Another Name for Keflex
Cephalexin is another name for Keflex. 1
Understanding Cephalexin/Keflex
Cephalexin is a semisynthetic first-generation cephalosporin antibiotic that is available for oral administration. It is chemically described as 7-(D-α-amino-α-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid, monohydrate 1. The drug is marketed under the brand name Keflex, though it is also widely available as generic cephalexin.
Chemical Structure and Properties
- Cephalexin has a molecular weight of 365.41 1
- It is a zwitterion (contains both basic and acidic groups) 1
- The isoelectric point in water is approximately 4.5 to 5 1
- Available as a monohydrate in crystalline form 1
- Has relatively low solubility in water at room temperature 1
Formulations
Cephalexin/Keflex is available in several formulations:
- Capsules: 250 mg and 500 mg 1
- Oral suspension: 125 mg/5 mL and 250 mg/5 mL 1
- Tablets: 250 mg and 500 mg 1
Clinical Applications
Cephalexin is widely used in clinical practice for various infections due to its broad spectrum of activity against many common pathogens. It is particularly effective against:
- Upper and lower respiratory tract infections 2
- Skin and soft tissue infections 3
- Urinary tract infections 4, 5
- Otitis media (except for H. influenzae infections) 2
Antimicrobial Spectrum
Cephalexin is active against:
- Gram-positive cocci, including penicillinase-producing staphylococci 6
- Many gram-negative organisms 6
- It has limited activity against H. influenzae 2
Important Considerations
Cross-Reactivity with Penicillins
First-generation cephalosporins like cephalexin may have cross-reactivity with penicillins in allergic patients. According to guidelines, cephalosporins should not be administered to patients with a history of anaphylaxis, angioedema, or urticaria after treatment with any form of penicillin, including ampicillin or amoxicillin 3.
Ineffectiveness for Certain Conditions
It's important to note that first-generation cephalosporins such as cephalexin are ineffective for treatment of Lyme disease and should not be used for this purpose 3.
Dosing Considerations
- For adults, typical dosing is 1-2 g/day 2
- For children, dosing ranges from 20-100 mg/kg/day 2
- In patients with renal impairment (creatinine clearance <30 ml/min), dose reduction is necessary 7
- For urinary tract infections, a simplified twice-daily dosing regimen of 1g has shown similar efficacy to four-times-daily dosing 5
Side Effects
Cephalexin is generally well-tolerated with a low incidence of side effects 6. When adverse effects occur, they typically include:
- Gastrointestinal upsets
- Rash and urticaria
- These side effects are relatively infrequent and rarely require discontinuation of the drug 2
Cephalexin's stability and chemical configuration contribute to its very low incidence of allergic reactions compared to some other antibiotics 7.