What are the recommended antibiotics for treating uncomplicated Urinary Tract Infections (UTIs) and mastitis?

Recommended Antibiotics for UTIs and Mastitis

Urinary Tract Infections (UTIs)

For uncomplicated UTIs in adults, nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days is the recommended first-line treatment due to its high efficacy (93% clinical efficacy) and minimal resistance patterns. 1

First-line options for uncomplicated UTIs:

1. Nitrofurantoin monohydrate/macrocrystals

   • Dosage: 100 mg twice daily for 5 days
   • Efficacy: 93% clinical efficacy, 88% microbiological efficacy 1
   • Advantages: Low resistance rates (approximately 2%) 2
   • Contraindications: Not for use in patients with significant renal impairment (creatinine clearance <30 mL/min), pregnant women in third trimester, or patients with G6PD deficiency 1

2. Trimethoprim-sulfamethoxazole (TMP-SMX)

   • Dosage: 160/800 mg (one double-strength tablet) twice daily for 3 days 1
   • Efficacy: 93% clinical efficacy, 94% microbiological efficacy 1
   • Caution: Consider local resistance patterns (resistance approaches 18-22% in some US regions) 1
   • FDA-approved dosage: One double-strength tablet every 12 hours for 10-14 days (though shorter courses are now recommended in guidelines) 3

3. Fosfomycin trometamol

   • Dosage: 3 g single dose
   • Efficacy: 91% clinical efficacy, 80% microbiological efficacy 1

Second-line options:

1. Fluoroquinolones (ofloxacin, ciprofloxacin, levofloxacin)

   • Should be reserved for more serious infections due to:
     • Collateral damage to normal flora
     • FDA warnings about serious side effects
     • Need to preserve effectiveness for more serious infections 1
   • Efficacy: 90% clinical efficacy, 91% microbiological efficacy 1

2. β-Lactams (amoxicillin-clavulanate, cefdinir, cefaclor, cefpodoxime-proxetil)

   • Not recommended as first-line due to inferior efficacy and more adverse effects
   • Efficacy: 89% clinical efficacy, 82% microbiological efficacy 1

Special populations:

1. Patients with renal impairment:

   • For severe renal impairment (GFR <30 mL/min): TMP-SMX with dose adjustment to 160/800 mg every 24 hours 1
   • Nitrofurantoin should be avoided when creatinine clearance <30 mL/min 1
   • For GFR <15 mL/min: TMP-SMX is not recommended 3

2. Men with UTI:

   • Longer treatment duration (7 days) with TMP-SMX, trimethoprim, or nitrofurantoin 4
   • Always obtain urine culture and consider possibility of urethritis and prostatitis 4

3. Elderly patients (non-frail, no relevant comorbidities):

   • Same first-line antibiotics as younger adults
   • Obtain urine culture to adjust antibiotic choice after initial empiric treatment 4

Mastitis

Note: The provided evidence does not contain specific information about mastitis treatment. Based on general medical knowledge:

For lactational mastitis:

• First-line: Dicloxacillin or cephalexin 500 mg four times daily for 7-10 days
• For penicillin allergy: Clindamycin 300-450 mg four times daily for 7-10 days

For non-lactational mastitis:

• Treatment depends on the underlying cause, often requiring broader spectrum antibiotics

Clinical Pearls and Pitfalls

For UTIs:

• Diagnosis can be made with high probability based on focused history of lower urinary tract symptoms (dysuria, frequency, urgency) and absence of vaginal discharge 1
• No routine post-treatment urinalysis or cultures are needed if symptoms resolve 1
• If symptoms don't improve within 72 hours, obtain urine culture and consider alternative antibiotics 1
• Check baseline potassium before starting TMP-SMX as it can cause hyperkalemia 1
• Avoid treating asymptomatic bacteriuria in non-pregnant women as it promotes antimicrobial resistance without clinical benefit 1

For both conditions:

• Consider local resistance patterns when selecting empiric therapy
• Ensure adequate hydration during treatment
• Complete the full course of antibiotics even if symptoms improve quickly