Keflex (Cephalexin) is NOT Recommended for Eye Infections
Cephalexin should not be used for bacterial eye infections (conjunctivitis) as it lacks adequate coverage against the most common ocular pathogens and does not achieve sufficient concentrations in ocular tissues.
Why Cephalexin is Inappropriate for Eye Infections
Inadequate Pathogen Coverage
- Cephalexin has poor activity against Haemophilus influenzae and Moraxella catarrhalis, which are among the most common bacterial causes of conjunctivitis 1
- A controlled trial demonstrated that oral cefixime (a related cephalosporin with better coverage) failed to effectively eradicate conjunctival colonization with respiratory pathogens, with a 37.5% bacteriologic failure rate 2
- Cephalexin is completely ineffective against Pseudomonas aeruginosa, an important pathogen in contact lens-related eye infections 1
Poor Ocular Tissue Penetration
- Cephalexin does not penetrate into host tissue cells and does not achieve therapeutic concentrations in the aqueous humor or ocular tissues 3
- The drug is designed for systemic infections where it distributes to most tissues, but the eye is specifically excluded from adequate penetration 3
Clinical Evidence Against Systemic Therapy
- Systemic antibiotics do not provide superior outcomes compared to topical therapy for bacterial conjunctivitis 2
- In a randomized controlled trial, oral cefixime was no more effective than topical polymyxin-bacitracin for clinical or bacteriologic cure of bacterial conjunctivitis 2
Appropriate Treatment Approach
For Bacterial Conjunctivitis
- Use topical antibiotic therapy as first-line treatment (e.g., polymyxin-bacitracin, fluoroquinolone eye drops, or other ophthalmic preparations) 2
- Topical therapy achieves high local concentrations directly at the site of infection 2
When Cephalexin IS Appropriate
Cephalexin is indicated for:
- Skin and soft tissue infections at 500 mg four times daily 4, 5
- Respiratory tract infections (though limited by poor H. influenzae coverage) 1
- Genitourinary tract infections 3
Critical Pitfall to Avoid
Do not prescribe oral cephalexin for eye infections thinking it will provide systemic coverage—it will not adequately treat the infection and may delay appropriate topical therapy, potentially leading to complications 1, 2.