Amoxicillin vs. Bactrim
See how Amoxicillin and Bactrim compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Amoxicillin, a penicillin-class antibiotic, treats ear, throat, and respiratory infections, while Bactrim, a sulfa combination, treats UTIs, PCP pneumonia, and traveler's diarrhea.
Both are inexpensive generic antibiotics, but Bactrim carries added warnings for severe skin reactions, hemolytic anemia in G6PD deficiency, and use in young infants.
Amoxicillin is often chosen first for common childhood and respiratory infections, while Bactrim is used when broader gram-negative coverage or PCP prevention is needed.
Amoxicillin vs. Bactrim Drug Summary
Amoxicillin
Amoxicillin is an aminopenicillin antibiotic used to treat infections of the ear, nose, throat, lungs, skin, and urinary tract, along with H. pylori and gonorrhea as part of combination therapy. It has been available since 1974 and is typically taken as a tablet, capsule, chewable, or oral suspension every 8 to 12 hours.
Bactrim
Bactrim combines sulfamethoxazole and trimethoprim to block two steps in bacterial folate production, treating conditions such as urinary tract infections, Pneumocystis pneumonia, shigellosis, and traveler's diarrhea. Approved since 1973, it is taken orally or by injection, usually every 12 hours depending on the infection.
Amoxicillin vs. Bactrim Side Effects
Amoxicillin
Bactrim
Amoxicillin vs. Bactrim Dosage
Amoxicillin
Bactrim
| 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 | 800 mg/160 mg every 12h | At the start |
| Maximum dose | 8-10 mg/kg/day div q6-12h | 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 |
Bactrim
| STAGE | DOSE | WHEN |
| Starting dose | 800 mg/160 mg every 12h | At the start |
| Maximum dose | 8-10 mg/kg/day div q6-12h | If needed |
| Dose changes | 3 increases | As tolerated |
Amoxicillin vs. Bactrim Indications
Amoxicillin
Amoxicillin is FDA-approved for a wide range of common bacterial infections, including those of the ear, nose, throat, and lower respiratory tract. It also treats skin infections and uncomplicated urinary tract infections, and it is used with other drugs to eradicate H. pylori or treat gonorrhea.
Ear, nose, and throat infections
Lower respiratory tract infections
Skin and skin structure infections
Urinary tract infections
H. pylori eradication (combination therapy)
Bactrim
Bactrim is FDA-approved for urinary tract infections, Pneumocystis jirovecii pneumonia, shigellosis, and acute otitis media in children. It also treats bronchitis flare-ups in adults and traveler's diarrhea, and it is commonly used off-label for MRSA skin infections.
Urinary tract infections
Pneumocystis pneumonia (treatment and prevention)
Shigellosis
Acute otitis media in children
MRSA skin infections (off-label use)
Amoxicillin vs. Bactrim Pros and Cons
Amoxicillin
Amoxicillin has a long safety record and works well for common infections in children and adults, with a relatively low rate of serious side effects. It is not effective against many resistant bacteria and can trigger a distinctive rash in people with mononucleosis.
Pros
Long-standing safety record since 1974
Well tolerated in children and during pregnancy
Effective first-line option for ENT and respiratory infections
Fewer severe cutaneous reaction warnings than Bactrim
Cons
Not effective against MRSA or many resistant bacteria
Can cause severe rash if given during mononucleosis
Cross-reactivity risk in patients with penicillin allergy
Not effective against Pneumocystis pneumonia
Bactrim
Bactrim offers broader coverage against resistant bacteria and is the standard treatment for Pneumocystis pneumonia. It carries more serious warnings, including severe skin reactions, hemolytic anemia risk, and contraindications in pregnancy and early infancy.
Pros
Effective for Pneumocystis pneumonia treatment and prevention
Covers MRSA and many resistant gram-negative bacteria
Useful for traveler's diarrhea and shigellosis
Broader spectrum against resistant organisms
Cons
Contraindicated in infants under two months old
Should be avoided during pregnancy and breastfeeding
Higher risk of severe skin reactions like Stevens-Johnson syndrome
Risk of hemolytic anemia in G6PD-deficient patients
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