Keflex (Cephalexin)

Drug Nomenclature

Keflex (Cephalexin/Cefalexin) 250mg/500mg/750mg Tablets

Pharmacopoeias

Keflex (Cephalexin/Cefalexin) 250mg/500mg/750mg Tablets. In China, Europe, Japan, US, and Vietnam

European Pharmacopoeia

Keflex (Cephalexin/Cefalexin) 250mg/500mg/750mg Tablets, 6th ed., 2008 and Supplements 6.1 and 6.2 (Cefalexin Monohydrate). A white or almost white crystalline powder. Sparingly soluble in water; practically insoluble in alcohol. A 0.5% solution in water has a pH of 4.0 to 5.5. Protect from light.

The United States Pharmacopeia

A white to off-white crystalline powder. Slightly soluble in water; practically insoluble in alcohol, in chloroform, and in ether. pH of a 5% suspension in water is between 3.0 and 5.5. Store in airtight containers.

Cefalexin Hydrochloride

Drug Nomenclature

Pharmacopoeias Keflex (Cephalexin/Cefalexin) 250mg/500mg/750mg Tablets. In US. The United States Pharmacopeia 31, 2008 (Cephalexin Hydrochloride). A white to off-white crystalline powder. Soluble 1 in 100 in water, in acetone, in acetonitrile, in alcohol, in dimethylformamide, and in methyl alcohol; practically insoluble in chloroform, in ether, in ethyl acetate, and in isopropyl alcohol. pH of a 1 % solution in water is between 1.5 and 3.0. Store in airtight containers.

Adverse Effects and Precautions

As for Cefalotin Sodium. The most common adverse effects of cefalexin and other oral cephalosporins are generally gastrointestinal disturbances and hypersensitivity reactions. Pseudomembranous colitis has been reported. Porphyria. Cephalexin is considered to be unsafe in patients with porphyria although there is conflicting experimental evidence of porphyrinogenicity.

Interactions

The renal excretion of cefalexin, and many other cephalosporins, is delayed by probenecid. Hormonal contraceptives. There have been isolated reports of cefalexin decreasing the efficacy of oestrogen-containing oral contraceptives. For a discussion of decreased efficacy of oral contraceptives and the need for additional contraceptive methods in patients taking broad-spectrum antibacterials, see under Hormonal Contraceptives.

Antimicrobial Action Keflex (Cephalexin/Cefalexin) 250/500/750mg Tablets

As for Cefalotin Sodium, although cefalexin is generally less potent. Some strains of Gram-negative bacteria may be inhibited only by the high concentrations achievable in the urinary tract. Haemophilus in-fluenzae is moderately resistant to cefalexin.

Pharmacokinetics Keflex (Cephalexin/Cefalexin) 250/500/750mg Tablets

Cephalexin is almost completely absorbed from the gastrointestinal tract and produces a peak plasma concentration of about 18 micrograms/mL 1 hour after a 500-mg oral dose. If cefalexin is taken with food, absorption may be delayed, but the total amount absorbed is not appreciably altered. Up to 15% of a dose is bound to plasma proteins.

The plasma half-life is about 1 hour; it increases with reduced renal function. Cephalexin is widely distributed in the body but does not enter the CSF in significant quantities. It crosses the placenta and small quantities are found in breast milk. Cefalexin is not metabolised. About 80% or more of a dose is excreted unchanged in the urine in the first 6 hours by glomerular filtration and tubular secretion; urinary concentrations greater than 1 mg/mL have been achieved after a dose of 500 mg.

Probenecid delays urinary excretion. Therapeutically effective concentrations may be found in the bile and some may be excreted by this route. Cephalexin is removed by haemodialysis and peritoneal dialysis.

Uses and Administration Keflex (Cephalexin/Cefalexin) 250/500/750mg Tablets

Cefalexin is a first-generation cephalosporin antibacterial. It is given orally for the treatment of susceptible infections including those of the respiratory and urinary tracts and of the skin (see under Choice of Antibacterial).

For severe infections, treatment with parenteral cephalosporins is to be preferred. Cephalexin is usually given as the monohydrate although the hydrochloride is sometimes used.

Doses are expressed in terms of the equivalent amount of anhydrous cefalexin; 1.05 g of cefalexin monohydrate and 1.16 g of cefalexin hydrochloride are each equivalent to about 1 g of anhydrous cefalexin.

The usual dose for adults is 1 to 2 g daily given in divided doses at 6-, 8-, or 12-hourly intervals; in severe or deep-seated infections the dose can be increased to up to 6 g daily but when high doses are required the use of a parenteral cephalosporin should be considered.

Children may be given 25 to 100 mg/kg daily in divided doses to a maximum of 4 g daily. For the prophylaxis of recurrent urinary-tract infection, cefalexin may be given in a dose of 125 mg at night. Cefalexin sodium or cefalexin lysine have been used parenterally. The dose of cefalexin may need to be reduced in renal impairment, see below.

Administration in renal impairment Keflex (Cephalexin/Cefalexin) 250/500/750mg Tablets

Doses of cefalexin may need to be reduced in patients with renal impairment. The BNF recommends the following maximum daily doses according to creatinine clearance (CC):

• CC 40 to 50 mL/minute: maximum 3 g daily
• CC 10 to 40 mL/minute: maximum 1.5 g daily
• CC less than 10 mL/minute: maximum 750 mg daily

Preparations

BP 2008: Cefalexin Capsules; Cefalexin Oral Suspension; Cefalexin Tablets;

USP 31: Cephalexin Capsules; Cephalexin for Oral Suspension; Cephalexin Tablets; Cephalexin Tablets for Oral Suspension.

Proprietary Preparations

Multi-ingredient