Can You Take Lasix If You Are Allergic To Sulfa?
In our latest question and answer, our pharmacist discusses whether or not furosemide is safe to take if you have a sulfa allergy.
Hello! My mom is allergic to sulfa. Should she be given Lasix? The last time she took Lasix, she had severe dizziness and vomiting.
Jan 11, 2023- Lasix contains a sulfa component, so there is a theoretical risk of an allergic reaction if you have a sulfa allergy, though studies show this risk is relatively low.
- You should discuss your sulfa allergy history with your doctor, who can decide whether Lasix is safe for you or if a non-sulfa diuretic would be a better option.
- If you and your doctor decide to use Lasix despite a sulfa allergy, close monitoring while taking the medication is important.
Answer
Thanks for reaching out to us! Evidence is mixed regarding whether or not having a 'sulfa' allergy precludes you from being able to take Lasix (furosemide).
If you take a look at the chemical structure of Lasix, you will see that it contains a sulfa moiety, as shown in the picture below:
Since furosemide does contain a sulfa element, there is a theoretical risk of cross-sensitivity in those who have an allergy to sulfa antibiotics. The prescribing information for furosemide warns as much:
Patients allergic to sulfonamides may also be allergic to furosemide.
What Is The Risk?
As mentioned, evidence is mixed regarding how likely someone who has a 'sulfa' allergy is to be allergic to furosemide as well.
Some studies conclude that there is essentially no risk while others warrant caution.
Overall, it appears that there is a relatively low risk of cross-sensitivity, but there certainly are at least a few published case reports that have detailed individuals who have a documented history of a sulfa allergy who were also believed to have suffered an allergic reaction to furosemide or similar 'sulfa' containing drug (that was not an antibiotic).
Having read through multiple studies on the matter, I believe an excerpt from one sums the situation up nicely:
This case and the literature review I did for it illustrate that, although cross-reactivity between sulfa antibiotics and nonantibiotics is rare, certain situations warrant prudence.
You should speak with your doctor regarding your history of allergic reactions (or your mother in this case), and discuss what the best treatment options are for the specific medical situation.
There are plenty of non-sulfa-containing diuretics available (such as amiloride, eplerenone, spironolactone, etc...) that could be options. If you, your mother, and the doctor decide that furosemide represents the best course of therapy, again, the risk of having an allergic reaction to it based on its sulfa component is low, but the individual taking the drug should nevertheless be monitored closely while taking it.
Final Words
I hope you found this answer helpful. Please reach back out anytime!
References & sources
- Furosemide Prescribing Information — AccessFDA
- Cross-Reactivity Between Sulfonamides and Loop or Thiazide Diuretics: Is it a Theoretical or Actual Risk? — PubMed
- [Cross allergy between sulphonamide diuretics, probenecid, sulphamethoxazole and sulphonyl-urea compounds (author's transl)] — PubMed
- Approach to managing patients with sulfa allergy — PubMed
- Use of furosemide and other sulfonamide nonantibiotics in patients with sulfa allergy — JAPHA
- Which diuretics are safe and effective for patients with a sulfa allergy? — MDedge
Glossary — Terms in This Answer
- Sulfa moiety
- A chemical component containing sulfur that is part of a drug's molecular structure.
- Cross-sensitivity
- The chance that an allergic reaction to one substance will occur when exposed to a similar substance.
- Sulfonamides
- A group of drugs containing a sulfa chemical structure, often used as antibiotics.
- Cross-reactivity
- An allergic or immune reaction that occurs to a different drug or substance due to its similarity to one you're already allergic to.
- Diuretics
- Medications that help remove excess water and salt from the body by increasing urine production.
- Furosemide
- A loop diuretic medication (brand name Lasix) used to remove excess fluid from the body in conditions like heart failure and high blood pressure.
- Amiloride
- A potassium-sparing diuretic medication that helps remove water from the body without affecting potassium levels.
- Spironolactone
- A potassium-sparing diuretic medication that blocks aldosterone to help remove excess water and salt.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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