Macrobid vs. Trimethoprim
See how Macrobid and Trimethoprim compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Macrobid is taken twice daily for 7 days, while trimethoprim is taken once or twice daily for a 10-day course.
Macrobid should be avoided in people with reduced kidney function, while trimethoprim carries its own risks of high potassium and blood cell changes.
Trimethoprim contains no sulfonamide component, making it an option for people with sulfa allergies who cannot take combination antibiotics.
Macrobid vs. Trimethoprim Drug Summary
Macrobid
Macrobid (nitrofurantoin) is a urinary anti-infective that treats acute, uncomplicated UTIs caused by E. coli or S. saprophyticus. It is taken as a capsule twice a day for seven days and works almost entirely within the urinary tract, with little effect elsewhere in the body.
Trimethoprim
Trimethoprim is a urinary anti-infective that blocks bacterial folate production to treat acute, uncomplicated UTIs from E. coli and several other bacteria. It comes as a tablet taken once or twice daily for a 10-day course and lacks the sulfa component found in combination antibiotics.
Macrobid vs. Trimethoprim Side Effects
Macrobid
Trimethoprim
Macrobid vs. Trimethoprim Dosage
Macrobid
Trimethoprim
| STAGE | DOSE | WHEN |
| Starting dose | 100 mg every 12 hours | Days 1-7 |
| Maximum dose | 100 mg every 12 hours | Same as starting |
| Dose changes | None | Fixed dose |
| STAGE | DOSE | WHEN |
| Starting dose | 100 mg every 12 hours | Days 1-10 |
| Maximum dose | 200 mg once daily | Days 1-10 |
| Dose changes | 1 increase | As tolerated |
Macrobid
| STAGE | DOSE | WHEN |
| Starting dose | 100 mg every 12 hours | Days 1-7 |
| Maximum dose | 100 mg every 12 hours | Same as starting |
| Dose changes | None | Fixed dose |
Trimethoprim
| STAGE | DOSE | WHEN |
| Starting dose | 100 mg every 12 hours | Days 1-10 |
| Maximum dose | 200 mg once daily | Days 1-10 |
| Dose changes | 1 increase | As tolerated |
Macrobid vs. Trimethoprim Indications
Macrobid
Macrobid is FDA-approved for acute, uncomplicated urinary tract infections caused by E. coli or S. saprophyticus. It is also used off-label at low doses for long-term prevention of recurrent UTIs, though it is not approved for kidney infections or for use in children under 12.
Acute uncomplicated UTI (cystitis) from E. coli or S. saprophyticus
Off-label: long-term low-dose prophylaxis for recurrent UTIs
Not approved for pyelonephritis or kidney abscess
Not approved for children under 12 or infants under 1 month
Trimethoprim
Trimethoprim is FDA-approved for acute, uncomplicated UTIs caused by E. coli and several other bacteria, including Proteus and Klebsiella. It is also used off-label to prevent recurrent UTIs and, combined with dapsone, to prevent Pneumocystis pneumonia, though it is not approved for infants under 2 months.
Acute uncomplicated UTI from E. coli, Proteus, Klebsiella, and others
Off-label: prevention of recurrent UTIs
Off-label: PCP prophylaxis in combination with dapsone
Not approved for infants younger than 2 months
Macrobid vs. Trimethoprim Pros and Cons
Macrobid
Macrobid has remained reliably effective against E. coli despite decades of widespread use, largely because it concentrates in urine rather than the bloodstream. That same low systemic absorption limits its use to lower urinary tract infections and makes kidney function a key safety consideration.
Pros
Still reliably effective against E. coli after decades of use
Concentrates in urine, so it causes fewer systemic side effects
FDA-approved since 1990 with a long track record
Also used off-label for long-term UTI prevention
Cons
Contraindicated with reduced kidney function (CrCl under 60)
Risk of pulmonary toxicity, including fibrosis, with long-term use
Risk of liver toxicity, including hepatitis
Contraindicated in late pregnancy (38 to 42 weeks)
Trimethoprim
Trimethoprim works well against a slightly broader range of UTI-causing bacteria and offers a convenient once-daily dosing option. Because it blocks folate metabolism, it carries its own risks, including changes in blood potassium and blood cell counts that Macrobid does not share.
Pros
Covers a broader range of bacteria, including Proteus and Klebsiella
Available as a once-daily 200 mg dose
No sulfonamide component, an option for sulfa-allergic patients
Also used off-label for Pneumocystis pneumonia prevention
Cons
Risk of hyperkalemia, even without typical risk factors
Risk of blood cell disorders, including anemia and low platelets
Risk of severe skin reactions, including Stevens-Johnson syndrome
Can interfere with certain lab tests, including creatinine measurements
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