Drug Profile

Both sulfisoxazole and trimethoprim with sulfamethoxazole (BACTRIM, BACTRIM DS, SEPTRA, SEPTRA DS, SULFATRIM PEDIATRIC) are drugs from a class called sulfonamides, or sulfa drugs.

Sulfisoxazole is used to treat urinary tract infections and some other infections. Patients with kidney or liver damage should take less than the usual adult dose. Sulfisoxazole will not help a cold or the flu.

Sulfisoxazole is available in several forms. It is often taken by mouth. Another form of the drug, a vaginal cream, is used to treat vaginitis, but there is no evidence that this is an effective treatment. For eye infections, there are ointment and solution forms of sulfisoxazole that are similar to sulfacetamide.

Trimethoprim with sulfamethoxazole is a combination of the synthetic antibacterial trimethoprim and the sulfa drug sulfamethoxazole. This combination of drugs is commonly used to treat urinary tract infections but also is approved to treat bacterial infections in other parts of the body.

Adverse effects

A certain type of skin rash called fixed pigmentation erythema has been associated with the use of trimethoprim with sulfamethoxazole. This rash is accompanied by inflammation and leaves the skin pigment permanently darkened.[1]

Deaths have been associated with the use of sulfonamides due to severe skin reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis), serious allergic reactions, liver toxicity and bone marrow toxicity. Products such as trimethoprim with sulfamethoxazole should be discontinued at the first appearance of skin rash or any sign of an adverse reaction.[2],[3]

In November 2014, Health Canada, an agency similar to the FDA, announced that a safety review of sulfamethoxazole and/or trimethoprim containing products revealed a potential risk of a condition in which there is a low number of blood platelets (platelets prevent bleeding). This condition also had been reviewed by the FDA, and changes were made to the product labeling in 2012.[4]

Trimethoprim has been linked to birth defects, including spinal cord abnormalities, cleft palate and heart malformations, in children born to women who used trimethoprim during the first trimester.[5] Some of these defects likely are due to the drug’s ability to interfere with folic acid.

Interactions

In September 2011, the British Medical Journal (BMJ) released the results of important research showing that elderly patients prescribed trimethoprim with sulfamethoxazole in combination with the diuretic spironolactone (ALDACTONE) have a much higher risk of being hospitalized for hyperkalemia (increased levels of potassium in the blood). The risk of hospitalization due to hyperkalemia for elderly patients in the study, all of whom were also taking spironolactone, was much greater for those taking trimethoprim with sulfamethoxazole than for those taking either amoxicillin (AMOXIL, AUGMENTIN, LAROTID, MOXATAG) or nitrofurantoin (FURADANTIN, MACROBID, MACRODANTIN). (Read more in the December 2011 Worst Pills, Best Pills News.)

In October 2014, another study in the BMJ showed that two classes of medications used to treat high blood pressure, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), when used in combination with the antibiotic trimethoprim with sulfamethoxazole, can increase blood potassium levels and can increase the risk of sudden death, most likely due to abnormal heart rhythms.[6] (Read more in the June 2015 Worst Pills, Best Pills News.)

In October 2014, JAMA Internal Medicine published a study showing that older patients taking one of two commonly used oral sulfonylurea diabetes drugs — glipizide (GLUCOTROL, GLUCOTROL XL) or glyburide (DIABETA, GLUCOVANCE, GLYNASE) — in combination with trimethoprim with sulfamethoxazole had an increased risk of developing dangerously low blood sugar levels, a condition known as hypoglycemia.[7] (Read more in the November 2014 Worst Pills, Best Pills News.)

Preventing urinary tract infections

Practice measures to prevent urinary tract infections. Drink plenty of fluids, especially water. (Although cranberry juice is unreliable as a cure for urinary tract infections, the juice may reduce odor from incontinence.[8]) Practice meticulous hygiene. For women, after using the toilet, wipe backward, not forward, then wash hands. Prepare and store foods properly, especially when traveling, to prevent diarrhea. Restrict caffeine, which widens the urethra.

Indwelling bladder catheters invite urinary tract infections. However, unless there are symptoms of a urinary infection, it is not always necessary to take medication just because bacteria are found in a urine test.[9]

Women are particularly prone to repeated urinary tract infections. If urinary tract symptoms occur often, ask a doctor about keeping a supply of medication on hand. Ideally, the antibiotic used should be the most effective, least toxic and least costly.[10],[11]