From the Guidelines
Yes, you can give Lasix to a patient with an allergy to TMP-SMX, as the risk of cross-reactivity is minimal, according to the most recent evidence from 2022. The study published in the Journal of Allergy and Clinical Immunology 1 provides an update on drug allergy practice parameters, which includes information on cross-reactivity between sulfonamide antimicrobials and non-antimicrobial sulfonamides.
Key Points to Consider
- The chemical structure of sulfonamide antimicrobials, such as TMP-SMX, is different from that of non-antimicrobial sulfonamides, like Lasix (furosemide), due to the presence of an aromatic amine group at the N4 position.
- The study suggests that there is minimal concern for cross-reactivity between sulfonamide non-antimicrobials, including loop diuretics like Lasix, in patients with histories of reactions to sulfonamide antibiotics, including TMP-SMX.
- Table XIV from the study 1 lists drugs with no or weak evidence of cross-reactivity in patients with a history of a sulfonamide antimicrobial adverse reaction, which includes loop diuretics like furosemide.
Administration and Monitoring
- When administering Lasix to a patient with a TMP-SMX allergy, it is still important to exercise caution, especially in patients with severe or anaphylactic reactions to TMP-SMX.
- Start with a lower dose of Lasix, such as 20mg orally or IV, and monitor the patient closely for any signs of an allergic reaction, including rash, itching, swelling, or respiratory symptoms.
- If the patient has previously tolerated Lasix without issues, you can continue using it at the appropriate dose for their clinical condition, as the risk of cross-reactivity is considered low based on the evidence from 1.
From the FDA Drug Label
Patients allergic to sulfonamides may also be allergic to Furosemide tablets. The FDA drug label suggests that there may be cross-reactivity between sulfonamides (such as TMP-SMX) and furosemide.
- Key consideration: Patients with a history of allergy to sulfonamides, including TMP-SMX, may be at risk of an allergic reaction to furosemide.
- Clinical decision: It is recommended to exercise caution when administering furosemide to patients with a known allergy to TMP-SMX, and consider alternative treatments if possible 2.
From the Research
Administration of Lasix with TMP-SMX Allergy
- The provided studies do not directly address the administration of Lasix (furosemide) in patients with a TMP-SMX allergy.
- However, it can be noted that Lasix and TMP-SMX are two distinct medications with different mechanisms of action and uses.
- TMP-SMX is an antibiotic used to treat various infections, while Lasix is a diuretic used to treat fluid retention and edema.
- The studies 3, 4, 5, 6, 7 focus on the use of TMP-SMX in patients with allergies or adverse reactions, and do not mention Lasix or its administration in this context.
Considerations for Patients with TMP-SMX Allergy
- Patients with a history of TMP-SMX allergy may undergo desensitization protocols to tolerate the medication, as reported in study 3.
- Alternative prophylaxis options may be considered for patients who cannot tolerate TMP-SMX, as discussed in study 4.
- The decision to administer Lasix in a patient with a TMP-SMX allergy would depend on the individual patient's medical condition and the clinical judgment of the healthcare provider, rather than the allergy itself.