Which of the following drugs is contraindicated in a patient with history of sulfa allergy presenting with an acute attack of angle closure glaucoma –
First, I need to recall which drugs are used for angle closure glaucoma. Common treatments include beta-blockers, alpha agonists, carbonic anhydrase inhibitors (CAIs), and maybe others. The key here is the contraindication due to sulfa allergy.
Carbonic anhydrase inhibitors come in two types: sulfonamide-based and non-sulfonamide-based. Acetazolamide is a sulfonamide CAI, so it's contraindicated in sulfa allergies. The non-sulfonamide ones, like dorzolamide or brinzolamide, are safer. So if the question is about a drug to avoid, it's probably acetazolamide.
Now, the options aren't listed, but the correct answer is likely acetazolamide. The distractors might include other drugs like beta-blockers (e.g., timolol), which are not contraindicated in sulfa allergy. Alpha agonists like apraclonidine are also used and not related to sulfa. Mannitol is an osmotic agent, not a sulfonamide. So the incorrect options would be the other CAIs or unrelated drugs.
I need to structure the explanation with the core concept about CAIs and sulfa allergies. Then explain why acetazolamide is right, and why others are wrong. The clinical pearl should highlight that sulfonamide CAIs are contraindicated in sulfa allergies. Make sure to keep each section concise and within the character limit.
**Core Concept**
Sulfonamide-based carbonic anhydrase inhibitors (CAIs) are contraindicated in patients with a sulfa allergy due to cross-reactivity. Acute angle closure glaucoma requires rapid intraocular pressure reduction, often involving CAIs like acetazolamide, which is a sulfonamide derivative.
**Why the Correct Answer is Right**
Acetazolamide is a sulfonamide-derived CAI. Patients with a sulfa allergy are at risk of hypersensitivity reactions (e.g., rash, anaphylaxis) when exposed to sulfonamide drugs. Acute angle closure glaucoma necessitates CAIs to decrease aqueous humor production, but acetazolamide must be avoided in this patient population. Non-sulfonamide CAIs (e.g., dorzolamide, brinzolamide) are safer alternatives.
**Why Each Wrong Option is Incorrect**
**Option A:** Timolol (beta-blocker) is not contraindicated in sulfa allergy.
**Option B:** Apraclonidine (alpha-agonist) has no sulfonamide cross-reactivity.
**Option C:** Mannitol (osmotic agent) is unrelated to sulfa allergy.
**Clinical Pearl / High-Yield Fact**
Remember: **"Sulfa allergy = no sulfonamide CAIs."** Acetazolamide is a "sulfa" drug—never use it in confirmed sulfa-allergic patients. Non-sulfonamide CAIs or alternative therapies (e.g., beta-blockers) should be priorit