Post-Coital Antibiotic Prophylaxis for Recurrent UTIs
For premenopausal women with recurrent UTIs clearly linked to sexual activity, take a single low-dose antibiotic within 2 hours after intercourse for 6-12 months. 1, 2
Confirming the Diagnosis
Before initiating any prophylaxis, confirm you are dealing with true recurrent UTIs defined as ≥2 culture-positive UTIs in 6 months or ≥3 in one year. 2, 3 Verify eradication of the previous UTI with a negative urine culture 1-2 weeks after treatment before starting prophylaxis. 2
First-Line Behavioral Modifications
Start with these evidence-based lifestyle changes before or alongside antibiotic prophylaxis: 1, 2
- Void immediately after sexual intercourse 2, 4
- Maintain adequate hydration (2-3 liters daily) to promote frequent urination 2, 3
- Avoid prolonged holding of urine 2
- Avoid sequential anal and vaginal intercourse 2
- Discontinue spermicide use if applicable, as this disrupts normal vaginal flora 1, 4
- Avoid harsh vaginal cleansers 2
Sexual intercourse is the strongest predictor of recurrent UTIs in young women, making post-coital prophylaxis particularly effective for this population. 5
Post-Coital Antibiotic Prophylaxis Regimen
Preferred Antibiotics (in order of preference):
- Nitrofurantoin 50 mg - single dose within 2 hours after intercourse 1, 2
- Trimethoprim-sulfamethoxazole 40/200 mg - single dose within 2 hours after intercourse 1, 2
- Trimethoprim 100 mg - single dose within 2 hours after intercourse 1, 2
Avoid fluoroquinolones and cephalosporins as first-line agents due to concerns about antimicrobial resistance and antibiotic stewardship. 1
Duration and Monitoring:
- Continue prophylaxis for 6-12 months 1, 2
- Base antibiotic choice on prior urine culture results and susceptibility patterns from the patient's previous infections 1, 2
- Consider rotating antibiotics every 3 months if breakthrough infections occur, to reduce development of resistance 1
- Obtain urine culture with each symptomatic episode before treating 2
Post-coital prophylaxis reduces recurrent cystitis by approximately 90% when used correctly. 6
Non-Antibiotic Alternatives
If the patient prefers to avoid antibiotics or has contraindications: 1, 2
- Methenamine hippurate 1, 2
- Lactobacillus-containing probiotics (specifically L. rhamnosus GR-1 or L. reuteri RC-14) 1, 2
These can be used alone or in combination, though the evidence supporting them is weaker than for antibiotic prophylaxis. 1
Critical Pitfalls to Avoid
- Never treat asymptomatic bacteriuria - this increases antimicrobial resistance and paradoxically increases symptomatic infection risk 3, 7
- Do not prescribe prolonged antibiotic courses (>5 days) for acute treatment, as this fosters resistance 1
- Do not repeat urine cultures after successful treatment if symptoms have resolved 2
- Avoid unnecessary broad-spectrum antibiotics - stick to narrow-spectrum agents when possible 1
When Post-Coital Prophylaxis Fails
If breakthrough infections continue despite post-coital prophylaxis: 2, 3
- Switch to continuous daily antibiotic prophylaxis with the same preferred agents (nitrofurantoin, trimethoprim-sulfamethoxazole, or trimethoprim) 3
- Reassess for complicating factors including anatomical abnormalities, neurogenic bladder, immunosuppression, or nephrolithiasis 1
- Consider imaging studies only if specific risk factors suggest structural abnormalities 2
Special Population: Postmenopausal Women
If the patient is postmenopausal, vaginal estrogen therapy with or without lactobacillus probiotics should be the first-line approach instead of post-coital antibiotics. 1, 3 This addresses the underlying atrophic vaginitis that predisposes to recurrent UTIs in this population.