Adults

Adult dosage is usually 250-500 mg every 6 hours, but for pediatric suspension, it is mainly for children.

Elderly

Similar to adult dosage; caution and dose reduction may be necessary in those with impaired renal function.

Children

Typical dosage for children is 25-50 mg/kg/day in divided doses. For severe infections, the dose may be increased up to 100 mg/kg/day. Dosage depends on weight and severity of infection, typically 125-250 mg (5-10 mL) every 6-12 hours.

Renal_impairment

Dosage adjustment is necessary. For mild impairment (creatinine clearance 30-50 mL/min), maximum 1 g every 8-12 hours. For moderate (10-29 mL/min), maximum 500 mg every 8-12 hours. For severe (<10 mL/min), maximum 250 mg every 12 hours.

Onset

Within 30-60 minutes.

Excretion

Excreted rapidly by the kidneys via glomerular filtration and tubular secretion. Approximately 70-80% of the dose is excreted unchanged in the urine within 6 hours.

Half life

Approximately 0.5-1.2 hours in adults with normal renal function; longer in neonates and patients with renal impairment.

Absorption

Rapidly and completely absorbed from the gastrointestinal tract following oral administration. Peak plasma concentrations are reached within 1 hour.

Metabolism

Not significantly metabolized; about 10% is metabolized in the liver.

Warfarin

May enhance the anticoagulant effect, requiring closer monitoring of INR.

Metformin

Cefalexin may increase plasma concentrations of metformin.

Probenecid

May decrease the renal clearance of cefalexin, increasing its blood levels.

Aminoglycosides

May increase the risk of nephrotoxicity when co-administered.