Objective  To evaluate six drug references for their usefulness in identifying over-the-counter (OTC) solid oral dosage forms (SODFs).

Design  Retrospective evaluation of a convenience sample of requests for product identification.

Setting  Drug information center that accepts information requests from health care providers and law enforcement officials throughout the state in which it is located.

Participants  Researchers.

Interventions  Using a convenience sample of 68 nonprescription drugs and 41 dietary supplements obtained from the drug information center's question and answer database, researchers sought to identify the SODFs using six drug-identification online databases.

Main Outcome Measure  Likelihood of identifying a SODF with a given reference, reported as the percentage identified and the corresponding 95% confidence interval.

Results  Overall, 88.2% of nonprescription drugs could be identified using all six references. The highest percentage of nonprescription drugs (77.9%) were identified using Identidex, followed by Ident-A-Drug (67.6%), Drug Identifier (45.6%), RxList (39.7%), Lexi-Drug ID (33.8%), and Clinical Pharmacology (17.6%). Using Ident-A-Drug and RxList together led to the identification of two fewer nonprescription drugs than did Identidex at approximately 5% of the cost. Only 15 (37.5%) of the dietary supplements had an identifying imprint on the dosage form, and 7 (46.6%) of the imprinted products were identified. But overall, only 17.1% (7 of 41) of dietary supplements could be identified, as none of the products without imprints could be positively identified.

Conclusion  Using these six online references, nonprescription drugs could be identified more frequently than could dietary supplements. The lack of imprints on many dietary supplements is an impediment to identification of these products.