Cephalexin
Pronunciation: (sef-a-LEX-in).
- Generic name
- cephalexin
- Brand names
- Cephalexin AN, Lexin, Cefalexin Sandoz, Apo-Cephalex, Novo-Lexin, Cephalexin Mylan
- Drug class
- First-generation cephalosporin
Availability and supply rules vary by country
Trade names by country: Canada
Australia: · Full directory
What cephalexin is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how cephalexin works
Cephalexin is a first-generation cephalosporin antibiotic. It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. It is bactericidal and primarily effective against Gram-positive bacteria and some Gram-negative organisms. (1) (2)
What cephalexin is used for
Bacterial infections
Bacterial infections (2)
Skin infections
Skin infections (2)
Respiratory tract infections
Respiratory tract infections (2)
Before taking cephalexin
Do not take / not appropriate for
- Contraindicated in patients with known hypersensitivity to cephalexin, other cephalosporins, or severe penicillin allergy due to cross-reactivity. (Contraindication) (2)
Tell your clinician about
(2)How to take cephalexin
- General Instructions: Take cephalexin exactly as prescribed by your healthcare provider. Do not skip doses and complete the full course, even if you feel better.. Adult Dosing: Typical adult dose is 250 mg to 500 mg every 6 to 12 hours, depending on the infection type and severity. Duration is usually 7 to 14 days.. Pediatric Dosing: Children are usually dosed based on body weight (25-50 mg/kg/day in divided doses). Follow your pediatrician's instructions closely.. Administration: Cephalexin can be taken with or without food. Swallow tablets or capsules whole with a glass of water. Shake oral suspension well before use.. When To Stop: Do not stop taking cephalexin early, even if symptoms improve. Only stop if directed by your healthcare provider or if you experience a serious allergic reaction.. Storage: Store capsules and tablets at controlled room temperature, 20°C to 25°C (68°F to 77°F), in a tight, light-resistant container, away from moisture and heat. Oral suspension should be refrigerated after mixing and discarded after 14 days.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2)
Missed dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose—do not double up. Resume your regular schedule.
Overdose
In case of overdose, seek emergency medical attention or contact a poison control center immediately. Symptoms may include severe nausea, vomiting, diarrhea, blood in urine, or seizures. (2)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Diarrhea
Incidence: Reported in the clinician-authored database; frequency not established
Nausea
Incidence: Reported in the clinician-authored database; frequency not established
Vomiting
Incidence: Reported in the clinician-authored database; frequency not established
Abdominal pain
Incidence: Reported in the clinician-authored database; frequency not established
Rash
Incidence: Reported in the clinician-authored database; frequency not established
Allergic reactions (hives, itching, swelling)
Incidence: Reported in the clinician-authored database; frequency not established
Pseudomembranous colitis
Incidence: Reported in the clinician-authored database; frequency not established
Severe, watery, or bloody diarrhea (possible C. difficile-associated colitis), signs of a serious allergic reaction (hives, facial/throat swelling, difficulty breathing), or a widespread rash.
(1)Serious warnings
Serious allergic reactions can occur, especially in those with penicillin allergies — serious
Symptoms: Serious allergic reactions can occur, especially in those with penicillin allergies. Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea. Use with caution in patients with kidney impairment—dose adjustment may be necessary. May cause false-positive results in certain urine glucose tests. Inform your doctor of all medications and supplements you are taking to avoid interactions.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Contraindications recorded in the clinician database — serious
Symptoms: Contraindications recorded in the clinician database: Contraindicated in patients with known hypersensitivity to cephalexin, other cephalosporins, or severe penicillin allergy due to cross-reactivity. Use with caution in patients with renal impairment (dose adjustment required), history of gastrointestinal disease (especially colitis), or those at risk for superinfection.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Cephalexin may interact with certain medications, including metformin (risk of increased metformin levels), probenecid (increases cephalexin levels), and live bacterial vaccines. It may also interfere with some urine glucose tests. Always inform your healthcare provider about all medicines and supplements you are taking. | (1) |
| Probenecid | Probenecid inhibits the renal excretion of cephalexin and can raise cephalexin blood levels; co-administration is generally not recommended. | (2) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Cephalexin is Pregnancy Category B. Animal reproduction studies at up to 1.5 times the maximum human dose showed no evidence of impaired fertility or fetal harm, but there are no adequate, well-controlled studies in pregnant women, so safety in human pregnancy has not been formally established. Use during pregnancy only if clearly needed, and discuss with the treating clinician. (2)
Breastfeeding
Cephalexin passes into breast milk (peak concentration around 4 mcg/mL about 4 hours after a 500 mg dose, becoming undetectable by about 8 hours). Caution should be exercised when cephalexin is given to a nursing woman; discuss feeding options with the treating clinician. (2)
Children
Frequency: Every 6 to 12 hours.. Weight Based: 25 to 50 mg/kg/day divided into doses every 6 to 12 hours.. Max Daily Dose: 4 g. Max Single Dose: 500 mg. Age Restrictions: Not recommended for pediatric use under 1 year of age. (2)
Renal_impairment
Cephalexin should be used with caution in patients with markedly impaired renal function; the label recommends careful clinical observation and laboratory monitoring, since a safe dosage may be lower than the usual recommended dose. Dosage adjustment is required for severe or end-stage renal disease (creatinine clearance below 30 mL/min); the treating clinician determines the adjusted regimen. (2)
Hepatic_impairment
Cephalexin should be used with caution in patients with markedly impaired renal function; the label recommends careful clinical observation and laboratory monitoring, since a safe dosage may be lower than the usual recommended dose. Dosage adjustment is required for severe or end-stage renal disease (creatinine clearance below 30 mL/min); the treating clinician determines the adjusted regimen. (2)
Monitoring
(2)Storage
Store capsules and tablets at controlled room temperature, 20°C to 25°C (68°F to 77°F), in a tight, light-resistant container, away from moisture and heat. After mixing, oral suspension should be stored in a refrigerator and may be kept for up to 14 days without significant loss of potency.
