Oral Equivalent to Keflex (Cephalexin)
Keflex (cephalexin) is itself an oral medication, so the oral equivalent to Keflex is simply cephalexin. Cephalexin is a first-generation cephalosporin antibiotic available in oral formulations including capsules, tablets, and suspension 1.
Dosage Forms and Administration
- Capsules: Available in 250 mg and 500 mg strengths
- Tablets: Available in 250 mg and 500 mg strengths
- Oral suspension: Available in 125 mg/5mL and 250 mg/5mL concentrations
Standard Dosing for Adults
- For skin and soft tissue infections: 500 mg four times daily 2
- For severe infections: Higher doses up to 1 gram four times daily may be indicated 2
- For typical cellulitis: 5-day course is as effective as a 10-day course if clinical improvement occurs by day 5 3
Pharmacological Properties
- Cephalexin is not absorbed from the stomach but is rapidly and completely absorbed in the upper intestine 4
- It is primarily excreted unchanged through the kidneys with 70-100% of the dose found in urine within 6-8 hours 4
- Dose adjustment is required for patients with creatinine clearance less than 30 mL/min 4
Clinical Applications
Cephalexin is effective for:
- Skin and soft tissue infections (particularly those caused by streptococci and MSSA) 3, 5
- Upper respiratory tract infections 6
- Streptococcal pharyngitis (as an alternative in penicillin-allergic patients) 3
Alternative First-Generation Cephalosporins
- Cefadroxil: Has similar in vitro activity against MSSA as cephalexin (MIC50 of 2 μg/mL and MIC90 of 4 μg/mL for both) 7
- Cefadroxil advantage: Longer half-life allowing for less frequent dosing compared to cephalexin 7
Important Considerations
- Cephalexin is ineffective against MRSA, so coverage for MRSA should be considered in certain situations (e.g., purulent drainage, concurrent MRSA infection elsewhere) 3
- Up to 10% of penicillin-allergic persons may also be allergic to cephalosporins, and cephalexin should not be used in patients with immediate (anaphylactic-type) hypersensitivity to penicillin 3
- Narrow-spectrum cephalosporins like cephalexin are preferred over broad-spectrum cephalosporins (cefaclor, cefuroxime, cefixime, cefdinir, cefpodoxime) to reduce selection of antibiotic-resistant flora 3
Comparison to Other Oral Cephalosporins
- Cefaclor has poor activity against H. influenzae and no activity against drug-resistant S. pneumoniae 3
- Cefprozil has similar activity against S. pneumoniae as cephalexin but is less active against H. influenzae 3
- Cefpodoxime and cefixime have greater activity against H. influenzae but are broader spectrum and more expensive 3, 8
In summary, cephalexin (Keflex) is already an oral medication, and generic cephalexin is the oral equivalent to the brand name Keflex. For patients requiring a first-generation cephalosporin with less frequent dosing, cefadroxil may be considered as an alternative with similar antimicrobial activity.