Cephalexin

Absorption

Well absorbed from the upper gastrointestinal tract with nearly 100% oral bioavailability. Cephalexin is not absorbed in the stomach but is absorbed in the upper intestine.
Patients taking 250mg of cephalexin reach a maximum plasma concentration of 7.7mcg/mL and patients taking 500mg reach 12.3mcg/mL.

Toxicity

Symptoms of overdose include blood in the urine, diarrhea, nausea, upper abdominal pain, and vomiting. An overdose is generally managed through supportive treatment as diuresis, dialysis, hemodialysis, and charcoal hemoperfusion are not well studied in this case.
The oral median lethal dose of cephalexin in rats is >5000 mg/kg. The oral LD50 in a monkey is >1g/kg and the lowest dose causing a toxic effect in humans is 14mg/kg.
Cephalexin has not been shown to be harmful in pregnancy and is not associated with teratogeniticy. Cephalexin is present in breast milk, though infants may be exposed to <1% of the dose given to the mother. The effects of breast milk exposure to cephalexin have not been established and so caution must be exercised and the risk and benefit of cephalexin use in breastfeeding must be weighed.
Cephalexin has not been studied for carcinogenicity or mutagenicity. Cephalexin has no affect on fertility in rats.

Description

Use of the ampicillin-type side chain conveys oral activity to cephalexin. Whereas it no longer has an activating side chain at C-3 and, as a consequence, is somewhat less potent, it does not undergo metabolic deactivation and, thus, maintains potency. It is rapidly and completely absorbed from the GI tract and has become quite popular. Somewhat puzzling is the fact that the use of the ampicillin side chain in the cephalosporins does not result in a comparable shift in antimicrobial spectrum. Cephalexin, like the other first-generation cephalosporins is active against many Gram-positive aerobic cocci but is limited against Gram-negative bacteria. It is a widely used drug, particularly against Gram-negative bacteria causing urinary tract infections, Gram-positive infections (Staphyl ococcus aureus, Streptococcus pneumoni ae and Streptococcus pyogenes) of soft tissues, pharyngitis, and minor wounds.

The Uses of Cephalexin

Antibacterial.

Background

Cephalexin is the first of the first generation cephalosporins. This antibiotic contains a beta lactam and a dihydrothiazide. Cephalexin is used to treat a number of susceptible bacterial infections through inhibition of cell wall synthesis. Cephalexin was approved by the FDA on 4 January 1971.

What are the applications of Application

Cephalexin is a semi-synthetic, cephalosporin antibiotic

Indications

Cephalexin is indicated for the treatment of certain infections caused by susceptible bacteria. These infections include respiratory tract infections, otitis media, skin and skin structure infections, bone infections, and genitourinary tract infections.

Pharmacokinetics

Cephalexin (also called Cefalexin) is a first generation cephalosporin antibiotic. It is one of the most widely prescribed antibiotics, often used for the treatment of superficial infections that result as complications of minor wounds or lacerations. It is effective against most gram-positive bacteria through its inihibition of the cross linking reaction between N-acetyl muramicacid and N-acetylglucosamine in the cell wall, leading to cell lysis.

Metabolism

Cephalexin is not metabolized in the body.