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Peds Calc

Safety Information

Keflex Contraindications & InteractionsWhen Not to Use & Important Drug Interactions

Understanding when Keflex should not be used is essential for your child's safety. Most importantly, avoid this medication if your child has had serious allergic reactions to cephalosporin antibiotics or severe immediate reactions to penicillin.

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

Keflex contraindications include absolute restrictions (cephalosporin allergies) and relative cautions (severe immediate penicillin reactions, severe renal impairment). Its excellent safety profile and minimal drug interactions make it one of the safest antibiotics for most children.

Contraindications

Absolute Contraindications (Never Use)

Unspecified condition

Any history of immediate hypersensitivity reactions to cephalexin or other cephalosporin antibiotics

Relative Contraindications (Use With Caution)

Unspecified condition

History of immediate anaphylactic reaction to penicillin antibiotics within 1 hour of administration

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

moderate interaction

Specific drugs: See description

Effect: Increased cephalexin levels and prolonged half-life

How it happens: Blocks renal tubular secretion of cephalexin

Management: Monitor for increased side effects; dose reduction may be needed

minor interaction

Specific drugs: See description

Effect: Slight increase in metformin levels

How it happens: Possible competition for renal elimination pathways

Management: Monitor blood glucose more closely if applicable

very_low interaction

Specific drugs: See description

Effect: Theoretical slight reduction in contraceptive efficacy

How it happens: Possible minimal disruption of enterohepatic circulation

Management: Consider backup contraception if concerned

Disease State Considerations

Inflammatory bowel disease (IBD)

Unknown

No information available

Phenylketonuria (PKU)

Unknown

No information available

Safety Screening Tools

Monitoring Requirements

Hypersensitivity reactions

Frequency

Continuous during first dose, then daily

Gastrointestinal effects

Frequency

Daily monitoring

Treatment effectiveness

Frequency

Monitor response to therapy

Renal function (if impaired)

Frequency

Monitor symptoms, labs if indicated

Clinical References

Cephalexin Prescribing Information and Contraindicationsโ€ขFDA Drug Database (2023)regulatory standardPediatric data
Beta-Lactam Cross-Reactivity in Pediatric Patientsโ€ขJournal of Allergy and Clinical Immunology (2023)allergy reviewPediatric data
First-Generation Cephalosporin Safety in Childrenโ€ขPediatric Infectious Disease Journal (2022)safety reviewPediatric data
Drug Interactions with Pediatric Antibioticsโ€ขPediatric Clinics of North America (2023)interaction reviewPediatric data