Using molecular similarity to highlight the challenges of routine immunoassay-based drug of abuse/toxicology screening in emergency medicine

Table 3 Frequency of prescriptions of target compounds and structurally related drugs for DOA/Tox immunoassays

Immunoassay	Target compound(s) of marketed assays	Highest rank of most prescribed in the United States during 1970s and 1980s¹	Rank as most prescribed in United States in 2007²	Structurally related top prescribed drugs in 2007 and their rank as most prescribed in United States²
Amphetamines	d-Amphetamine d-Methamphetamine³	Top 100 (1970–1971) Top 200 (1970)	66 Unranked	Bupropion (44)
Barbiturates	Secobarbital	Top 50 (1970–1971)	Unranked	Butalbital (163) Phenobarbital (204)
Benzo-diazepines	Diazepam Nordiazepam³ Oxazepam³	1 (1972–1979) Not applicable 93 (1976)	71 Not applicable Unranked	Alprazolam (16) Lorazepam (40) Clonazepam (45) Temazepam (111)
Opiates	Morphine	Top 200 (1970)	230	Hydrocodone (2) Oxycodone (17) Codeine (37) Buprenorphine (248) Hydromorphone (270)
Tricyclic antidepressants	Desipramine Imipramine	Unranked 82 (1972)	Unranked 268	Cyclobenzaprine (47) Amitriptyline (70) Quetiapine (92) Nortriptyline (194) Doxepin (236) Carbamazepine (237) Prochlorperazine (240)

¹ Top prescribed medications in the United States compiled from multiple sources (see Additional file 2).
² See Additional file 1, tab T.
³ d-Methamphetamine is not prescribed but is widely abused. Nordiazepam is not a prescribed medication but is a metabolite of several benzodiazepines (chlordiazepoxide, clorazepate, diazepam, and prazepam). Oxazepam is both a parent drug and potential metabolite of multiple benzodiazepines (chlordiazepoxide, clorazepate, diazepam, prazepam, and temazepam). Imipramine is metabolized to desipramine.

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