Use of acetazolamide in sulfonamide-allergic patients with neurologic channelopathies.

OBJECTIVE To report the safe and successful use of the carbonic anhydrase inhibitor acetazolamide for treatment of patients with episodic ataxia and periodic paralysis who had been denied treatment because of a history of severe allergic reactions to antibiotic sulfonamides. DESIGN Case reports. SETTING University of Rochester Medical Center, Rochester, New York. PATIENTS A 61-year-old man with late-onset episodic ataxia, an 83-year-old woman with mutation-positive Andersen-Tawil syndrome, and a 21-year-old woman with mutation-positive episodic ataxia 2, all of whom had a history of severe skin rash with the use of sulfonamides for treatment of infection. RESULTS The 3 patients had been considered for carbonic anhydrase inhibitor treatment but a pharmacist had refused to fill a prescription for acetazolamide for 1 patient and the other 2 patients were denied treatment because of the allergy history. All 3 patients were prescribed acetazolamide and had no adverse reaction. Two patients improved substantially and are continuing treatment. A review of the pharmacology literature suggests that cross-reactivity between antibiotic and nonantibiotic carbonic anhydrase inhibitors is unlikely. Moreover, a review of case reports does not suggest cross-reactivity. Previous reports in the ophthalmology literature also indicate that acetazolamide can be administered to patients with a history of antibiotic sulfonamide allergic reaction. CONCLUSIONS These 3 cases confirm that the carbonic anhydrase inhibitor acetazolamide can be given to patients with a history of allergic skin rash with antibiotic sulfonamide.