Antibiotics for Urinary Tract Infections & Bladder Infection

Based on International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women 1.

Do you need antibiotics for UTI?

The most common cause of UTI is bacterial infection. Fungal and parasitic infections very rarely cause UTIs.

Typical symptoms of a bladder infection (cystitis) include urinary frequency and dysuria (painful or difficult urination) without fever. If both symptoms (frequency and dysuria) are present, the likelihood of cystitis is > 90% and antibiotic treatment is indicated2.

Adequate fluid intake is very important during treatment.

Best Antibiotics for UTIs

The best antibiotic for bladder infection (acute cystitis) should provide an optimal balance between effectiveness, safety, and cost. Best antibiotic is NOT always the strongest.

First-line treatment options which are recommended by Infectious Diseases Society of America (IDSA) guidelines represent the best treatments:

  • Nitrofurantoin monohydrate/macrocrystals is #1 treatment choice according to the latest IDSA 2010 Guidelines.
  • Fosfomycin is effective, very convenient, and has excellent tolerability and safety.
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choice of UTI, bladder infection antibiotic infographic

No single medication is considered the best antibiotic. Choosing an antibiotic depends on medication availability, specific patient history (e.g. allergic reactions), local resistance rates.

First line medications

Nitrofurantoin (Macrobid®, Macrodantin®)

Nitrofurantoin microcrystalline (micro) versus Nitrofurantoin macrocrystalline (macro)

Nitrofurantoin was initially manufactured in microcrystalline form (nitrofurantoin monohydrate).

Both micro and macro formulations of nitrofurantoin have comparable antibacterial efficacy.

Macrodantin® contains nitrofurantoin macrocrystals.

Macrobid® contains two forms of nitrofurantoin: 25% of macrocrystals and 75% of microcrystals.

Benefits:

  • Current evidence supports the use of nitrofurantoin as first-line therapy.
  • Most E. coli are sensitive to nitrofurantoin.
  • Bacteriocidal in urine.
  • Unlike many other broad spectrum antibiotics nitrofurantoin does not produce systemic antibacterial action. As a result nitrofurantoin does not suppress normal vaginal and gastrointestinal microflora and has minimal propensity for resistance.
  • Limited effects on resistance development to other antimicrobial agents.

Disadvantages

  • Nitrofurantoin is not effective for upper urinary tract infections (pyelonephritis). It has poor penetration into the renal tissue.
  • Unsafe in patients with creatinine clearance less than 60 mL/min.
  • Longer treatment course than with other medications.

Macrobid® dosage: 100 mg twice per day for 5-7 days.

Macrodantin® dosage: 50-100 mg 4 times a day for 7 days.

Fosfomycin (Monurol®)

Fosfomycin tromethamine is a synthetic, broad spectrum, bactericidal antibiotic.

Benefits

  • Highly effective - fosfomycin has cure rate >80%3.
  • Moreover, fosfomycin is highly effective in the treatment of multidrug-resistant urinary tract infections 4.
  • Very convenient single dose regimen.
  • Rapid absorption after oral intake and very high and sustained concentrations in urine.
  • Fosfomycin is well tolerated and generally free of serious side effects.
  • May be used in patients with multiple antibiotic allergies due to its unique chemical structure.
  • There is minimal risk of cross-resistance between fosfomycin and other antibacterial agents. Fosfomycin has a unique chemical structure that is distinct from all other antibiotic classes.

Disadvantages

  • Fosfomycin may be less effective. Fosfomycin has lower cure rate than TMP-SMX and nitrofurantoin in the treatment of bladder infection.
  • This antimicrobial agent is not widely available in the United States.
  • Does not work for pyelonephritis.
  • Expensive.
  • Poor insurance coverage.

Fosfomycin (Monurol) dosage: 3 g single dose.

