Penicillin

The world’s first antibiotic, used to treat many bacterial infections.

What is Penicillin?

Penicillin is a beta-lactam antibiotic that kills bacteria by interfering with their cell wall formation.

It laid the foundation for modern antibiotic therapy.

History & Background

Penicillin was discovered in 1928 by Alexander Fleming. It revolutionized medicine and dramatically reduced deaths from infections.

Chemical Structure & Properties

• Core structure: Beta-lactam ring
• General formula: C₉H₁₁N₂O₄S (Penicillin G)
• Molar mass: ~334.4 g/mol
• Functional groups: Beta-lactam, thiazolidine ring

Mechanism of Action

Penicillin works by:

• Inhibiting bacterial cell wall synthesis
• Binding to penicillin-binding proteins (PBPs)
• Causing bacterial cell death (bactericidal)

Pharmacokinetics

• Absorption: Poor oral absorption (Penicillin G)
• Administration: Oral or injectable (varies by type)
• Half-life: 30–60 minutes
• Excretion: Urine

Medical Uses

• Streptococcal infections
• Syphilis
• Skin and soft tissue infections
• Respiratory tract infections

Dosage Guidelines

Adults: Dose varies by type and infection

Route: Oral or intramuscular/intravenous

⚠️ Must be taken exactly as prescribed.

Side Effects

• Nausea
• Diarrhea
• Skin rash
• Allergic reactions

Warnings & Precautions

• Penicillin allergy can be life-threatening
• Avoid use without medical advice
• Complete full antibiotic course

Drug Interactions

• Methotrexate
• Oral contraceptives
• Probenecid

Frequently Asked Questions

Is penicillin still used? – Yes.

Is it effective against viruses? – No.

Is penicillin safe? – Yes, unless allergic.

Why is allergy common? – Immune hypersensitivity.

⚠️ Educational content only. Not a substitute for professional medical advice.