Bactrim vs. Cephalexin
See how Bactrim and Cephalexin compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Bactrim and cephalexin are both oral antibiotics, but they come from different drug classes and target different types of bacteria.
Bactrim is often chosen for urinary tract infections, Pneumocystis pneumonia, and off-label MRSA treatment, while cephalexin is a go-to for strep-related skin, respiratory, and bone infections.
Cephalexin is generally viewed as gentler and safer in pregnancy, while Bactrim carries extra warnings for G6PD deficiency, folate deficiency, and pregnancy.
Bactrim vs. Cephalexin Drug Summary
Bactrim
Bactrim combines sulfamethoxazole and trimethoprim, two drugs that block sequential steps in bacterial folate production. It's FDA approved for urinary tract infections, Pneumocystis pneumonia, shigellosis, traveler's diarrhea, and certain ear and bronchial infections. It's available as a tablet, oral suspension, or IV injection, usually dosed twice a day.
Cephalexin
Cephalexin is a first-generation cephalosporin antibiotic that stops bacteria from forming their cell walls. It's FDA approved for respiratory, skin, bone, and urinary tract infections caused by susceptible staph and strep bacteria. It's available as a capsule, tablet, or oral suspension, typically dosed every 6 to 12 hours.
Bactrim vs. Cephalexin Side Effects
Bactrim
Cephalexin
Bactrim vs. Cephalexin Dosage
Bactrim
Cephalexin
| STAGE | DOSE | WHEN |
| Starting dose | 800 mg/160 mg every 12h | At the start |
| Maximum dose | 8-10 mg/kg/day q6-12h | If needed |
| Dose changes | 3 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 25-50 mg/kg/day divided | At the start |
| Maximum dose | 1 to 4 g/day divided | If needed |
| Dose changes | 4 increases | As tolerated |
Bactrim
| STAGE | DOSE | WHEN |
| Starting dose | 800 mg/160 mg every 12h | At the start |
| Maximum dose | 8-10 mg/kg/day q6-12h | If needed |
| Dose changes | 3 increases | As tolerated |
Cephalexin
| STAGE | DOSE | WHEN |
| Starting dose | 25-50 mg/kg/day divided | At the start |
| Maximum dose | 1 to 4 g/day divided | If needed |
| Dose changes | 4 increases | As tolerated |
Bactrim vs. Cephalexin Indications
Bactrim
Bactrim is FDA approved to treat urinary tract infections, Pneumocystis jirovecii pneumonia, shigellosis, traveler's diarrhea in adults, acute otitis media in children, and bronchitis flare-ups. Doctors also prescribe it off-label for MRSA skin infections and Stenotrophomonas maltophilia. It is not effective against strep throat, since group A strep resists sulfonamides.
Urinary tract infections
Pneumocystis pneumonia (treatment and prevention)
Traveler's diarrhea in adults
Acute otitis media in children
Off-label: MRSA skin infections
Cephalexin
Cephalexin is FDA approved for respiratory tract, skin, bone, and urinary tract infections caused by susceptible staph and strep bacteria. It's also used for otitis media in children caused by susceptible organisms. Off-label, it's sometimes used as an adjunct for acne or to prevent surgical site infections.
Skin and skin structure infections
Respiratory tract infections
Bone infections
Urinary tract infections including prostatitis
Off-label: acne adjunct therapy
Bactrim vs. Cephalexin Pros and Cons
Bactrim
Bactrim covers a broad range of bacteria, including MRSA when used off-label, and is dosed just twice a day for most infections. It requires caution in people with G6PD deficiency, kidney problems, or folate deficiency, and should be avoided during pregnancy.
Pros
Effective against MRSA (off-label use)
Only taken twice daily for most infections
Covers gram-negative bacteria cephalexin does not treat
IV form available for hospitalized patients
Cons
Higher risk of severe skin reactions like Stevens-Johnson syndrome
Contraindicated in G6PD deficiency and folate deficiency anemia
Not safe during pregnancy or for infants under 2 months
Not effective against strep throat
Cephalexin
Cephalexin has a long safety record and is generally considered one of the gentler antibiotic options, including during pregnancy. It needs more frequent dosing for some infections and does not cover MRSA or other resistant staph.
Pros
Considered safer to use during pregnancy
Well tolerated with a long history of safe use
Effective first-line option for strep throat and skin infections
Available as capsule, tablet, or suspension for flexible dosing
Cons
Requires dosing up to 4 times daily for some infections
Not effective against MRSA or other resistant staph
Dose must be adjusted for significant kidney impairment
Narrower spectrum against gram-negative bacteria
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