Table 3.

Experimental validation of cross-reactivity, including parent drugs and metabolites.^a

Screening assay	Compound tested	Parent drug	Concentration causing a presumptive positive, μg/mL
Amphetamines	α-Methyldopamine	Methyldopa	13.6
	Procainamide	—	23.2
	Ceftaroline fosamil	—	53.1
	N-acetyl-3-hydroxyprocainamide	Procainamide	92.2
	Imatinib	—	216.6
	Esmolol	—	237.3
	Esmolol acid	Esmolol	446.4
	Methyldopa	—	NA
	3-o-Methyldopa	Methyldopa	NA
	Donepezil	—	NA
	6-o-Desmethyldonepezil	Donepezil	NA
Buprenorphine	Rotigotine	—	0.13
	Trimethoprim	—	47.2
	Procainamide	—	92.8
	N-acetyl-3-hydroxyprocainamide	Procainamide	126.2
	Propafenone	—	180.7
	Ceftaroline fosamil	—	681.5
	Donepezil	—	709.6
	Sulfamethoxazole	—	NA
	Cytarabine	—	NA
Cannabinoids	Raltegravir	—	339.5
	Rotigotine	—	415.1
Methadone	Propafenone	—	83.2
	Pazopanib	—	198.4

^aNA indicates the compound was not sufficiently cross-reactive to cause a presumptive positive on the given screening assay at the concentrations tested. Cytarabine was not expected to be cross-reactive. In addition, based on the EHR data analysis, the potential cross-reactivity of trimethoprim and sulfamethoxazole could not be distinguished.