Amoxil®

Amoxicillin · oral capsule

Antibiotic

Approved uses

Infections due to susceptible beta-lactamase negative isolates: ear, nose and throat, genitourinary tract, skin and skin structure, lower respiratory tract; H. pylori with duodenal ulcer disease in adults

Adults and patients over 40 kg: 500 mg every 12 hours or 250 mg every 8 hours, or 875 mg every 12 hours or 500 mg every 8 hours for severe and lower respiratory infection. Pediatric patients 3 months and older under 40 kg: 20 to 45 mg/kg/day divided every 8 to 12 hours. H. pylori triple therapy: 1 g twice daily with clarithromycin 500 mg and lansoprazole 30 mg for 14 days.

OFF-LABELNot in the FDA label for this product

Preseptal (periorbital) cellulitis

Label regimen for skin and skin structure infection: adults and patients over 40 kg 500 mg every 12 hours or 250 mg every 8 hours, or 875 mg every 12 hours or 500 mg every 8 hours if severe; pediatric patients 3 months and older under 40 kg 20 to 45 mg/kg/day divided every 8 to 12 hours.

Narrative review · no trials

A narrative review of pediatric preseptal and orbital cellulitis lists amoxicillin among the antibacterials often used, notes significant variation in agent selection, supports transition from IV to oral therapy once clinical and laboratory improvement is clear, and reports total durations trending toward about 2 weeks. It offers practice pattern and antimicrobial stewardship guidance, not comparative efficacy data. Coverage is the practical limit: the label confines the skin and skin structure indication to beta-lactamase negative Streptococcus spp., Staphylococcus spp., and E. coli, so beta-lactamase producing staphylococci fall outside it.

Stimes GT, Girotto JE. Applying Pharmacodynamics and Antimicrobial Stewardship to Pediatric Preseptal and Orbital Cellulitis. Paediatr Drugs. 2019;21(6):427-438 (review). PMID 31608423. Dose and spectrum limit: FDA label, Dosage and Administration (2.2) and Indications and Usage (1).

Contraindications

History of a serious hypersensitivity reaction such as anaphylaxis or Stevens-Johnson syndrome to amoxicillin or to other beta-lactams, including penicillins and cephalosporins.

Available Forms

Tablets 500 mg and 875 mg; capsules 250 mg and 500 mg; chewable tablets 125 mg and 250 mg; for oral suspension 200 mg/5 mL in 50, 75 and 100 mL, 250 mg/5 mL in 80, 100 and 150 mL, 400 mg/5 mL in 50, 75 and 100 mL

Mechanism of Action

Aminopenicillin; bactericidal against susceptible bacteria during active multiplication by inhibiting cell wall biosynthesis. Resistance is mediated primarily by beta-lactamases that cleave the beta-lactam ring, and the label accordingly restricts every indication to beta-lactamase negative isolates.

Warnings & Precautions

Anaphylactic reactions: Serious and occasionally fatal reactions have occurred on penicillin therapy, more often parenterally but also on oral penicillins; risk is higher with a history of penicillin hypersensitivity or sensitivity to multiple allergens, and individuals with penicillin hypersensitivity have had severe reactions to cephalosporins.
Severe cutaneous adverse reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS, and acute generalized exanthematous pustulosis; monitor any rash closely and discontinue if lesions progress.
Drug-induced enterocolitis syndrome: Non-IgE mediated reaction with protracted vomiting 1 to 4 hours after ingestion in the absence of skin or respiratory symptoms, most cases in patients 18 years or younger; may include pallor, lethargy, hypotension, shock, diarrhea within 24 hours, and leukocytosis with neutrophilia.
Clostridioides difficile associated diarrhea: Ranges from mild diarrhea to fatal colitis, may be refractory and require colectomy, and has been reported over 2 months after antibacterial administration.
Skin rash in mononucleosis: A high percentage of patients with mononucleosis who receive it develop an erythematous rash; do not administer in mononucleosis.
Allopurinol interaction: Concurrent administration increases the incidence of rash compared with amoxicillin alone.
Oral anticoagulant interaction: Abnormal prolongation of prothrombin time with increased INR has been reported; monitor and adjust anticoagulant dosing.
Oral contraceptive interaction: Efficacy of combined estrogen and progesterone contraceptives may fall through reduced estrogen reabsorption.

Common Side Effects

Systemic, greater than 1%: Diarrhea, rash, vomiting, nausea.
Hypersensitivity: Anaphylactic and anaphylactoid reactions including shock, angioedema, urticaria, serum sickness-like reactions, hypersensitivity vasculitis (postmarketing, frequency not estimable).
Severe cutaneous adverse reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS, acute generalized exanthematous pustulosis, erythema multiforme, exfoliative dermatitis, linear IgA bullous dermatosis.
Gastrointestinal: Drug-induced enterocolitis syndrome, black hairy tongue, hemorrhagic or pseudomembranous colitis; colitis onset may occur during or after treatment.
Hepatic: Moderate AST and ALT rise of unknown significance; cholestatic jaundice, hepatic cholestasis, acute cytolytic hepatitis.
Hematologic: Anemia including hemolytic anemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, leukopenia, agranulocytosis; usually reversible on discontinuation and believed to be hypersensitivity phenomena.
Central nervous system: Reversible hyperactivity, agitation, anxiety, insomnia, confusion, convulsions, behavioral changes, aseptic meningitis, dizziness.
Renal: Crystalluria.
Dental: Tooth discoloration, brown, yellow or gray, mostly in pediatric patients and in most cases reduced or eliminated by brushing or dental cleaning.

Pregnancy & Lactation

Pregnancy: Category B. Reproduction studies in mice and rats at up to 2000 mg/kg (3 and 6 times the 3 g human dose by body surface area) showed no evidence of fetal harm; there are no adequate and well-controlled studies in pregnant women, so use only if clearly needed.

Lactation: Penicillins are excreted in human milk and use by a nursing mother may sensitize the infant; exercise caution.

Pediatric Use

Effectiveness established for the labeled non-ocular indications; not established for H. pylori.