List of sulfa drugs.
A sulfa drug is any medication carrying the sulfonamide group –SO2NH2. Dozens of drugs qualify, but they do not all matter equally to someone with a sulfa allergy. The list below is split by the feature that actually predicts cross-reaction: whether the molecule also carries an arylamine at the N4 position. Sulfa antibiotics do. Almost nothing else does.
Educational reference — not medical advice. This page describes what is generally known about a drug family. It cannot account for your history, your other medicines, or your circumstances. Decisions about your own treatment belong with your doctor or pharmacist.
- The short answer
- If someone says "sulfa drug" without qualification, they mean a sulfa antibiotic — most often
sulfamethoxazole/trimethoprim(Bactrim, Septra). - The dividing line
- The N4 arylamine. Present in sulfa antibiotics and sulfasalazine; absent in the diuretics, sulfonylureas, celecoxib, and the carbonic anhydrase inhibitors.
- Why it matters
- An allergy label earned from a sulfa antibiotic does not automatically rule out the drugs in the second table. Cross-reactivity is low.
Group 1: sulfa antibiotics (arylamine-bearing)
These are the drugs that carry essentially the whole allergy burden. They carry the N4 arylamine, which the body oxidises to a reactive nitroso metabolite that binds to host proteins and provokes a drug-specific T-cell response. That pathway is well characterised, and it is the part of the structural argument that the evidence actually supports. (These drugs also share an N1 heterocyclic ring, sometimes proposed as the target of IgE-mediated reactions, but that is a hypothesis rather than a demonstrated mechanism.)
| Drug | Common brands | Used for |
|---|---|---|
| Sulfamethoxazole / trimethoprim | Bactrim, Septra, co-trimoxazole | UTI, MRSA skin infection, PCP prophylaxis, travellers' diarrhoea |
| Sulfadiazine | — | Toxoplasmosis (with pyrimethamine), rheumatic fever prophylaxis |
| Silver sulfadiazine (topical) | Silvadene, Flamazine | Burn wound care |
| Sulfacetamide (topical / eye) | Bleph-10, Klaron | Bacterial conjunctivitis, acne, seborrhoeic dermatitis |
| Sulfadoxine / pyrimethamine | Fansidar | Malaria (limited, region-specific use) |
| Sulfisoxazole | Gantrisin | Largely withdrawn; historical UTI agent |
| Sulfasalazine | Azulfidine, Salazopyrin | Ulcerative colitis, rheumatoid arthritis — not an antibiotic, but metabolised to arylamine-bearing sulfapyridine |
sulfapyridine, and sulfapyridine carries the same arylamine as the antibiotics. People with a genuine sulfa antibiotic allergy may react to it. More on sulfasalazine.
Group 2: non-antibiotic sulfonamides (no arylamine)
Every drug below contains a sulfonamide group, which is why drug-interaction checkers and older references flag them against a "sulfa allergy." None of them carries the N4 arylamine. Published cross-reactivity rates are low, and most prescribers will use these drugs in a patient whose sulfa allergy came from a typical antibiotic rash.
| Class | Drugs | Used for |
|---|---|---|
| Loop diuretics | Furosemide (Lasix), bumetanide, torsemide | Heart failure, oedema |
| Thiazide & thiazide-like diuretics | Hydrochlorothiazide, chlorthalidone, indapamide, metolazone, chlorothiazide | High blood pressure, oedema |
| Sulfonylureas | Glipizide, glyburide (glibenclamide), glimepiride, gliclazide, chlorpropamide, tolbutamide | Type 2 diabetes |
| Carbonic anhydrase inhibitors | Acetazolamide (Diamox), methazolamide, dorzolamide, brinzolamide | Glaucoma, idiopathic intracranial hypertension, altitude sickness |
| COX-2 inhibitor | Celecoxib (Celebrex) | Arthritis, pain |
| Triptans | Sumatriptan, naratriptan | Migraine |
| Anticonvulsant | Zonisamide | Epilepsy |
| Antiarrhythmics | Sotalol, dofetilide, ibutilide | Atrial fibrillation and other arrhythmias |
| Alpha-blocker | Tamsulosin | Benign prostatic hyperplasia |
| Endothelin antagonists | Bosentan, macitentan | Pulmonary arterial hypertension |
| HIV protease inhibitors | Darunavir, fosamprenavir, tipranavir | HIV treatment |
| Uricosuric | Probenecid | Gout |
Frequently mistaken for sulfa drugs
Several drugs and substances end up on informal "avoid with sulfa allergy" lists without belonging there.
| Substance | What it actually is |
|---|---|
| Dapsone | A sulfone, not a sulfonamide — a different chemical class. The 2022 AAAAI/ACAAI practice parameter groups it with the drugs of minimal cross-reactivity concern after a sulfa antibiotic reaction. Its bigger issue is haemolysis in G6PD deficiency, which is why pre-prescription testing is standard. |
| Topiramate | A sulfamate ester. Related but structurally distinct from a sulfonamide. |
| Sulfites | Food and drug preservatives (wine, dried fruit, some injectables). Chemically unrelated to sulfa drugs. |
| Sulfates | Inorganic salts — magnesium sulfate, ferrous sulfate, sodium lauryl sulfate. Unrelated. |
| Elemental sulfur | The element, including sulfur-containing amino acids in food and sulfur in acne preparations. Unrelated. |
| Penicillins and cephalosporins | Beta-lactams. They contain a sulfur atom in the ring, which is not the same as a sulfonamide group. A sulfa allergy does not imply a penicillin allergy. |
The overlap in names does real damage. Patients decline wine, avoid magnesium supplements, or refuse an antibiotic they could safely take, all on the strength of three shared letters. The disambiguation page works through each one.
How to use this list
The list identifies what contains a sulfonamide group. It does not tell you what is safe for you — that depends on what your original reaction actually was, how severe it was, and what alternatives exist for the condition being treated. If your record says "sulfa allergy" and you do not know the drug, the year, or the reaction, that is worth resolving: it is the single detail that determines how much of this list is genuinely off-limits. How to describe your allergy usefully, and how mislabelled allergies get removed.
References
- Khan DA, Banerji A, Blumenthal KG, et al. Drug allergy: a 2022 practice parameter update — Table XIV, drugs with no or weak evidence of cross-reactivity. J Allergy Clin Immunol. 2022;150(6):1333-93. www.jacionline.org
- Giles A, Foushee J, Lantz E, Gumina G. Sulfonamide allergies. Pharmacy (Basel). 2019;7(3):132. pmc.ncbi.nlm.nih.gov
See also
- Sulfa antibioticsThe group that carries the allergy burden, in detail.
- Cross-reactivity: what the evidence showsWhy group 2 is usually safe for group 1 reactors.
- Antibiotic vs non-antibiotic sulfonamidesThe arylamine, explained properly.
- Common cross-reactivity questionsBactrim with HCTZ, Lasix, Celebrex — one drug at a time.