Yes a form of Sulfa. Lasix (furosemide) does have sulfa in it but it is a form of sulfa often tolerated by those with sulfa allergy. Sulfa medications fall into two major chemical formats and one form is much less allergenic. As opposed to sulfa antibiotics which many are allergic to, this other form includes lasix, thiazide, migraine medication imitrex, non-steroidal anti-inflammatory celebrex, (celecoxib) and diabetes: diabeta.
Lasix (furosemide) is a waterpill. Diuretics (water pills).The risk for sulfa-containing diuretic pills causing reactions in sulfa-allergic patients is low. Many diuretic medications, such as furosemide (Lasix) are from a chemical formula that is related to sulfa medicines "sulfa-based".While there is no proof that people with an allergy to sulfa-based antibiotics will also react to sulfa-based non-antibiotics, like Lasix, it could.