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

Most common
Vomiting (rate not quantified in label)
Nausea (rate not quantified in label)
Anorexia (rate not quantified in label)
Rash (rate not quantified in label)

Cephalexin

Most common
Vomiting (rate not specified in FDA label)
Nausea (rate not specified in FDA label)
Diarrhea (rate not specified in FDA label)
Dyspepsia (rate not specified in FDA label)

Bactrim vs. Cephalexin Dosage

Bactrim

Dosage
Dosage Table
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

Dosage
Dosage Table
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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