What is Keflex (cephalexin)?

Keflex (cephalexin) is a cephalosporin antibiotic used to treat infections caused by bacteria including middle ear infections (otitis media), tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, urinary tract (UTIs), and skin and bone infections.

Drug interactions of Keflex include BCG and typhoid vaccines. There are no adequate and well-controlled studies of Keflex in pregnant women. Keflex should be used during pregnancy only if clearly needed. Keflex is excreted in breast milk. Keflex should be used with caution or stopped when breastfeeding.

What are the side effects of Keflex?

What are the common side effects of Keflex?

Common side effects of Keflex include

What are the serious side effects of Keflex?

Serious side effects of Keflex include

Serious but rare allergic reactions include

Is Keflex addictive?

No information provided

What drugs interact with Keflex?

Metformin

Administration of Keflex with metformin results in increased plasma metformin concentrations and decreased renal clearance of metformin.

Careful patient monitoring and dose adjustment of metformin is recommended in patients concomitantly taking Keflex and metformin.

Probenecid

The renal excretion of Keflex is inhibited by probenecid. Co-administration of probenecid with Keflex is not recommended.

Interaction With Laboratory Or Diagnostic Testing

A false-positive reaction may occur when testing for the presence of glucose in the urine using Benedict's solution or Fehling's solution.

Keflex side effects list for healthcare professionals

The following serious events are described in greater detail in the Warning and Precautions section:

  • Hypersensitivity reactions
  • Clostridium difficile-associated diarrhea
  • Direct Coombs' Test Seroconversion
  • Seizure Potential
  • Effect on Prothrombin Activity
  • Development of Drug-Resistant Bacteria

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice

In clinical trials, the most frequent adverse reaction was diarrhea. Nausea and vomiting, dyspepsia, gastritis, and abdominal pain have also occurred. As with penicillins and other cephalosporins, transient hepatitis and cholestatic jaundice have been reported.

Other reactions have included hypersensitivity reactions, genital and anal pruritus, genital candidiasis, vaginitis and vaginal discharge, dizziness, fatigue, headache, agitation, confusion, hallucinations, arthralgia, arthritis, and joint disorder. Reversible interstitial nephritis has been reported. Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight elevations in aspartate transaminase (AST) and alanine transaminase (ALT) have been reported.

In addition to the adverse reactions listed above that have been observed in patients treated with Keflex, the following adverse reactions and other altered laboratory tests have been reported for cephalosporin class antibacterial drugs:

Other Adverse Reactions

Fever, colitis, aplastic anemia, hemorrhage, renal dysfunction, and toxic nephropathy.

Altered Laboratory Tests

Prolonged prothrombin time, increased blood urea nitrogen (BUN), increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated lactate dehydrogenase (LDH), pancytopenia, leukopenia, and agranulocytosis.

Summary

Keflex (cephalexin) is a cephalosporin antibiotic used to treat infections caused by bacteria including middle ear infections (otitis media), tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, urinary tract (UTIs), and skin and bone infections. Headaches, dizziness, and gastrointestinal side effects are common.

Treatment & Diagnosis

Medications & Supplements

Prevention & Wellness

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Medically Reviewed on 8/10/2021
References
FDA Prescribing Information

Professional side effects list and drug interactions sections courtesy of the U.S. Food and Drug Administration