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Abstract #6196 Published in IGR 2-2
Monitoring patients taking oral carbonic anhydrase inhibitors
Fraunfelder FT; Grover C; Bagby BAmerican Journal of Ophthalmology 2000; 129: 221-223
Recommendations for hematological monitoring of patients taking oral carbonic anhydrase inhibitors (CAIs) have been a source of conflict and debate. The elements of the current debate include the following: Some feel stopping CAIs probably has no impact on patient outcome, because aplastic anemia is not a treatable disease, so the expense of screening is not justified. Whereas screening has not been prospectively evaluated, aplastic anemia is imminently treatable with either immunosuppressive therapy or early bone marrow transplantation, and earlier treatment (e.g., before blood transfusions) provides better outcomes. Opponents of screening with complete blood counts (CBCs) argue that the rarity of the reaction does not justify the cost and the side-effects of venipuncture. Aplastic anemia as a side-effect of oral CAIs occurs in approximately one in 18,000 patient years of drug exposure, but the disease is so serious that proponents feel the life-threatening nature of the response justifies the expense. Some argue that clinical symptoms of bone marrow failure and abnormal blood counts develop at the same time, so that blood counts are unnecessary; this is incorrect. In fact, there can be a substantial delay between the onset of thrombocytopenia (less than 150,000 platelets/mm3) and spontaneous bleeding (usually at levels of 30,000 platelets/mm3 or less) and between onset of a reduced hemoglobin and symptoms of anemia. Because serious bleeding is uncommon, even in patients with platelets counts of between 20,000 and 50,000/mm3, prophylactic platelet transfusions are usually not warranted, even in leukemic patients, until platelet counts reach 10,000/mm3. Seeking a symptomless 'early window' is precisely the point of screening. There is concern that publication of 'guidelines' is tantamount to a medico-legal mandate. This issue is difficult to address. No prospective studies have been carried out, so no guidelines can be firmly evidence-based. Proponents of screening are better advised to characterize their strategy as 'an alternative view' rather than guidelines in the 'evidence-based' sense.
Dr. F.T. Fraunfelder, Casey Eye Institute, 3375 SW Terwilliger Boulevard, Portland, OR 97201, USA
Classification:
11.5.1 Systemic (Part of: 11 Medical treatment > 11.5 Carbonic anhydrase inhibitors)
