Urinary Tract Infection - Medications

Medications

Although antibiotics are the first treatment choice for urinary tract infections, antibiotic-resistant strains of E. coli, the most common cause of UTIs, are increasing worldwide. As more bacteria have become resistant to the standard UTI treatment trimethoprim-sulfamethoxazole (TMP-SMX), more doctors have prescribed quinolone antibiotics to treat UTIs. In some areas, quinolones have now overtaken TMP-SMX as the most commonly prescribed antibiotic for UTIs. Researchers are concerned that resistance may develop to these drugs as well.

The following are some of the antibiotic classes used most commonly to treat UTIs:

---

---

Beta-Lactams

The beta-lactam antibiotics share common chemical features and include penicillins, cephalosporins, and some newer similar drugs.

Penicillins (Amoxicillin). Until recent years, the standard treatment for a UTI was 10 days of amoxicillin, a penicillin antibiotic, but it is now ineffective against E. coli bacteria in up to 25% of cases. A combination of amoxicillin-clavulanate (Augmentin) is sometimes given for drug-resistant infections. Amoxicillin or Augmentin may be useful for UTIs caused by Gram-positive organisms, including Enterococcus species and S. saprophyticus.

Cephalosporins. Antibiotics known as cephalosporins are alternatives for infections that do not respond to standard treatments or for special populations. They are often classed as first, second, or third generation. Cephalosporins used for treatment of UTIs include cephalexin (Keflex), cefadroxil (Duricef) cefuroxime (Ceftin),loracarbef (Lorabid), and cefixime (Suprax, among others.

Other Beta-Lactam Drugs. Other beta-lactam antibiotics have been developed. For example, pivmecillinam (a form of mecillinam), is commonly used in Europe for UTIs.

Trimethoprim-Sulfamethoxazole (TMP-SMX)

The typical treatment for an uncomplicated UTI is a 3-day course of the combination drug trimethoprim-sulfamethoxazole, commonly called TMP-SMX (such as Bactrim, Cotrim, or Septra). A 1-day course is somewhat less effective but poses a lower risk for side effects. Longer courses (7 - 10 days) work no better than the 3-day course and have a higher rate of side effects.

TMP-SMX should not be used in patients who are allergic to sulfa drugs. Allergic reactions can be very serious. Trimethoprim (such as Proloprim or Trimpex) is sometimes used alone in those allergic to sulfa drugs. TMP-SMX can interfere with the effectiveness of oral contraceptives. High rates of bacterial resistance to TMP-SMX exist in many parts of the United States.