CEPHALEXIN Drug Interactions: What You Need to Know

INTERACTIONS

• Metformin: increased metformin concentrations. Monitor for hypoglycemia. ( Error! Hyperlink reference not valid. )
• Probenecid-The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended. ( Error! Hyperlink reference not valid. )
• Administration of cephalexin may result in a false-positive reaction glucose in the urine. ( Error! Hyperlink reference not valid. )

7.1 Metformin Administration of cephalexin 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 cephalexin and metformin <span class="opacity-50 text-xs">[see Error! Hyperlink reference not valid. ]</span>.

7.2 Probenecid The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended.

7.3 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.

Cephalexin capsules are contraindicated in patients with known hypersensitivity to cephalexin or other members of the cephalosporin class of antibacterial drugs. Patients with known hypersensitivity to cephalexin or other members of the cephalosporin class of antibacterial drugs. ( Error! Hyperlink reference not valid. )

AND PRECAUTIONS

• Serious hypersensitivity (anaphylactic) reactions : Prior to use, inquire regarding history of hypersensitivity to beta-lactam antibacterial drugs. Discontinue the drug if signs or symptoms of an allergic reaction occur and institute supportive measures. ( Error! Hyperlink reference not valid. )
• Clostridium difficile -associated diarrhea (CDAD ): Evaluate if diarrhea occurs. ( Error! Hyperlink reference not valid. )
• Direct Coombs’ Test Seroconversion : If anemia develops during or after cephalexin therapy, evaluate for drug-induced hemolytic anemia. ( Error! Hyperlink reference not valid. )
• Seizure Potential : Use lower dose in patients with renal impairment. ( Error! Hyperlink reference not valid. )

5.1 Hypersensitivity Reactions Allergic reactions in the form of rash, urticaria, angioedema, anaphylaxis, erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis have been reported with the use of cephalexin. Before therapy with cephalexin is instituted, inquire whether the patient has a history of hypersensitivity reactions to cephalexin, cephalosporins, penicillins, or other drugs. Cross-hypersensitivity among beta-lactam antibacterial drugs may occur in up to 10% of patients with a history of penicillin allergy. If an allergic reaction to cephalexin occurs, discontinue the drug and institute appropriate treatment.

5.2 Clostridium difficile -Associated Diarrhea Clostridium difficile - associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including cephalexin, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile . C. difficile produces toxins A and B, which contribute to the development of CDAD. Hypertoxin-producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated.

5.3 Direct Coombs’ Test Seroconversion Positive direct Coombs’ tests have been reported during treatment with the cephalosporin antibacterial drugs including cephalexin. Acute intravascular hemolysis induced by cephalexin therapy has been reported. If anemia develops during or after cephalexin therapy, perform a diagnostic work-up for drug-induced hemolytic anemia, discontinue cephalexin and institute appropriate therapy.

5.4 Seizure Potential Several cephalosporins have been implicated in triggering seizures, particularly in patients with renal impairment when the dosage was not reduced. If seizures occur, discontinue cephalexin. Anticonvulsant therapy can be given if clinically indicated.

5.5 Prolonged Prothrombin Time Cephalosporins may be associated with prolonged prothrombin time. Those at risk include patients with renal or hepatic impairment, or poor nutritional state, as well as patients receiving a protracted course of antibacterial therapy, and patients receiving anticoagulant therapy. Monitor prothrombin time in patients at risk and manage as indicated.

5.6 Development of Drug-Resistant Bacteria Prescribing cephalexin in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria. Prolonged use of cephalexin may result in the overgrowth of nonsusceptible organisms. Careful observation of the patient is essential. If superinfection occurs during therapy, appropriate measures should be taken.