First-generation Cephalosporins

The first-generation cephalosporins are alternatives to penicillin VK for the treatment of odontogenic infections. The oral dosage forms of this class are cefadroxil (Duracef®), cephalexin (Keflex®), and cephradine (Velosef®). They are indicated as alternatives to penicillin VK in early infection because they are bacterially effective against aerobes but not anaerobes. They are active against gram-positive staphylococci and streptococci, but ineffective against enterococci. The rate of cross reactivity between cephalosporins and penicillins is 1% when the allergic reaction to penicillin is delayed. It should be used with caution in those patients exhibiting anaphylactoid reactions.

Contraindications: Hypersensitivity to cephalexin, any component of the formulation, or other cephalosporins.

Warnings/Precautions: Modify dosage in patients with severe renal impairment; prolonged use may result in superinfection. Use with caution in patients with a history of penicillin allergy. May cause antibiotic associated colitis.

Cephalexin (Keflex®) is the first-generation cephalosporin most often used to treat odontogenic infections.

The usual daily oral dose for treating odontogenic infections in children is:

Children under 12 years: 25-50 mg/kg/day in divided doses every 6 hours. For severe infections the dosage is 50-100 mg/kg/day in divided doses every 6 hours with a maximum does of 3 g/day for 10 days.
Children over 12 and adults: 250-1000 mg every 6 hours with a maximum of 4 g/day.
Supplied as a 125, 250 mg/5 ml suspension and 250 and 500 mg capsules.

Sample cephalexin prescription for a 3-year-old patient weighing 12 kg (25 lb) with facial swelling:

Rx: Cephalexin 125 mg/5 ml
Disp: 200 ml
Sig: 1 tsp every 6 hours for 10 days