Trimethoprim/sulfamethoxazole (Bactrim®, Bactrim® DS, Septra®)

Trimethoprim/sulfamethoxazole (TMP-SMX) is recommended to use only in regions where the prevalence of TMP-SMX-resistant uropathogens does not exceed 20%.

Benefits

  • TMP-SMX has good activity against common urinary tract pathogens.
  • TMP-SMX penetrates into both lower and upper urinary tract.
  • Convenient twice daily schedule.
  • Low cost.

Disadvantages

  • Increasing resistance of E. coli.
  • TMP-SMX should not be used empirically when local resistance is > 20%.

Trimethoprim/sulfamethoxazole dosage: 160/800 mg twice per day for 3 days.

Second line medications

Alternative antibiotics such as fluoroquinolones or beta-lactams are recommended to use when first line treatments cannot be used due to availability, allergy, or tolerance.

Important note: Not all fluoroquinolones are indicated for infections of the urinary tract. Sparfloxacin and moxifloxacin don't achieve reliable concentrations in the urine and are not approved for UTIs. Moxifloxacin and gatifloxacin are not approved as well.

Ciprofloxacin (Cipro®)

Benefits

  • Second line choice.
  • Ciprofloxacin is very effective for cystitis and pyelonephritis.
  • Excellent activity against common urinary pathogenic bacteria.
  • Ciprofloxacin achieves high concentrations in the urine.
  • Rapidly bactericidal.

Disadvantages

  • Increasing resistance of E. coli to fluoroqiunolones due to over-use.
  • Currently ciprofloxacin is not recommended as initial treatment for bladder infection in order to limit development of resistance.
  • Ciprofloxacin has wider range of severe side effects, including tendon injury, QT-prolongation.
  • Potential for drug-drug interactions.
  • Contraindicated in women who are pregnant or breastfeeding.

Ciprofloxacin (Cipro) dosage: 250 mg twice per day for 3 days.

Cipro XR dosage: 500 mg per day for 3 days.

Levofloxacin (Levaquin®)

Benefits

  • Second line choice.
  • Levofloxacin has excellent activity against variety of organisms responsible for UTIs.
  • Effective for different types of UTI, including cystitis, pyelonephritis, and complicated UTI.
  • Most recent prescribing guidelines recommend reserving levofloxacin for serious infections, such as complicated urinary tract infections and pyelonephritis.

Disadvantages

  • Increasing antimicrobial resistance to fluoroqiunolones due to over-use.
  • Contraindicated in women who are pregnant or breastfeeding.
  • More expensive than first line treatments.

Levofloxacin (Levaquin) dosage: 250 mg per day for 3 days.

Ofloxacin

Benefits

  • Effecive second line treatment choice.

Disadvantages

  • Contraindicated in women who are pregnant or breastfeeding.

Ofloxacin dosage: 200 mg per day for 3 days or 400 mg single dose.

Third line medications

Amoxicillin/clavulanate (Augmentin®)

Benefits

  • Amoxicillin/clavulanate is now regarded as a third-line treatment for UTI in preference to amoxicillin alone.
  • Amoxicillin/clavulanate is an appropriate choice for bladder infection when other recommended antibiotics cannot be used.

Disadvantages

  • Amoxicillin-clavulanate is less effective than ciprofloxacin or levofloxacin.
  • Expensive.

Amoxicillin/clavulanate (Augmentin) dosage:
500/125 mg twice per day for 7 days.
875/125 mg twice per day for 7 days.

Although resistance to the third-generation cephalosporins is lower than to the first generation, these agents are considered third-line agents because of their cost and efficacy.

Cefdinir (Omnicef®)

Benefits

  • Third line choice.
  • Resistance to the 3rd generation cephalosporins is lower than to cephalexin (the member of 1st generation).
  • Cefdinir is a suitable option for persons who are intolerant to trimethoprim-sulfamethoxazole, for UTIs which do not respond to other medications.

Disadvantages

  • High cost.
  • Cure rates are not very high.

