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# Drug Information Request: Amoxicillin
## Overview
Amoxicillin is a beta-lactam antibiotic (aminopenicillin) that acts by inhibiting bacterial cell wall synthesis. It provides bactericidal activity against susceptible Gram-positive and select Gram-negative organisms. It possesses improved oral bioavailability compared to ampicillin.
## Primary Indications
Common indications include acute otitis media (AOM), community-acquired pneumonia (CAP), pharyngitis (Group A Streptococcus), and sinusitis. It is also used for *H. pylori* eradication and bacterial endocarditis prophylaxis.
## Adult Dosing
Standard dosing for mild-to-moderate infections is 500 mg every 8-12 hours or 875 mg every 12 hours. For severe infections, doses up to 1 g every 8 hours may be used. For antibiotic prophylaxis (dental), the dose is 2 g orally 30-60 minutes before the procedure.
## Pediatric Dosing
Standard dosing for most infections (e.g., AOM) is 80–90 mg/kg/day divided every 12 hours. For mild infections (e.g., pharyngitis), 40–50 mg/kg/day divided every 8-12 hours is often used. Maximum pediatric dose typically follows the adult maximum dose (e.g., 875 mg per dose).
## Dose Adjustments
Renal impairment requires adjustment when CrCl < 30 mL/min. For CrCl 10–30 mL/min, use 250–500 mg every 12 hours. For CrCl < 10 mL/min, use 250–500 mg every 24 hours. No hepatic adjustment is required.
## Contraindications
Hypersensitivity to amoxicillin or any penicillin. History of severe allergic reactions (anaphylaxis, Stevens-Johnson syndrome) to any beta-lactam requires extreme caution or avoidance due to potential cross-reactivity.
## Adverse Effects
Common: Diarrhea, nausea, vomiting, and rash.
Serious/Rare: *Clostridioides difficile*-associated diarrhea (CDAD), severe hypersensitivity reactions (anaphylaxis), and blood dyscrasias.
## Key Drug Interactions
* **Probenecid:** Decreases renal excretion of amoxicillin, increasing serum levels.
* **Methotrexate:** May decrease clearance of methotrexate, potentially increasing toxicity.
* **Oral Contraceptives:** Potential for reduced efficacy (evidence is inconsistent; use backup method during therapy).
* **Warfarin:** May increase INR/risk of bleeding (monitor closely).
## Monitoring
Monitor for signs of hypersensitivity (rash, urticaria, wheezing). Assess clinical response (e.g., fever reduction, symptom improvement) within 48–72 hours. Monitor renal function in patients on long-term therapy or those with existing insufficiency.
## Clinical Pearls
* Amoxicillin is not effective against beta-lactamase-producing organisms.
* For suspected penicillin-resistant *Streptococcus pneumoniae* in AOM, the high-dose regimen (90 mg/kg/day) is essential.
* Advise patients to complete the full course of therapy even if symptoms improve.
* GI side effects, especially diarrhea, are common; taking with food may mitigate nausea but does not significantly alter absorption.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult current, reputable clinical resources (e.g., Lexicomp, UpToDate) and local institutional guidelines before prescribing or administering medication, as clinical protocols and safety data may change.
