Blood dyscrasias and carbonic anhydrase inhibitors

Two new cases of aplastic anemia possibly associated with Neptazane (methazolamide) are reported. Several previous authors, as well as the manufacturer of Diamox (acetazolamide) and Neptazane, have recommended routine blood counts for patients on carbonic anhydrase inhibitors. Four surveys are presented of current practices with regard to blood monitoring. These include authors of case reports, 40 academic ophthalmologists, 81 ophthalmologists in private practice, and 66 glaucoma specialists. The vast majority does not routinely monitor blood counts of patients on carbonic anhydrase inhibitors. The value of routine blood monitoring is questionable both because of (1) the idiosyncratic, non-dose-related mechanism of the dyscrasias and (2) the variability of the timing of their onset and development. Regular observation and questioning of patients for symptoms are thought to be preferable. The importance of a thorough history when assigning an etiology to a dyscrasia is noted.