Patients usually sign a contract stating that they will not divert or misuse narcotics and get them only from the doctor in question and often one other doctor who is available at other times, and also specify a walk-in clinic and/or Emergency Department. This contract has, for CYA purposes, a stipulation that the patient will submit to drugs testing periodically to monitor compliance by showing if there are unapproved controlled substances in the body, or if there is no narcotic in the body, indicating that the patient may have sold or bartered the prescriptions.
Unfortunately, some states are getting into the act and mandating this. Usually it is one test every 5-12 months, with a common thing being having people with a telephone number, patient number, Social Security or national insurance number, or date of birth ending in a given digit to come in during the month so as to have everybody tested every 3, 5, 10 months or whatever; other testing is done for cause, like being intoxicated on something not prescribed or whatever. My doctor in the US did as little as she could get away with respect to this as she knew I was on the narcotics for almost 50 years at that point and never had problems and was never in an addiction type situation . . . so with her patients she would do a urinalysis drugs test with usually a full one to three months heads up (even though she knew that I did not add clandestinely marketed pharmaceuticals, smack, C-Jam or the like, to my regimen or synthesise something myself . . . it was more civil disobedience and her belief that surprising someone with something like that is simply dishonourable. There is a note in my file that will test positive for noscapine, codeine, papaverine, and other alkaloids and she is aware of this and it comes from homeopathic, Ayurvedic, or traditional medicines -- the lab folks usually stopped at the presumptive positive for opiates and that was that; the only reason they go further in any case is a blood and urine test that looks for everything as an adjunct to the endocrine panel and similar tests I get with my annual physical . . . for example, they want to make sure that any of my prescribed medications are not piling up in my system unless that was the idea, and also that the MS-Contin was doing its job without my having shat out a big part of the dose and so on.