Medications that may interfere with biochemical testing - McMaster Textbook of Internal Medicine

Table 6.1-2. Medications/substances that may interfere with biochemical testing
	Normetanephrines		Metanephrines
	Plasma	Urine	Plasma	Urine
Acetaminophen	↑↑	↑↑	No change	No change
Labetalol	No change	↑↑	No change	↑↑
Sotalol	No change	↑↑	No change	↑↑
Alpha-methyldopa	↑↑	↑↑	No change	No change
Tricyclic antidepressants	↑↑	↑↑	No change	No change
Phenoxybenzamine	↑↑	↑↑	No change	No change
Monoamine oxidase inhibitors	↑↑	↑↑	↑↑	↑↑
Sympathomimetics	↑	↑	↑	↑
Levodopa	↑	↑↑	↑	↑
Buspirone	No change	No change	↑↑	↑↑
Cocaine	↑↑	↑↑	↑	↑