Keflex vs. Clindamycin

See how Keflex and Clindamycin compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Keflex is a first-generation cephalosporin best suited for common infections like skin, urinary tract, and respiratory infections, while clindamycin covers anaerobic infections and penicillin-allergic cases.

  • Clindamycin carries a boxed warning for C. difficile-associated diarrhea and colitis, a risk that is not called out with a boxed warning on Keflex's label.

  • Keflex needs a lower dose in people with reduced kidney function, while clindamycin is cleared mainly by the liver and does not require renal dose changes.

Keflex vs. Clindamycin Drug Summary

Keflex

Keflex (cephalexin) is a first-generation cephalosporin antibiotic used to treat infections such as skin, respiratory tract, ear, bone, and urinary tract infections. It comes as an oral capsule, tablet, or liquid, usually taken every 6 to 12 hours depending on the infection.

Clindamycin

Clindamycin is a lincosamide antibiotic used for serious anaerobic, skin, bone, and abdominal infections, and often chosen for people who cannot take penicillin-based drugs. It is available as an oral capsule, IV or IM injection, and topical or vaginal formulation, with oral doses typically taken every 6 hours.

Keflex vs. Clindamycin Side Effects

Keflex

Most common
Vomiting (rate not quantified in current label)
Abdominal pain (rate not quantified in current label)
Nausea (rate not quantified in current label)
Diarrhea (rate not quantified in current label)

Clindamycin

Most common
Vomiting (not specified as % in label, common)
Abdominal pain (not specified as % in label, common)
Nausea (not specified as % in label, common)
Diarrhea (not specified as % in label, common)

Keflex vs. Clindamycin Dosage

Keflex

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 25-50 mg/kg/day divided At the start
Maximum dose up to 4 g/day divided If needed
Dose changes 3 increases As tolerated

Clindamycin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 150 mg every 6 hours At the start
Maximum dose up to 4800 mg/day IV If needed
Dose changes 6 increases As tolerated

Keflex vs. Clindamycin Indications

Keflex

Keflex is FDA-approved for a range of common bacterial infections caused by susceptible organisms, including respiratory, ear, skin, bone, and urinary tract infections. It is sometimes used off-label to help prevent infection after certain surgical procedures.

  • Respiratory tract infections

  • Otitis media

  • Skin and skin structure infections

  • Bone infections

  • Genitourinary tract infections

Clindamycin

Clindamycin is FDA-approved for serious infections caused by anaerobic bacteria as well as certain streptococcal, staphylococcal, and pneumococcal infections, including skin, bone, and abdominal infections. Off-label, it is used for toxoplasmosis, malaria, and as a dental or surgical antibiotic in penicillin-allergic patients.

  • Serious anaerobic bacterial infections

  • Skin and skin structure infections

  • Bone and joint infections

  • Intra-abdominal infections

  • Gynecological infections

Keflex vs. Clindamycin Pros and Cons

Keflex

Keflex has decades of use as a first-line option for common infections and does not carry a boxed warning for C. difficile colitis, though the risk still exists. Its clearance depends on the kidneys, so people with reduced kidney function need a lower dose to avoid seizure risk.

Pros

  • Not associated with a boxed C. diff warning

  • Long-standing safety record after decades of use

  • Simple dosing schedule (every 6 to 12 hours)

  • Effective for common outpatient infections like UTIs and skin infections

Cons

  • Not effective against anaerobic bacteria

  • Requires dose adjustment in kidney impairment (seizure risk)

  • Cross-reactivity risk in penicillin-allergic patients

Clindamycin

Clindamycin reaches anaerobic bacteria that Keflex does not cover and offers oral, IV, topical, and vaginal formulations for different types of infections. It carries a boxed warning for C. difficile-associated diarrhea and colitis, a risk described more seriously than on Keflex's label.

Pros

  • Covers anaerobic bacteria Keflex does not treat

  • Available in oral, IV, topical, and vaginal forms

  • Preferred option for penicillin-allergic patients

  • No renal dose adjustment needed (hepatic clearance)

Cons

  • Boxed warning for C. difficile-associated colitis

  • Oral capsules can cause esophagitis if not taken with fluids

  • Should not be combined with erythromycin (antagonism)

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