What Are the Most Common Antibiotics for Urinary Tract Infections?

Urinary tract infections (UTIs) are bacterial infections of the urinary tract. The most common type of UTI is cystitis which occurs in the lower portion of the urinary tract when bacteria enter the urethra and travel to the bladder.

As the bacteria multiply in the urinary tract, they cause symptoms such as pain with urination, feeling like you need to urinate more frequently, feeling the need to urinate even if you’ve just emptied your bladder, and blood in the urine. 

If you are diagnosed with a UTI, your healthcare provider will prescribe antibiotics. Antibiotics commonly recommended to treat UTIs are Macrobid (nitrofurantoin), Bactrim (trimethoprim/sulfamethoxazole), and Monurol (fosfomycin).

Fluoroquinolones like ciprofloxacin are no longer routinely recommended due to their side effects and increasing bacterial resistance.

This article will discuss the most common antibiotics used to treat UTIs, how they work, their side effects, and more.

Commonly Used Antibiotics for Urinary Tract Infections

UTIs are caused by bacteria and require antibiotics to treat them. These antibiotics may include:

• Macrobid, Macrodantin (nitrofurantoin)
• Bactrim, Bactrim DS (trimethoprim/sulfamethoxazole)
• Monurol (fosfomycin)
• Fluoroquinolones, such as ofloxacin, ciprofloxacin, or levofloxacin (only if other options are not suitable)

Nitrofurantoin

Nitrofurantoin is effective against most bacteria that commonly cause UTIs. There is minimal bacterial resistance to nitrofurantoin, making it a good first-line option.

If prescribed nitrofurantoin, you will typically take it for five days. 

Trimethoprim/Sulfamethoxazole

Trimethoprim/sulfamethoxazole is a combination medication containing two antibiotics.

Although it can be an effective treatment for UTIs, in recent years, bacterial resistance has increased. Therefore, this drug is usually only used in areas where the resistance rate is less than 20%.

This antibiotic cannot be taken by people who are allergic to sulfa drugs. If prescribed it, you will typically take it for three days. 

Fosfomycin

Fosfomycin is another suitable antibiotic option for UTIs due to minimal bacterial resistance. However, it appears to be less effective than other standard short-course treatments.

The treatment course is just a single dose, making it a convenient option. It comes as a powder that needs to be mixed with a half-cup (3 to 4 ounces) of cool water before drinking. You do not need to take it with food.

Fluoroquinolones

Fluoroquinolones are a class of antibiotics that include ciprofloxacin, ofloxacin, and levofloxacin.

These medications should be used only if other options are not suitable. Increasing bacterial resistance to fluoroquinolones has made this class of antibiotics less useful for UTI treatment in recent years.

How Do Antibiotics Treat UTIs?

Antibiotics taken by mouth work to treat bacterial UTIs through the following steps:

1. The antibiotic is absorbed in the gastrointestinal tract and enters the bloodstream.
2. It travels in the bloodstream to the kidneys, where it is delivered to the urinary tract.
3. The drug is then filtered into the urine.
4. As the urine enters the bladder, it comes into contact with and kills the bacteria causing the infection.
   

Side Effects of Antibiotics

Like most antibiotics, the ones prescribed for UTIs have the potential to cause side effects.

Nausea and stomach upset are common ones that can occur with any of the three antibiotics commonly used for UTIs.

Other common side effects include the following:

Nitrofurantoin

• Loss of appetite
• Headache
• Flatulence

Trimethoprim/sulfamethoxazole

• Loss of appetite
• Skin rash or redness

Fosfomycin

• Diarrhea
• Headache
• Backache
• Vaginitis
• Stuffy nose

Most side effects are mild and temporary while taking antibiotics. If you experience side effects that are severe enough to consider stopping treatment, contact a healthcare provider to see if an alternative antibiotic needs to be substituted to complete therapy.

How Long Do Antibiotics Take to Treat a UTI?

Symptoms of a UTI improve rapidly after starting antibiotics, usually within a few hours. Do not stop taking antibiotics once you start to feel better, and do not save antibiotics to use later.

It can take several days to clear the infection fully, so it is important to finish the entire course of antibiotics prescribed (usually three to five days).

Contact your healthcare provider for reevaluation if you notice no improvement in symptoms after starting antibiotics or if symptoms worsen.

Are There Over-the-Counter Remedies for UTIs?

There are no over-the-counter (OTC) treatments to cure a UTI, though some OTC products can help temporarily relieve the symptoms.

AZO (phenazopyridine) is a bladder anesthetic that temporarily relieves symptoms of burning, pain, urgency, and frequency but does not treat the bacterial infection.

You should always see a healthcare provider if you suspect a UTI. An untreated infection can progress up the urinary tract to evolve into a more severe infection of the kidneys (pyelonephritis). 

Summary

UTIs are a common bacterial infection that requires treatment with antibiotics. The most commonly prescribed antibiotics for UTIs are nitrofurantoin, trimethoprim-sulfamethoxazole, and fosfomycin.

Your healthcare provider will select an appropriate antibiotic based on what they know about the most common bacteria in your local area.

Most antibiotic regimens for UTIs are one to five days in length. It is important to finish all of the prescribed antibiotics and return to see a healthcare provider if your symptoms do not improve after starting treatment.