Urticaria, pruritus, rash, fever and chills, reactions resembling serum sickness, eosinophilia, joint pain or inflammation, edema, erythema, genital and anal pruritus, angioedema, shock, hypotension, vasodilation, Stevens-Johnson syndrome, erythema multiforme, toxic epidermal necrolysis, and exfoliative dermatitis have been reported. Anaphylaxis, including a few fatalities, has occurred rarely. Hypersensitivity reactions occur most frequently in patients with a history of allergy, particularly to penicillins.
Positive direct and indirect antiglobulin (Coombs') test results have been reported. Non-immunologic positive Coombs' test results are most likely to occur in patients who have received large doses of Cefalexin or who have impaired renal function or hypoalbuminemia.
Other adverse hematologic effects of Cefalexin include rare, mild and transient neutropenia, thrombocytopenia, leukocytosis, granulocytosis, monocytosis, lymphocytopenia, basophilia, and reversible leukopenia.
Renal and Genitourinary Effects:
Transient increases in BUN and serum creatinine concentrations, renal dysfunction, and toxic nephropathy.
Genitourinary effects reported with Cefalexin therapy include vaginitis, vaginal moniliasis, genital pruritus, and menstrual irregularities.
Transient increases in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transferases (γ-glutamyl transpeptidase, GGT, GGTP), and alkaline phosphatase concentrations, increased serum concentrations of bilirubin and/or LDH, decreased serum albumin and/or total protein, hepatic dysfunction including cholestasis, have been reported with Cefalexin therapy.
Nausea, vomiting, diarrhea, abdominal pain, tenesmus, epigastric pain/dyspepsia, decreased appetite/anorexia, glossitis, flatulence, candidiasis, taste alteration, decreased salivation, and heartburn.
Rarely, antibiotic-associated pseudomembranous colitis, caused by toxin-producing Clostridia resistant to Cefalexin, has occurred during or following discontinuance of Cefalexin. Appropriate measures should be undertaken (i.e., sigmoidoscopy, appropriate bacteriologic studies, and treatment with fluid, electrolyte and protein supplementation) as needed. Antiperistaltic agents may prolong and/or worsen the condition and should be avoided if pseudomembranous colitis is suspected. If colitis is moderate to severe or is not relieved by discontinuance of the cephalosporin, appropriate anti-infective therapy should be administered. Isolation of the patient may be advisable. Other causes of colitis should be considered.
Other Adverse Effects:
Other adverse effects reported with Cefalexin therapy include chest pain, pleural effusion, dyspnea or respiratory distress, cough, and rhinitis. Increased or decreased serum glucose concentration has also been reported.