Keflex is indicated for the treatment of the following infections when caused by susceptible strains of the designated microorganisms:

Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes.

Skin and skin structure infections caused by Staphylococcus aureus and/or Streptococcus pyogenes.

Bone infections caused by Staphylococcus aureus and/or Proteus mirabilis.

Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis,and Klebsiella pneumoniae.

The adult dosage ranges from 1 to 4 g daily in divided doses. The 333 mg and 750 mg strengths should be administered such that the daily dose is within 1 to 4 grams per day. The usual adult dose is 250 mg every 6 hours.

Gastrointestinal— Onset of pseudomembranous colitis may occur during or after antibacterial treatment. (See WARNINGS.) Nausea and vomiting have been reported rarely. The most frequent side effect has been diarrhea. It was very rarely severe enough to warrant cessation of therapy. Dyspepsia, gastritis, and abdominal pain have also occurred. As with some penicillins and some other cephalosporins, transient hepatitis and cholestatic jaundice have been reported rarely.

Hypersensitivity— Allergic reactions in the form of rash, urticaria, angioedema, and, rarely, erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis have been observed. These reactions usually subsided upon discontinuation of the drug. In some of these reactions, supportive therapy may be necessary. Anaphylaxis has also been reported.

Keflex is contraindicated in patients with known allergy to the cephalosporin group of antibiotics.

There is some clinical and laboratory evidence of partial cross-allergenicity of the penicillins and the cephalosporins. Patients have been reported to have had severe reactions (including anaphylaxis) to both drugs.

Patients should be counseled that antibacterial drugs including Keflex should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Keflex is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Keflex or other antibacterial drugs in the future.