Macrobid (Nitrofurantoin) is NOT Appropriate for This Patient
Nitrofurantoin should not be used in men with enlarged prostates and possible UTI because it does not penetrate prostatic tissue and cannot treat prostatitis, which is frequently present in men with UTI symptoms and BPH. 1
Why Nitrofurantoin Fails in This Clinical Scenario
Poor Prostatic Penetration
- Nitrofurantoin achieves therapeutic concentrations only in the bladder and urine, not in prostatic tissue 2
- In men with enlarged prostates, UTI symptoms often indicate prostatic involvement (acute bacterial prostatitis), which requires antibiotics that penetrate the prostate 2
- The frequency of prostate involvement in men presenting with UTI symptoms is unknown, but clinical experience suggests it is common enough to avoid nitrofurantoin as first-line therapy 2
High Treatment Failure Rates in Men
- Retrospective studies show approximately one-third of men treated with nitrofurantoin for UTI required a second course of antibiotics within 60-90 days 2
- While not all retreatment represents nitrofurantoin failure, the high rate is concerning and suggests inadequate treatment of prostatic infection 2
Risk of Progression to Serious Infection
- Urinary tract infections with systemic symptoms (fever, chills, flank pain) cannot be treated with nitrofurantoin 2
- Men with BPH and UTI are at higher risk for bacteremia—one study found bacterial growth in 9% of blood cultures from elderly men with BPH and UTI 3
What You Should Prescribe Instead
First-Line Antibiotic Choice
- Fluoroquinolones (ciprofloxacin or levofloxacin) are the preferred empiric treatment for men with suspected UTI and enlarged prostate 2
- These agents achieve excellent prostatic tissue penetration and cover the most common uropathogens in this population 3
- Treatment duration should be 7-14 days (not the 3-5 days used for simple cystitis in women) to adequately treat potential prostatic involvement 2
Alternative if Fluoroquinolone-Resistant or Contraindicated
- Trimethoprim-sulfamethoxazole can be used if local resistance patterns are favorable (though resistance rates exceed 50% in many areas for E. coli from elderly men with BPH) 3
- Third-generation cephalosporins may be considered, though resistance rates are also concerning 3
Critical Diagnostic Steps Before Treatment
Confirm the Diagnosis
- Obtain urinalysis and urine culture before starting antibiotics 1, 4
- Perform digital rectal examination to assess for prostatic tenderness (suggests acute prostatitis requiring longer treatment) 4
- Check for systemic symptoms (fever, chills, rigors) that would indicate tissue invasion requiring parenteral therapy 1, 2
Rule Out Asymptomatic Bacteriuria
- Older men frequently have asymptomatic bacteriuria (ABU), which should NOT be treated 1
- Only treat if patient has acute onset of dysuria, frequency, urgency, or systemic symptoms 1
- Atypical presentations in elderly include new confusion, functional decline, or falls 1
When Nitrofurantoin Might Be Acceptable (Rarely)
Nitrofurantoin could be considered ONLY if:
- Urine culture confirms infection with nitrofurantoin-susceptible organism 1, 3
- Patient has NO systemic symptoms 2
- Digital rectal exam shows NO prostatic tenderness 2
- Patient has failed or cannot tolerate fluoroquinolones 2
- Close follow-up (48-72 hours) is ensured to detect treatment failure 2
Even in these circumstances, fluoroquinolones remain superior due to prostatic penetration. 2
Additional Management Considerations
Address the Underlying BPH
- The enlarged prostate is a risk factor for recurrent UTI and should be treated 1, 4
- Consider alpha-blocker (tamsulosin, alfuzosin) to improve bladder emptying 1, 4
- If prostate >30cc, add 5-alpha reductase inhibitor (finasteride, dutasteride) to reduce prostate size and prevent complications 1, 4, 5