Study the drug class: Cephalosporins
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Bacterial infections
Dose summary: 250 mg to 500 mg every 6 hours for mild to moderate infections; 500 mg to 1 g every 12 hours for more severe infections.
Renal context: No formal creatinine-clearance dosing table in the label; use with caution and careful clinical observation/laboratory monitoring in markedly impaired renal function, since a safe dose may be lower than usual. Dosage adjustment is required for severe/end-stage renal disease (CrCl below 30 mL/min). (1) (2)
Frequently asked questions
What infections does cephalexin treat?
Cephalexin treats bacterial infections such as skin infections, respiratory tract infections, urinary tract infections, bone infections, and ear infections.
Can I take cephalexin if I am allergic to penicillin?
Some people allergic to penicillin may also react to cephalexin. Inform your doctor about any allergies before starting cephalexin.
Should I take cephalexin with food?
Cephalexin can be taken with or without food. Taking it with food may help reduce stomach upset.
What should I do if I develop diarrhea while taking cephalexin?
Mild diarrhea is common, but severe, watery, or bloody diarrhea may indicate a serious infection (C. difficile). Contact your doctor if this occurs.
Is cephalexin safe during pregnancy and breastfeeding?
Cephalexin is generally considered safe during pregnancy and breastfeeding, but always consult your healthcare provider before use.
How long does it take for cephalexin to work?
Most people start to feel better within a few days. However, complete the full course as prescribed to ensure the infection is fully treated.
Can cephalexin treat viral infections like the flu?
No, cephalexin is only effective against bacterial infections and will not treat viral illnesses such as the flu or common cold.
What happens if I take too much Cephalexin?
Taking too much Cephalexin can lead to symptoms like nausea, vomiting, diarrhea, and stomach pain. In severe cases, it may cause kidney problems or seizures. If you suspect an overdose, it is crucial to seek emergency medical attention immediately. Do not attempt to induce vomiting or self-treat.
Can I drink alcohol while taking Cephalexin?
While Cephalexin itself does not typically have a direct interaction with alcohol, consuming alcohol while on antibiotics can worsen common side effects like nausea, vomiting, and dizziness. Alcohol can also weaken your immune system, potentially hindering your recovery from the infection. It's generally best to avoid alcohol during antibiotic treatment.
Is Cephalexin safe during pregnancy?
Cephalexin is classified as Pregnancy Category B, meaning animal reproduction studies have not demonstrated a fetal risk, but there are no adequate and well-controlled studies in pregnant women. Therefore, it is essential to consult your doctor before taking Cephalexin if you are pregnant or planning to become pregnant. Your healthcare provider will weigh the potential benefits against any risks.
What is the mechanism of action of cephalexin?
Cephalexin is a first-generation cephalosporin antibiotic. It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. It is bactericidal and primarily effective against Gram-positive bacteria and some Gram-negative organisms. (1) (2)
What is the generic name of Cephalexin?
The generic name is cephalexin. It is sold under brand names including Cephalexin AN, Lexin, Cefalexin Sandoz, Apo-Cephalex, Novo-Lexin, Cephalexin Mylan.
What class of drug is cephalexin?
Cephalexin is classed as: First-generation cephalosporin.
References
- Cephalexin Clinician-authored Medicine Record (Internal Database)MedGuideGlobal · Global · accessed 2026-08-06 · source 1
- Cephalexin capsules and oral suspension prescribing informationU.S. Food and Drug Administration · United States · accessed 2026-08-06 · source 2
- CEPHALEXIN CAPSULE [PD-RX PHARMACEUTICALS, INC.] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 3
- Cephalexin — FDA approval record (Drugs@FDA ANDA065253)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 4
- cephalexin — RxNorm normalized drug concept (RXCUI 215948)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 5
Brand names by country
Single-ingredient cephalexin names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
Canada
- KEFLEX
- APO-CEPHALEX
- PMS-CEPHALEXIN 125 - SUS
- PMS-CEPHALEXIN 250 - SUS
- DOM-CEPHALEXIN 125 - SUS
- DOM-CEPHALEXIN 250 - SUS