Dried urine spots for detection of benzodiazepines

Benzodiazepines (BZD) are widely prescribed to substance users. However, the nonmedical use of prescription BZD often leads to abuse and dependence. Therefore, it is important to detect BZD among substance users seeking treatment. The aim of the present study was to develop an efficient method for testing BZD on dried urine spot (DUS) and evaluating its clinical applicability.

This involved optimization of conditions for the detection, recovery, and stability of BZD from dried urine, spotted on filter paper. Enzyme linked immuno-sorbent assay was used for screening whereas confirmation was done by gas chromatography. For clinical applicability, urine samples of BZD users were tested.

The recovery was found to be 99.7% in de-ionized water from 20 μl spotted urine samples. Limit of detection, inter-day and intra-day CV were found to be 100 ng/ml, 4.22% and 3.83%, respectively. BZD were found stable in DUS for 3 weeks at room temperature, and for 3 months at 4°C and -20°C. All the urine samples of benzodiazepine users were found positive by conventional method as well as the DUS method.

DUS method proved to be efficient for BZD testing with advantages of ease of collection, transportation, minimal invasiveness and small sample volume. It offers a useful alternative for BZD testing especially in developing countries where logistics of sample collection and transportation could be an important concern.