From the FDA Drug Label
Sulfamethoxazole and trimethoprim is contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides The answer is: sulfa allergy is a contraindication to TMP-SMX use 1.
From the Research
A sulfa allergy is a contraindication to Trimethoprim-Sulfamethoxazole (TMP-SMX) use. Patients with known hypersensitivity to sulfonamide antibiotics should not receive TMP-SMX due to the risk of severe allergic reactions, which can range from skin rashes to life-threatening conditions like Stevens-Johnson syndrome or toxic epidermal necrolysis, as noted in a study published in 2024 2. The sulfamethoxazole component of the medication is responsible for these allergic reactions in susceptible individuals. If a patient reports a sulfa allergy, alternative antibiotics such as nitrofurantoin, fluoroquinolones, or beta-lactams should be considered depending on the infection being treated. It's essential to document this allergy clearly in the patient's medical record. Some studies have explored the concept of desensitization for patients with a history of sulfonamide adverse reactions, showing that graded administration of TMP-SMX can be safe and effective in both HIV-infected and non-HIV infected patients 3, 4. However, these procedures should be undertaken with caution and under close medical supervision. Neither BMI greater than 30, suprapubic pain, nor vaginal discharge are contraindications to TMP-SMX therapy, although these factors might be relevant to the underlying condition being treated or might influence medication dosing considerations. The use of TMP-SMX has been well established for various infections, including its role in prophylaxis against opportunistic infections in immunosuppressed patients, as discussed in recent medical literature 2.