Abstract
We appreciate the comments of Dr. Phillips and Ms. Knowles. They are accurate in pointing out that amprenavir and fosamprenavir should be classified as sulfonylarylamines since these compounds share the same basic structure as sulfanilamide derivatives. Both drugs should be listed under the sulfonylarylamines in Figure 1 of our article with the sulfanilamide derivative antibiotics. Tipranavir was not included in the review since it has not been approved by the Food and Drug Administration.
The clinical information available concerning possible cross-reactivity between these 2 protease inhibitors and other sulfonylarylamines is limited to 2 case series from the manufacturer. 1 These data show that 31% of patients in one group and 37% of patients in another group with a history of a “sulfonamide” allergy or a rash reaction to “sulfonamides” experienced an adverse reaction to amprenavir. However, it was concluded that concurrent therapy with abacavir in 40% of patients in one group and abacavir and/or efavirenz in 76.5% of patients in the other group may have contributed to the adverse reactions.
As discussed in the review, the level of evidence in the case reports of cross-reactivity between sulfonylarylamines and other medications has been poor due in part to inadequate documentation. Future reports can help delineate cross-reactivity more clearly through a concise description of the reaction, the course of events leading to the reaction, and documentation of any diagnostic tests performed.