Increased catecholamine excretion after labetalol therapy: a spurious effect of drug metabolites |
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| Authors: | L Miano R Kolloch V De Quattro |
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| Affiliation: | Department of Medicine, Los Angeles County/University of Southern California Medical Center and Department of Medicine, White Memorial Medical Center, Los Angeles, CA 90033, U.S.A. |
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| Abstract: | Patients with essential hypertension were treated for four weeks with the alpha- and beta-adreno-receptor blocking agent labetalol. Urinary excretion of total catecholamines, metanephrine plus normetanephrine and vanillylmandelic acid was measured with various methods before and during treatment. An unidentified substance interfering with the fluorimetric method for catecholamines and the photometric assay for metanephrines caused falsely high values of those substances. Using appropriate methodology no changes of total catecholamines, metanephrine plus normetanephrine and vanillylmandelic acid excretion were found after labetalol therapy. Our findings are important in preventing errors in the diagnosis of pheochromocytoma as well as in the evaluation of the effects of labetalol on the sympathetic nervous system in man. |
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| Keywords: | Address for correspondence and reprint requests: Vincent De Quattro M.D. USC School of Medicine 2025 Zonal Avenue Los Angeles CA 90033 U.S.A.. |
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