What antibiotics are commonly used to treat urinary tract infections (UTIs)?

A handful of antibiotics are used to treat the most common urinary tract infections (UTIs). In 75-95% of these cases, the infection is caused by bacteria called Escherichia coli (E. coli), so experts know which antibiotics work well against the infection. These antibiotics are called first-line antibiotics.

They are given orally and include:

• Nitrofurantoin (Macrobid)
• Fosfomycin (Monurol)
• Sulfamethoxazole-trimethoprim (Septra or Bactrim)

Amoxicillin and ampicillin are no longer used because of a high level of antibiotic resistance.

Antibiotics for acute and uncomplicated urinary tract infections

First-line treatment for an uncomplicated UTI may start with a single dose of fosfomycin or nitrofurantoin twice per day for five days, or sulfamethoxazole-trimethoprim twice per day for three days. These medications can be started based on your symptoms and urinalysis results, and should be effective in most cases.

Although much less common, men may also get this type of UTI. The choice of antibiotics is the same, but they may be given for a longer time because bacteria may move into the prostate gland and take longer to treat.

When doctors diagnose an uncomplicated UTI, they are usually diagnosing a type of UTI called cystitis, which means a bladder infection. In fact, the terms UTI, cystitis and bladder infection are often used interchangeably. “Acute uncomplicated cystitis” is another medical term for a common UTI that has not spread or become severe.

The term uncomplicated refers to a simple UTI found in a generally healthy adult who:

• Is not pregnant or postmenopausal
• Is not immunocompromised
• Has no structural abnormalities in the urinary tract
• Has no other diseases

Antibiotics for more complicated urinary tract infections

A different antibiotic may be better for a more severe or stubborn UTI. This may include a UTI that:

• Spreads to the kidneys
• Has unusual symptoms
• Comes back
• Is not responding to treatment

Additionally, there is a medical category of “complicated” UTIs that may require a different antibiotic regimen.

Complicated UTIs include UTIs that occur:

• In a person with a childhood history of UTIs
• In a person with a weakened immune system
• In a child or postmenopausal woman
• During pregnancy
• With a medical condition, like diabetes
• With an abnormality of the urinary tract, like a stone, obstruction, catheter or kidney deformity

In these cases, a urine culture may be done to make the choice of antibiotic. A urine culture grows the bacteria from the urine so that it may be identified under a microscope and tested for antibiotic sensitivity. The best antibiotic will be determined by the culture and sensitivity results.

No matter what antibiotic your health care provider prescribes, it is important to take the entire course as directed. Stopping early can lead to antibiotic resistance.

If your antibiotic doesn’t seem to be working and symptoms don’t go away or come right back, let your health care provider know.

Other antibiotics and treatments for urinary tract infections

Other antibiotics may be as effective as first-line antibiotics but have more side effects or risks of complications. They are not commonly used. They include:

• Fluoroquinolones
• Ofloxacin
• Ciprofloxacin
• Levofloxacin

Antibiotics called beta-lactams may be used when other first-line antibiotics are unavailable or cannot be used for any other reason. They include:

• Amoxicillin-clavulanate
• Cefdinir
• Cefaclor

These are not usually first-line choices because they are broad-spectrum antibiotics that have a higher risk of causing antibiotic resistance.

Another drug that is frequently prescribed for a UTI is phenazopyridine, available under several brand names such as Pyridium. This medication is not an antibiotic and does not cure a UTI. It is used to relieve symptoms of pain, burning, urgency and pressure.