Cefdinir (Omnicef) dosage: 300 mg twice per day for 7 days.

Cefpodoxime

Benefits

  • Third line choice.
  • May be used for UTIs which do not respond to other medications.

Disadvantages

  • High cost.
  • Cure rates are not very high.

Cefpodoxime dosage: 100 mg twice per day for 7 days.

Further reading


Antibiotics NOT recommended by Guidelines

Amoxicillin, Ampicillin

Amoxicillin is no longer recommended for urinary tract infections because of resistance and higher recurrence rates1.

Benefits

  • Amoxicillin is FDA approved for UTIs.
  • Currently amoxicillin is not suitable as empiric therapy for cystitis but can be prescribed if urine culture shows susceptibility.
  • Amoxicillin reaches high urinary concentrations.
  • Inexpensive.
  • Safe to use during pregnancy.

Disadvantages

  • Most E. coli are now is resistant to amoxicillin, so it is not good for empirical treatment.
  • Amoxicillin or ampicillin have relatively poor efficacy.
  • Patients are more likely to fail with amoxicillin therapy than with first line medications.

Amoxicillin dosage: 250 mg 4 times daily for 7 days.

Cephalexin (Keflex®)

Recently cephalexin has fallen out of favour as a recommended treatment option for UTI due to increasing resistance of E. coli1.

Benefits

  • Cephalexin (Keflex) is FDA approved for UTIs.
  • Cephalexin reaches high urinary concentrations.
  • May be appropriate treatment in certain cases (e.g. UTI in children5, cystitis during pregnancy).
  • Generally well tolerated.
  • Cheap.

Disadvantages

  • High resistance rates among E. coli to cephalexin.
Cephalexin dosage: 250 mg 4 times daily for 7 days.

Azithromycin (Zithromax®, Z-Pack®)

Urinary concentrations of azithromycin are low. This drug is not licensed for UTIs. Azithromycin may be used to treat only certain STD-caused infections of the urinary tract.

Other macrolide antibiotics also lack an indication for UTI therapy and are not useful as well.

Clindamycin

Clindamycin is not licensed for UTIs. Clindamycin does not achieve sufficient concentrations in the urinary tract. Does not act against the common causes of urinary tract infection.

Doxycycline, Minocycline, Tetracycline

Current IDSA Guidelines1 don't recommend tetracycline antibiotics (doxycycline, minocycline, tetracycline) for UTI because of resistance problems.

Doxycycline is effective for UTI caused by P. aeruginosa, Klebsiella pneumoniae.

UTI Diagnosis

Urine cultures are recommended only for persons with:

  • suspected acute pyelonephritis
  • symptoms that do not resolve within 2-4 weeks after the completion of treatment
  • atypical symptoms.

Further reading

References

  • 1. Gupta K, Hooton TM, Naber KG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: a 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis. 2011;52(5):e103–e120.
  • 2. Scottish Intercollegiate Guidelines Network Management of suspected bacterial urinary tract infection in adults. 2006. NHS Quality Improvement Scotland
  • 3. Stein GE. Comparison of single-dose fosfomycin and a 7-day course of nitrofurantoin in female patients with uncomplicated urinary tract infection. Clin Ther. 1999 Nov;21(11):1864-72.
  • 4. Giancola SE, Mahoney MV, Hogan MD, Raux BR, McCoy C, Hirsch EB. Assessment of Fosfomycin for Complicated or Multidrug-Resistant Urinary Tract Infections: Patient Characteristics and Outcomes. Chemotherapy. 2017;62(2):100-104.
  • 5. Butler CC, O'Brien K, Wootton M, DUTY Study Team. Empiric antibiotic treatment for urinary tract infection in preschool children: susceptibilities of urine sample isolates. Fam Pract. 2016 Apr;33(2):127-32.

Published: May 21, 2018 by eMedExpert staff
Last updated: May 21, 2018

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