Cephalexin : Therapeutic uses, Dosage & Side Effects
Cephalexin (Cefalexin) is an orally effective first generation cephalosporin, similar in spectrum to cefazolin, but less active against penicillinase producing Staphylococci and H. influenzae. It is one of the most commonly used cephalosporins.
Dose : 0.25-1 g 6-8 hourly (children 25-100 mg/kg/day)
Route : Oral
Onset of action : ?
Plasma Half-life : ~60 min.
Duration of action : ?
Bioavailability : Well absorbed
Plasma protein binding : 15%
Metabolism : 80% excreted unchanged in urine within 6 hours of administration
Pregnancy risk category : B
Chemical formula : C16H17N3O4S
IUPAC name : (7R)-3-Methyl-7- (α- D -phenylglycylamino) -3-cephem-4-carboxylic acid monohydrate
Trade name : Cephacillin, Sporidex, Alcephin, Cephaxin, Alcephin-LA, Keflex, Cepol, Ceporex, Panixine, Biocef, Zartan
Antibacterial spectrum : Cefalexin kills gram-positive and some gram-negative bacteria. The first-generation cephalosporins are resistant to the staphylococcal penicillinase (that is, they cover MSSA) and also have activity against Proteus mirabilis, E. coli, and K. pneumoniae. Cefalexin is not effective against infections caused by methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus, or Pseudomonas.
Therapeutic uses : Cephalexin has following uses :
- Used as alternatives to PnG; particularly in allergic patients (but not who had anaphylactic reaction).
- Used to treat Penicillinase producing staphylococcal infections.
- Used to treat Respiratory Tract Infections, Otitis Media, Skin and Skin Structure Infections, Bone Infections, Genitourinary Tract Infections caused by susceptible bacteria.
- It may also be used for certain types of pneumonia, strep throat, and to prevent bacterial endocarditis.
Mechanism of action : Cephalosporins cause inhibition of bacterial cell wall synthesis. i.e. they have the same mechanism of action as penicillin. However, they bind to different proteins than those which bind penicillins.
Side effects : Cephalosporins are generally well tolerated, but are more toxic than penicillin. Cephalexin may exhibit following side effects :
- Hypersensitivity reactions caused by cephalosporins are similar to penicillin, but incidence is lower. Rashes are the most frequent manifestation, but anaphylaxis, angioedema, asthma and urticaria have also occurred. About 10% patients allergic to penicillin show cross reactivity with cephalosporins. Those with a history of immediate type of reactions to penicillin should better not be given a cephalosporin. Skin tests for sensitivity to cephalosporins are unreliable.
- A positive Coombs’ test occurs in many, but haemolysis is rare.
- Diarrhea, nausea, vomiting,
- Seizure Potential,
- Effect on Prothrombin Activity,
- Pseudomembranous colitis and Clostridium difficile have been reported with use of cefalexin.
Drug Interactions : Cefalexin interacts with following drugs :
- Metformin : Increased plasma metformin concentrations and decreased renal clearance of metformin.
- Probenecid : Renal excretion of cefalexin is delayed.
Contraindications :
- Contraindicated in patients with known hypersensitivity to Cephalexin or other members of the cephalosporin class of antibacterial drugs.
For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.
