Over on the Brown and Little law firm 'blog, Matt Brown remarks that according to ARS 28-1381, one can be driving under the influence without being impaired, simply by having any drug defined in ARS 13-3401 or its metabolites in one's body.
ARS 13-3401 is a guide to searching Wikipedia for designer drugs and perhaps half the syllabus for a nontraditional course in pharmacology. Name a hallucinogen, narcotic, or controlled stimulant or depressant, and you'll find it listed.
Included are a number of prescription drugs which may or may not produce impairment depending on the dosage, including Valium and several of the more common muscle relaxants, and some that produce no impairment at all, such as Ritalin, scopolamine (administered transdermally as an anti-emetic) and most anti-narcolepsy drugs, without which some drivers will find themselves impaired. There's quite the list of amphetamines, some of which are commonly given to Air Force pilots to keep them alert on very long missions.
And then there is that pharmacologically valuable but illegal substance, cannabis, very curiously classified as a narcotic. Under normal use does not impair the motorist, hence the original post. Its inclusion presents problems for users of legal Marinol, an anti-emetic inhaler, as its active constituent is a purified cannabis derivative. By spliff or by inhaler, the metabolites are indistinguishable.
But most problematic are twenty-three "anabolic steroids", classified as "dangerous drugs". Many are endogenous or have endogenous metabolites. Some are common medications for very serious conditions: oxandrolone is a treatment for osteoporosis and HIV-related weight loss, and testolactone is a very valuable chemotherapeutic agent against breast cancer. None conceivably produce impairment, but my "significant other" as they say might remark that testosterone impairs judgement. That's right, testosterone is on the list. It's in your body and mine--whether you're male or female--along with its metabolites. Thus according to ARS 28-1381, we're all driving under the influence.
In Arizona, if you're being treated for ADHD, ADD, narcolepsy, hyperemesis (including that induced by cancer chemotherapy), some forms of breast cancer, or HIV-related weight loss, you're driving under the influence. But you're not alone: all men, and any woman who hasn't had a hysterectomy, also run afoul of the law. It's simply unlawful to drive in Arizona.