VitalsCentral

Amoxicillin

Amoxil | Trimox | Moxatag

FDA ApprovedAnti-InfectivesPenicillins
FDA: 1974Half-life: 1-1.5 hours (normal renal function)Pregnancy: Category B

Overview

Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), preventing cross-linking of peptidoglycan chains essential for cell wall strength.

Indications

  • Upper and lower respiratory tract infections
  • Otitis media
  • Urinary tract infections
  • Skin and soft tissue infections
  • H. pylori eradication (combination)
  • Dental infections

Contraindications

  • History of serious hypersensitivity reaction to any penicillin
  • History of cholestatic jaundice with amoxicillin

Classification

Anti-InfectivesPenicillinsImmune System

Mechanism of Action

Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), preventing cross-linking of peptidoglycan chains essential for cell wall strength.

Pharmacodynamics

Bactericidal, time-dependent killing. Broad-spectrum activity against gram-positive and some gram-negative bacteria.

Pharmacokinetics

Absorption
Rapid and nearly complete oral absorption. Not affected by food.
Distribution
Widely distributed to most tissues and fluids. Crosses placenta. Low CSF penetration (unless meninges inflamed).
Metabolism
Minimal hepatic metabolism (10%).
Excretion
Renal (60% unchanged in urine within 6-8 hours).
Half-life
1-1.5 hours (normal renal function)
Bioavailability
74-92%
Protein Binding
20%

Dosage

Typical dosage: 250-500mg every 8 hours, or 500-875mg every 12 hours

Available Forms

  • Capsule
  • Tablet
  • Chewable tablet
  • Oral suspension
  • Extended-release tablet

Side Effects

Common

  • Diarrhea
  • Nausea
  • Skin rash
  • Vomiting

Serious

  • Anaphylaxis
  • C. difficile-associated diarrhea
  • Seizures (high doses/renal impairment)

Rare

  • Stevens-Johnson syndrome
  • Hepatic cholestasis
  • Crystalluria

Drug Interactions

major

Amoxicillin may reduce renal clearance of methotrexate, increasing toxicity risk. Monitor methotrexate levels.

moderate

Amoxicillin may enhance anticoagulant effect by altering gut flora that produce vitamin K. Monitor INR.

Warnings

Pregnancy

Category B

Toxicity

LD50 >2000 mg/kg (oral, mouse)

Overdose

Symptoms: GI symptoms (nausea, vomiting, diarrhea), crystalluria. Treatment: discontinue, supportive care, maintain hydration. Removable by hemodialysis.

References

Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.