UTI Treatment Regimens

1. Uncomplicated Cystitis (Adult Female)

• No urine culture required initially for uncomplicated cystitis
• If community TMP-SMX resistance is ≥20%, use an alternative agent
• Beta-lactams (amoxicillin-clavulanate, cefpodoxime, cefdinir, cefaclor) in 3-7 day courses are appropriate if first-line agents are contraindicated
• Fluoroquinolones should be reserved for other uses - not recommended for uncomplicated cystitis

2. Complicated UTI / Pyelonephritis (Outpatient)

• Urine culture is advised
• Treat ≥7 days for mild symptoms; 14 days for severe symptoms or clear pyelonephritis
• Consider an IV dose of ceftriaxone if sensitivity is uncertain
• Admit if the patient is significantly ill, unable to retain fluids/medications, or pregnant
• Consider IV-to-oral step-down once clinical improvement is achieved

3. Inpatient Pyelonephritis / Complicated UTI (IV Regimens)

4. Special Populations

Pregnancy

• First line: Amoxicillin 500 mg PO BID-TID x 3-7 days, or Cephalexin 500 mg PO BID-QID x 3-7 days
• Nitrofurantoin: still class B but avoid in 1st trimester unless no other option (concerns re: birth defects)
• Avoid: fluoroquinolones and tetracyclines throughout pregnancy
• Beta-lactams, vancomycin, nitrofurantoin (2nd/3rd trimester), metronidazole, clindamycin, and fosfomycin are generally safe

HIV/AIDS

• Fluoroquinolones are the drug of choice (TMP-SMX resistance increased due to Pneumocystis prophylaxis)
• Use culture/sensitivity to guide therapy when available
• Close follow-up at 1 week; consider infectious disease consultation

Urethritis (vs. cystitis)

• Ceftriaxone 250 mg IM + Azithromycin 1 g single dose OR + Doxycycline 100 mg BID x 7 days
• Culture for Chlamydia and N. gonorrhoeae
• Fluoroquinolones no longer recommended (gonococcal resistance)

5. Pediatric UTI (Harriet Lane Handbook)

• Parenteral antibiotics for children who are toxic, dehydrated, or unable to tolerate oral medication
• If inadequate response: rule out renal abscess or obstruction; obtain renal bladder ultrasound (RBUS)
• VUR prophylaxis: TMP-SMX reduces recurrence risk by ~50% (no significant difference in renal scarring)
• Asymptomatic bacteriuria in afebrile children with normal urinary tract: antibiotics NOT necessary

6. Recurrent UTI (>2 in 6 months or >3 in 12 months)

• Culture and treat empirically; refer to primary care for follow-up culture and possible prophylaxis
• Prophylaxis options: continuous, postcoital, or intermittent self-treatment
• Relapse (same organism): treat with an alternative agent from the complicated UTI list
• Adjuncts: increased fluids, frequent voiding, phenazopyridine 200 mg TID for dysuria relief, cranberry juice (mildly effective for recurrence prevention)

Nitrofurantoin, TMP-SMX DS, and Fosfomycin: Monotherapy, Not Combination

Why They Are Used Alone (Not Together)

• Add no clinical benefit (each covers uncomplicated cystitis adequately on its own)
• Increase side effect burden unnecessarily
• Increase cost
• Contribute to antimicrobial resistance (unnecessary antibiotic pressure)

How to Choose Between Them

1. Nitrofurantoin is preferred when TMP-SMX resistance is high locally (≥20%), as it retains activity against nearly all uropathogenic E. coli. It is considered the safest in terms of ecological impact. Avoid if early pyelonephritis is suspected (poor tissue penetration beyond the bladder) or in renal insufficiency (GFR <45 mL/min - drug doesn't reach adequate urinary levels and may accumulate).
2. TMP-SMX DS is chosen when local resistance is known to be <20%. It is inexpensive, widely available, and has a 3-day course (good compliance). Avoid if the patient has sulfa allergy or has recently used it (higher chance of resistant organism).
3. Fosfomycin is chosen for convenience (single dose = best compliance), when both other agents are unsuitable, or when ESBL-producing organisms are a concern. It is often more expensive and may be slightly less effective.

Bottom Line (IDSA Guideline Principle)

Fluoroquinolones (ciprofloxacin, levofloxacin) are deliberately excluded from first-line uncomplicated cystitis precisely to preserve them for more serious infections - they work, but the collateral damage to resistance patterns is too high a price for a benign self-limited condition.

Clinical Presentation of Uncomplicated Cystitis in Adult Female

Symptoms (Classic Triad + More)

Differential Diagnosis for Dysuria in Sexually Active Young Female

Hematuria (micro or gross) is common in cystitis but absent in urethritis and vaginitis - a useful distinguishing feature. - Comprehensive Clinical Nephrology, 7th Ed.

Diagnosis

• Urine culture not routinely needed for uncomplicated cystitis - history alone is highly reliable
• Urinalysis: pyuria (almost universal), hematuria, bacteriuria, positive leukocyte esterase and nitrites on dipstick
• Threshold for bacteriuria: ≥10⁵ colony-forming units/mL (traditional), but some women with cystitis have lower counts

Risk Factors

• Female sex (short urethra, proximity of urethra to anus)
• Sexual activity
• Use of spermicides
• Prior UTI

Role of Urine Alkalisation in UTI

Rationale / Proposed Mechanism

1. Directly reduce mucosal irritation - less chemical burning on inflamed mucosa
2. Reduce symptom severity by local action on bladder/urethra
3. Modulate antibiotic activity - at alkaline pH, some antibiotics (e.g., aminoglycosides, macrolides) have lower minimum inhibitory concentrations (MICs), potentially enhancing bactericidal effect
4. Prevent crystalluria - relevant with certain drugs

Important: Urine alkalisation is purely symptomatic adjunct therapy, not an antibiotic. It does not eradicate the infection. - PMC review, O'Kane 2016

What the Evidence Actually Says

Alkasol Syrup

Composition

• Active ingredient: Disodium hydrogen citrate (a citrate salt)
• Some formulations also contain citric acid

Mechanism of Alkalisation

Indications

Dosing (Alkasol Syrup - Typical)

• Adult: 5-10 mL (1-2 teaspoons) in water, 3 times daily after meals
• Continue until symptoms resolve (usually 2-3 days alongside antibiotics)
• Always dilute - do not take neat

Important Points

Summary: How They Fit Together in Practice

Uncomplicated Cystitis in Adult Female
│
├── ANTIBIOTIC (curative - kills bacteria)
│     Nitrofurantoin 100 mg BID x 5 days  ← first choice
│     OR TMP-SMX DS BID x 3 days
│     OR Fosfomycin 3g single dose
│
├── SYMPTOM RELIEF (adjunct - reduces burning/dysuria)
│     Alkasol syrup (disodium hydrogen citrate) - alkalises urine
│     OR Phenazopyridine 200 mg TID (bladder analgesic, turns urine orange)
│
└── SUPPORTIVE
      Increased fluid intake + frequent voiding