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Peds Calc

Safety Information

Amoxicillin Contraindications & InteractionsWhen Not to Use & Important Drug Interactions

While amoxicillin is one of the safest antibiotics for children, understanding true contraindications versus common misconceptions helps ensure appropriate use. Most children with reported penicillin allergies can actually take amoxicillin safely when properly evaluated.

Clinical Utility: 10/10
4 Clinical Sources
Back to Amoxicillin Overview

Amoxicillin contraindications include true penicillin allergy (rare), infectious mononucleosis, and severe kidney disease. The majority of reported penicillin allergies in children are not true allergies but rather viral rashes or mild reactions that don't preclude future use. Drug interactions are minimal but include potential effects on oral contraceptives and anticoagulants.

Contraindications

Absolute Contraindications (Never Use)

True penicillin or amoxicillin allergy

Life-threatening reactions possible

Infectious mononucleosis (confirmed or suspected)

Rash can be severe and distressing but not dangerous

History of severe immediate reaction to any penicillin

Previous anaphylaxis predicts future severe reactions

Relative Contraindications (Use With Caution)

Severe kidney disease (CrCl <30 mL/min)

Risk of toxicity with standard doses

History of antibiotic-associated colitis (C. difficile)

Can cause severe colitis requiring hospitalization

Phenylketonuria (PKU) - for certain formulations

Can worsen PKU if phenylalanine-containing products used

Pregnancy & Lactation

This medication is generally considered safe during pregnancy and breastfeeding when used as directed. However, if you're pregnant or breastfeeding and need to give this medication to your child, it's always a good idea to discuss this with your healthcare provider to ensure it's the best choice for your specific situation.

Drug Interactions

minor interaction

Specific drugs: See description

Effect: Unknown effect

How it happens: May reduce gut bacteria that assist in hormone recycling

Management: Use backup contraception during treatment

moderate interaction

Specific drugs: See description

Effect: Unknown effect

How it happens: May potentiate anticoagulant effects

Management: Consult healthcare provider

moderate interaction

Specific drugs: See description

Effect: Unknown effect

How it happens: Reduces methotrexate clearance

Management: Consult healthcare provider

minor interaction

Specific drugs: See description

Effect: Unknown effect

How it happens: Increased risk of skin rash

Management: Consult healthcare provider

Safety Screening Tools

Clinical Pearls

80-90% of children labeled as 'penicillin allergic' can safely receive penicillins when properly evaluated

Evidence: highSource: Allergy and immunology literature, pediatric studies

Amoxicillin rash in mono patients (95% incidence) is not a true allergy and doesn't prevent future penicillin use

Evidence: highSource: Infectious disease literature

Cross-reactivity between penicillins and cephalosporins is <1% for true allergies, much lower than historically reported

Evidence: highSource: Recent meta-analyses and allergy studies

Timing of reaction matters: immediate reactions (<1 hour) are more concerning than delayed reactions (days)

Evidence: highSource: Allergology guidelines

Clinical References

Penicillin Allergy in Children: Separating Fact from Fictionโ€ขPediatric Allergy and Immunology (2023)systematic reviewPediatric data
Amoxicillin Safety Profile in Pediatric Populationsโ€ขJournal of Pediatric Pharmacology (2022)safety analysisPediatric data
Cross-Reactivity Between Penicillins and Cephalosporins: Updated Evidenceโ€ขClinical Infectious Diseases (2023)meta analysisPediatric data
Drug Interactions with Commonly Used Pediatric Antibioticsโ€ขPediatric Clinics of North America (2023)expert reviewPediatric data