A urinary tract infection or UTI occurs when germs invade the bladder or kidneys. Bacteria are the most common invaders, with Escherichia coli topping the list. E. coli and other digestive-tract organisms may find their way into the urinary tract and cause an infection. Fortunately, numerous options for antibiotic therapy exist. Ideally, an antibiotic is chosen based on culture and sensitivity testing, but often this information is not available and choices are made based on the most likely causative organism.
Trimethoprim/Sulfamethoxazole
TMP/SMX, bactrim and septra are all names for this drug, which is commonly used to treat a UTI. It is a sulfa derivative and should not be taken by those with a sulfa allergy. A typical regimen would be one pill twice a day for three days. Longer courses are sometimes prescribed, but increase the risk of side effects. The University of Maryland Medical Center notes that resistance to this drug is seen in many parts of the United States.
Fluoroquinolones
This group of drugs, more simply known as quinolones, has good choices for treating a UTI, especially if resistant bacteria are suspected. Ciprofloxacin, ofloxacin and levofloxacin are members of this class. Again, a three day course is common for uncomplicated UTIs. These drugs are not usually the first choice for children, as there are concerns about side effects. Additionally, they should not be taken by pregnant women. Some antibiotics in this class are available intravenously for more severe infections requiring hospitalization.
Nitrofurantoin
This antibiotic is prescribed almost exclusively for treatment or prevention of urinary tract infections. It usually requires a longer course of treatment, and is sometimes taken on a daily basis for six months or more to prevent recurrent infections. Use is not advised in pregnant women near term or nursing mothers.
Beta Lactams
Penicillins and cephalosporins fall under this category. Amoxicillin or amoxicillin combined with clavulanate to improve its bacteria killing spectrum are used in certain cases of UTI, often based on susceptibility testing. The cephalosporins such as cephalexin, cefuroxime, cefixime and cefprozil are other alternatives available in the war on bacteria in the urinary tract. Many people are allergic to penicillins and therefore should not take them. Sometimes those with a penicillin allergy may have a reaction to the cephalosporins as well.
Tetracyclines
This class includes its namesake, as well as doxycycline. These antibiotics are generally reserved for specific infections with mycoplasma or chlamydia, notes the University of Maryland Medical Center. They are not to be used in children or during pregnancy. Caution should be taken, as they can increase sensitivity to the sun.
Aminoglycosides
Gentamicin is an antibiotic in this class that is used to treat severe or resistant urinary tract infections. It is only available intravenously and is used in combination with other drugs. Possible severe side effects include damage to the inner ear or kidneys.
