First-generation cephalosporin indicated for respiratory tract infections (Streptococcus pneumoniae and S. pyogenes), otitis media, skin and skin structure infections, and urinary tract and bone infections due to susceptible organisms.
Also known as: Cefalexina, Keflex
DailyMed approved label (Cephalexin Capsule; setID b73593ce-0b1f-4371-bae1-140742de3b42).
DailyMed approved label (Cephalexin Capsule; setID b73593ce-0b1f-4371-bae1-140742de3b42).
Cephalexin + probenecid: probenecid inhibits cephalexin tubular secretion — combination not recommended.
The FDA cephalexin label explicitly documents: "Probenecid - The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended" (section 7.2). Probenecid blocks the renal tubular secretion of beta-lactams, raising and prolonging serum cephalexin concentrations — historically used to prolong penicillin levels, but increasing the risk of dose-dependent adverse effects (neurotoxicity, diarrhoea, skin reactions). In the elderly and renally impaired, the risk of neurotoxicity (confusion, myoclonus) is higher. The practical guidance is to avoid the combination; if probenecid is essential (e.g., as a uricosuric in a patient with infection), consider reducing the cephalexin dose or extending the interval and monitor for signs of toxicity.
Cephalexin + probenecid: probenecid inhibits cephalexin tubular secretion — combination not recommended.
The FDA cephalexin label documents: "Probenecid - The renal excretion of cephalexin is inhibited by probenecid. Co-administration of probenecid with cephalexin is not recommended" (7.2). Probenecid blocks the renal tubular secretion of beta-lactams, raising and prolonging serum cephalexin concentrations (risk of dose-dependent toxicity/adverse effects).
Monitor for signs of toxicity (neurotoxicity, diarrhoea, skin reactions) if the combination is used.
Neurotoxicity (confusion, myoclonus) or increased adverse effects with the combination.
Avoid the combination; if probenecid is essential, consider reducing the cephalexin dose or extending the interval.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label (PREFERRED PHARMACEUTICALS), section 7.2: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=553485f8-890d-4929-a6bb-905221cf411d ; approved Probenecid label (MARLEX): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5d552de5-2d18-4464-bcaf-0311fa3f080d
Cephalexin + metformin: cephalexin increases metformin concentrations — monitor for hypoglycaemia.
The FDA cephalexin label documents: "Metformin: increased metformin concentrations. Monitor for hypoglycemia" (section 7.1). Cephalexin competes with metformin for renal tubular secretion via the OCT2 transporter, reducing metformin elimination and increasing its systemic exposure. In the diabetic patient on metformin, cephalexin antibiotic therapy may translate into higher antidiabetic levels and increased risk of hypoglycaemia — especially in patients with borderline renal function or prolonged fasting. The practical guidance is to warn about hypoglycaemia symptoms (sweating, tremor, confusion) and consider more frequent glucose monitoring during antibiotic therapy.
Cephalexin + metformin: cephalexin increases metformin concentrations — monitor for hypoglycaemia in the diabetic patient.
The FDA cephalexin label documents: "Metformin: increased metformin concentrations. Monitor for hypoglycemia" (7.1). Cephalexin competes with metformin for renal tubular secretion (OCT2 transporter), reducing its elimination and increasing metformin systemic exposure.
Monitor blood glucose and hypoglycaemia symptoms during the combination.
Symptomatic hypoglycaemia (sweating, tremor, confusion) in a diabetic patient taking cephalexin.
Monitor for signs of hypoglycaemia in diabetic patients during cephalexin antibiotic therapy.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label (section 7.1): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=553485f8-890d-4929-a6bb-905221cf411d ; approved Metformin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34496b43-05a2-45fb-a769-52b12e099341
Alcohol may worsen the gastrointestinal effects of cephalexin; limit intake.
Limit alcohol intake during treatment.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b73593ce-0b1f-4371-bae1-140742de3b42
Cephalexin can be taken with or without food; taking with food reduces gastrointestinal discomfort.
Take with food if gastric discomfort occurs.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b73593ce-0b1f-4371-bae1-140742de3b42
Cephalexin is renally excreted; in renal impairment the dose must be adjusted.
Adjust the dose to renal function.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b73593ce-0b1f-4371-bae1-140742de3b42
Cephalexin is a cephalosporin; it is contraindicated in prior cephalosporin allergy and requires caution in severe penicillin allergy.
Contraindicated in cephalosporin allergy; caution in severe penicillin allergy.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b73593ce-0b1f-4371-bae1-140742de3b42
Cephalosporins, including cephalexin, are generally safe in pregnancy when indicated.
May be used in pregnancy when indicated, at the usual doses.
Excreted into breast milk in small amounts; compatible with breastfeeding.
No specific additional contraception.
DailyMed/FDA (NIH/NLM) — approved Cephalexin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b73593ce-0b1f-4371-bae1-140742de3b42
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Bactericidal antibiotic that inhibits bacterial cell-wall synthesis (first-generation cephalosporin). The pharmacodynamic parameter predictive of efficacy is the time during which the free concentration exceeds the MIC of the organism.
Inhibition of cell-wall synthesis by binding to penicillin-binding proteins (PBPs), with bacterial lysis during active multiplication.
Acid stable (may be given without regard to meals); peak serum levels of ~9, 18 and 32 mcg/mL 1 hour after 250, 500 and 1000 mg doses. Plasma protein binding 10–15%.
Excreted in urine by glomerular filtration and tubular secretion; over 90% of the dose is eliminated unchanged in urine within 8 hours.
Elimination half-life ~1 h in patients with normal renal function (serum levels remain detectable up to 6 hours after dosing).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
