Cefaclor should not be used in critically ill patients because parenteral antibiotic therapy is more appropriate in these patients. Safety and efficacy of cefaclor for use in children less than 1 month of age have not been established. The safety of the use of cefaclor during pregnancy has not been established. Cephalosporins are considered to be unsafe for use in patients with acute porphyria. Cefaclor should not be given to patients who are hypersensitive to it or to other cephalosporins.
Care is also necessary in patients with known histories of allergy.
If any allergic reaction occurs, the medication should be discontinued and the patient treated with appropriate agents, eg, adrenaline, corticosteroids, aminophylline and antihistamines. Efficacy of cefaclor in the prophylaxis of rheumatic fever has not been established. The adult dosage is 250 mg every eight hours. For more severe infections, such as pneumonia, or those caused by less susceptible organisms, the dosage may be doubled. These reactions are apparently due to hypersensitivity and usually occur after or during a second course of cefaclor therapy.