Amoxicillin vs. Keflex
See how Amoxicillin and Keflex compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Amoxicillin and Keflex (cephalexin) are both oral antibiotics used to treat many of the same bacterial infections, including ear, skin, and urinary tract infections.
Amoxicillin is usually dosed every 8 to 12 hours, while standard Keflex dosing is every 6 hours, which can make Amoxicillin easier to fit into a daily routine.
Amoxicillin generally costs less than Keflex, but Keflex is a useful option for patients with a penicillin allergy who are not also allergic to cephalosporins.
Amoxicillin vs. Keflex Drug Summary
Amoxicillin
Amoxicillin is an aminopenicillin antibiotic used to treat infections of the ear, nose, throat, lungs, skin, and urinary tract, as well as gonorrhea and, in combination regimens, H. pylori. It's taken orally as a capsule, tablet, chewable tablet, or liquid suspension, usually two to three times a day.
Keflex
Keflex (cephalexin) is a first-generation cephalosporin antibiotic used to treat infections of the respiratory tract, ears, skin, bones, and urinary system. It's taken orally as a capsule, tablet, or liquid suspension, typically every 6 to 12 hours depending on how severe the infection is.
Amoxicillin vs. Keflex Side Effects
Amoxicillin
Keflex
Amoxicillin vs. Keflex Dosage
Amoxicillin
Keflex
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg every 8 hours | At the start |
| Maximum dose | 1 g three times daily | If needed |
| Dose changes | 4 increases | As tolerated |
| 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 |
Amoxicillin
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg every 8 hours | At the start |
| Maximum dose | 1 g three times daily | If needed |
| Dose changes | 4 increases | As tolerated |
Keflex
| 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 |
Amoxicillin vs. Keflex Indications
Amoxicillin
Amoxicillin is FDA-approved for a wide range of common bacterial infections, from ear and sinus infections to urinary tract infections and gonorrhea. It's also used as part of combination therapy to eradicate H. pylori, the bacteria linked to stomach ulcers.
Ear, nose, and throat infections
Lower respiratory tract infections
Skin and skin structure infections
Urinary tract infections
Gonorrhea and H. pylori eradication (combination therapy)
Keflex
Keflex is FDA-approved for infections of the respiratory tract, skin, bones, and urinary system, and it's also used for middle ear infections. It's sometimes used off-label to help prevent infection during certain surgeries.
Respiratory tract infections
Middle ear infections (otitis media)
Skin and skin structure infections
Bone infections
Genitourinary tract infections
Amoxicillin vs. Keflex Pros and Cons
Amoxicillin
Amoxicillin has one of the broadest FDA-approved indication lists among oral antibiotics and is typically well tolerated with predictable, low side-effect rates. It's also one of the least expensive antibiotics available, though it's not an option for anyone with a penicillin allergy.
Pros
Approved for gonorrhea and H. pylori, unlike Keflex
Some regimens allow twice-daily dosing (every 12 hours)
Typically costs $11 to $25 per month, much less than Keflex
Long track record with well-quantified side effect rates
Cons
Not an option for patients with a penicillin allergy
Higher risk of rash if given during mono infection
Some regimens require dosing every 8 hours
Not effective against Pseudomonas or similar resistant bacteria
Keflex
Keflex offers an alternative for patients who can't take penicillins, as long as they don't also have a cephalosporin allergy. It's specifically approved for bone infections and is sometimes used off-label to help prevent surgical site infections.
Pros
Alternative for some patients with penicillin allergy
FDA-approved specifically for bone infections
Used off-label for surgical infection prevention
Higher max dose (up to 4 g/day) for severe infections
Cons
Typically costs $53 to $95 for a 20-capsule course
Standard dosing is every 6 hours, more frequent than Amoxicillin
Seizure risk if it accumulates in kidney impairment
Can raise metformin levels, requiring blood sugar monitoring
Common Symptoms and Related Diseases You Can Explore
Explore a range of common symptoms the Doctronic Symptom Checker can help you understand.