varies; consult guidelines for individualized dosing based on condition, severity, and response. Available as potassium PCN G, procaine PCN G, benzathine PCN G, & sodium PCN G. Intramuscular (IM) and intravenous (IV) administration.
• Administration: IM or IV, closely monitor for hypersensitivity.
• Client Education: Emphasize completing the full course. Educate clients about side effects, monitoring, and reporting concerns.

Monitoring Labs

• Basic Metabolic Panel (BMP): Monitor renal function (BUN/Creatinine, Creatinine Clearance), as renal impairment significantly increases penicillin half-life, requiring dose adjustments.