TMP-SMX is the most frequently prescribed antibiotic for bladder infections. It is effective in 85 to 95 percent of cases.

In some parts of the country, TMP-SMX is becoming less effective as the bacteria that causes bladder infections have developed resistance (are no longer vulnerable) to this medication.

Currently, TMP-SMX is being recommended in areas of the country where fewer than 20% of bladder infections are resistant to it. Your physician will know which antibiotics tend to work for bladder infections in your part of the country.

Since TMP-SMX is the most cost-effective treatment for bladder infection, it is still the drug of choice in regions where significant bacterial resistance has not yet developed.

It is important to drink lots of fluids when taking medications, like TMP-SMX, that contain sulfa, to avoid developing sulpha crystals and stones in the bladder.

Trimethoprim and TMP-SMX (trimethoprim/sulfamethoxazole) have been shown to be similar in effectiveness. They are similar drugs except that TMP-SMX contains an additional antibiotic (a sulfa antibiotic), and, therefore, trimethoprim causes fewer side effects.

Despite this, trimethoprim has not been prescribed as commonly as TMP-SMX since theoretically, the combination of the two drugs should be more effective.

In the past, bladder infections were treated with 7 to 10 days of antibiotic drugs. A number of studies have shown that three days of antibiotic drugs are as effective for most people and cause fewer side effects and are lower cost.

Most experts now recommend three days of antibiotic drugs for young, healthy women, unless they have had hard-to-treat bladder infections in the past.

Men and older women are treated with 7 days of antibiotic drugs.

An older antibiotic, rediscovered and recently added, by the American College of Obstetrics and Gynecology (ACOG), to the guidelines of drugs recommended as first choice treatments for uncomplicated bladder infections.

Quinolones are highly effective for treating bladder infections. They cure approximately 95 percent of bladder infections and are used often for patients who cannot take TMP-SMX, and in regions of the country where bacteria are resistant (not vulnerable) to TMP-SMX.

They are not recommended as a first choice treatment for bladder infections because they are very expensive and because physicians like to keep them in reserve for hard-to-treat cases. If they are used too frequently, bacteria will develop resistance to them ("learn" how to survive in their presence) and they would no longer be an option for difficult cases.

Macrodantin has been used for many years for daily, long-term treatment to prevent bladder infections for patients who get them frequently. Limited studies show that this drug is probably similar in effectiveness to TMP-SMX.

Macrodantin may represent an alternative to TMP-SMX in communities where bacteria have become resistant (not vulnerable) to TMP-SMX. Unlike other antibiotic drugs used to treat bladder infections, bacteria rarely become resistant to macrodantin.

Macrodantin is more expensive than TMP-SMX.

One single dose of antibiotic is sometimes used to treat bladder infections, but it generally results in a lower cure rate and bladder infections frequently recur. As a result, most experts prefer three days of antibiotic treatment which tends to be much more effective than a single dose.

Amoxicillin and Cephalosporins tend to be especially ineffective when used as a single dose treatment.

In the past, 7 to 10 days of antibiotic drugs were the typical treatment for all patients with bladder infections. Studies have shown that 3 days of antibiotic drugs are as effective as the longer course in young healthy women with bladder infections.

Women who are pregnant, who have diabetes, or who have had symptoms of bladder infections for more than one week should be treated with 7 days of antibiotic drugs.

Men should be treated with 7 days of antibiotic drugs, and shorter courses of treatment should be avoided.

Studies show that women who use diaphragms and spermatocide cream for birth control have a higher rate of bladder infections. Using other types of birth control may be beneficial for women with frequently recurring bladder infections.

Experts recommend that women wipe from front to back after going to the bathroom so that bacteria (germs) from the gastrointestinal tract (from the rectum) are not brought close to the opening that leads to the bladder.

Cephalosporins are at least as effective as TMP-SMX (approximately 90 percent effective) but are more expensive. They also cover a wider range of bacteria and, therefore, are more likely to disturb the bacteria that live in the gastrointestinal and reproductive system, causing diarrhea and vaginal yeast infections.

Cephalosporins are a drug of choice for women who are pregnant.

Augmentin is considered a second choice treatment for bladder infections, particularly for individuals who cannot take first choice drugs such as TMP-SMX. Augmentin is effective in approximately 95 percent of people with bladder infections. It is more expensive than TMP-SMX and other available antibiotic drugs and can cause undesirable (gastrointestinal) side effects.

Augmentin is often used, however, as a first choice for bladder infections in pregnant women.

Amoxicillin and ampicillin are generally not recommended to treat bladder infections because it fails to cure the condition in approximately 50 percent of individuals.

Amoxicillin or ampicillin are sometimes used, however, when urine cultures are performed and show that the bacteria that is causing the infection is vulnerable to either of these antibiotics.

Sulfa drugs are not recommended alone to treat bladder infections. They fail to cure the infections in a large number of cases because the infection-causing bacteria have developed a resistance to this antibiotic.

Available study data fails to show that cranberry juice effectively treats or prevents urinary tract infections.

Women who are pregnant are at high risk of developing bladder infections. Also, they are at risk of developing serious kidney infections if bladder infections are not promptly treated. Women who are pregnant should be screened regularly for bladder infections.

Pregnant women should avoid tetracyclines and quinolone (Cipro, levofloxicin/Levaquin, Tequin/gatifloxacin, Avelox/moxifloxacin, more) antibiotics. They should also avoid sulfa drugs (TMP-SMX, trimethoprim/sulfamethoxazole, Bactrim-DS, Septra-DS, more) and Macrodantin (nitrofurantoin) when close to the delivery date.

Some experts recommend that women who frequently experience bladder infections after sexual intercourse take one dose of antibiotic medications to prevent infections. Studies suggest that this approach can prevent bladder infections in certain individuals.

A number of bacteria (germs) can cause bladder infections. Most of the time, physicians can select an antibiotic drug without knowing which type of bacteria is present. Sometimes, however (for individuals such as diabetics who are at risk of resistant infections or for people who have had hard-to-treat infections in the past), physicians will perform a urine test (urine culture) to determine the type of bacteria that is present and which antibiotic will work best against it.