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Cefaclor Side Effects

For the Consumer

Applies to cefaclor: extended-release tablets

Other dosage forms:

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Headache; mild diarrhea; nausea; sinus infection; tiredness; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur while taking cefaclor:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bloody stools; fever; seizures; severe diarrhea; stomach pain or cramps; urge to have a bowel movement; vaginal irritation or discharge.

For Healthcare Professionals

Applies to cefaclor: oral capsule, oral powder for reconstitution, oral tablet chewable, oral tablet extended release


If diarrhea occurs and it is unresponsive to discontinuation of the drug and/or standard therapy, pseudomembranous colitis should be considered.[Ref]

Gastrointestinal side effects have included diarrhea, nausea, vomiting, and abdominal pain. Extended-release cefaclor has been associated with diarrhea (3.8%), nausea (3.4%), and anorexia, constipation, dyspepsia, flatulence, gastritis, nausea and vomiting, and vomiting in 0.1% to 1% of patients. Pseudomembranous colitis has been reported in patients treated with cephalosporins.[Ref]


Anaphylactic reactions are rare, but may occur, especially in patients with a history of penicillin allergy.

Serum-sickness-like reactions are more frequent in pediatric patients and following a second or subsequent course of cefaclor and have been characterized by erythema multiforme, rash, arthritis, and/or arthralgia with or without fever.[Ref]

Hypersensitivity reactions have included rash, morbilliform eruptions (1%), pruritus, serum-sickness-like reactions, urticaria, anaphylactic reaction, Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylactoid reaction, and angioedema.[Ref]


Hepatic side effects have included slight elevations AST, ALT, and alkaline phosphatase in 2.5% of patients. Extended-release cefaclor has been associated with increased ALT (0.3%), increased alkaline phosphatase (0.3%), increased bilirubin (0.3%), increased creatine phosphokinase (0.7%), and increased GGT (0.2%). Cephalosporins as a class have been associated with elevated LDH, hepatic dysfunction, and cholestasis.[Ref]


One case report of acute interstitial nephritis and nonoliguric renal failure has been reported following cefaclor therapy. (Reversible fever, azotemia, pyuria, and eosinophiluria are the hallmarks of cephalosporin-induced interstitial nephritis.)[Ref]

Renal side effects have included transient elevations in blood urea nitrogen (BUN) and serum creatinine in 0.2% of patients, reversible interstitial nephritis (rare), and abnormal urinalysis (0.5%). Extended-release cefaclor has been associated with increased BUN (0.2%), and increased creatinine (0.5%). Cephalosporins as a class have been associated with toxic nephropathy, reversible interstitial nephritis, and renal dysfunction.[Ref]


Hematologic side effects have included eosinophilia (2%), positive Coombs' test (less than 0.5%), leukopenia, thrombocytosis, transient thrombocytopenia (rare), transient lymphocytosis, hemolytic anemia, aplastic anemia, agranulocytosis, and reversible neutropenia. Extended-release cefaclor has been associated with increased eosinophils (0.3%), decreased erythrocyte count (0.3%), decreased hemoglobin (0.2%), decreased lymphocytes (0.3%), increased mean cell volume (0.7%), decreased segmented neutrophils (0.3%), and decreased platelet count (0.4%). Cephalosporins as a class have been associated with hemorrhage and pancytopenia.[Ref]


Genitourinary side effects have included genital pruritus and vaginitis in less than 1% of patients. Extended-release cefaclor has been associated with vaginitis (2.4%) and vaginal moniliasis (2.2%), and dysmenorrhea, dysuria, leukorrhea, menstrual disorder, and nocturia in 0.1% to 1% of patients. Cephalosporins as a class have been associated with false-positive tests for urine glucose.[Ref]

Nervous system

Nervous system side effects have rarely included reversible hyperactivity, agitation, nervousness, insomnia, confusion, hypertonia, dizziness, hallucinations, and somnolence. Extended release cefaclor has been associated with headache in 4.9% of patients, and dizziness, insomnia, nervousness, somnolence, and tremor in 0.1% to 1% of patients, and paresthesia and vertigo. Some cephalosporins have been associated with seizures, primarily when dosages were not reduced in renally impaired patients.[Ref]


Other side effects associated with extended-release cefaclor have included abdominal pain (1.6%), back pain (1%), and accidental injury, chest pain, chills, ear pain, fever, flu syndrome, infection, malaise, neck pain, otitis media, pain, and surgical procedure in 0.1% to 1% of patients. Cephalosporins as a class have been associated with abdominal pain, fever, and superinfection.[Ref]


Respiratory side effects associated with extended-release cefaclor have included rhinitis (3.9%), increased cough (1.5%), pharyngitis (1.4%), and asthma, bronchitis, lung disorder, respiratory disorder, and sinusitis in 0.1% to 1% of patients.[Ref]


Dermatologic side effects have included pruritus, maculopapular rash, rash, and urticaria.[Ref]


Musculoskeletal side effects associated with extended-release cefaclor have included arthralgia and myalgia in 0.1% to 1% of patients.[Ref]


Cardiovascular side effects associated with extended-release cefaclor have included congestive heart failure (0.1% to 1%), edema (0.1% to 1%), palpitation (0.1% to 1%), peripheral edema (0.1% to 1%), hypotension, face edema, vasodilatation, and syncope.[Ref]


Ocular side effects associated with extended-release cefaclor have included conjunctivitis (0.1% to 1%).[Ref]


Endocrine side effects associated with extended-release cefaclor have included sweating (0.1% to 1%).[Ref]


Metabolic side effects associated with extended-release cefaclor have included decreased albumin (0.3%), decreased calcium (0.7%), increased creatine phosphokinase (0.7%), increased phosphorus (0.7%), increased potassium (0.4%), decreased sodium (0.3%), and increased sodium (0.4%).[Ref]


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4. Goumas P, Naxakis S, Bassaris C, Skoutelis A "Comparative efficacy and tolerability of clarithromycin and cefaclor in the treatment of outpatients with acute maxillary sinusitis." Clin Drug Invest 13 (1997): 128-33

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6. Boyd LW "Cefaclor-associated serum sickness." Med J Aust 169 (1998): 443-4

7. Ackley AM, Felsher J "Adverse reactions to cefaclor." South Med J 74 (1981): 1550

8. Reynolds RD "Cefaclor and serum sickness-like reaction." JAMA 276 (1996): 950

9. Beghetti M, Wilson GJ, Bohn D, Benson L "Hypersensitivity myocarditis caused by an allergic reaction to cefaclor." J Pediatr 132 (1998): 172-3

10. Filipe P, Almeida RSLS, Rodrigo FG "Occupational allergic contact dermatitis from cephalosporins." Contact Dermatitis 34 (1996): 226

11. Hama R, Mori K "High incidence of anaphylactic reactions to cefaclor." Lancet 06/11/88 (1988): 1331

12. Grouhi M, Hummel D, Roifman CM "Anaphylactic reaction to oral cefaclor in a child." Pediatrics 103 (1999): e50

13. Christensen JC, Swenson E, Gooch WM, Herrod JN "Comparative efficacy and safety of cefprozil (BMY-28100) and cefaclor in the treatment of acute group A beta-hemolytic streptococcal pharyngitis." Antimicrob Agents Chemother 35 (1991): 1127-30

14. Pommer W, Krause PH, Berg PA, et al "Acute interstitial nephritis and non-oliguric renal failure after cefaclor treatment." Klin Wochenschr 64 (1986): 290-3

15. "Multum Information Services, Inc. Expert Review Panel"

Not all side effects for cefaclor may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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