The DRI Amphetamines assay is intended for the qualitative or semi-quantitative determination of amphetamine and methamphetamine in human urine.
The DRI® Amphetamines assay is a liquid ready-to-use homogeneous enzyme immunoassay. The assay uses specific antibodies, which can detect amphetamine and/or methamphetamine in urine with minimal cross-reactivity to various over-the-counter structurally unrelated compounds. The assay is based on the competition of an enzyme glucose-6-phosphate dehydrogenase (G6PDH) labeled drug and the drug from the urine sample for a fixed amount of specific antibody binding sites. In the absence of free drug from the sample, the specific antibody binds the drug labeled with G6PDH and causes a decrease in enzyme activity. In the presence of free drug, the free drug occupies the antibody binding sites, allowing the drug labeled G6PDH to interact with the substrate, resulting in enzyme activity. This phenomenon creates a direct relationship between drug concentration in urine and the enzyme activity. The enzyme activity is determined spectrophotometrically at 340 nm by measuring its ability to convert nicotinamide adenine dinucleotide (NAD) to NADH.