Should Employers Fire Workers for Buprenorphine (Drug for Relieving Opioid Dependency)?

My blog on post-injury drug testing has generated a lively discussion. The consensus view is that this form of drug testing is justified. 

I disagree (as do many but not all courts); but we are moving on to a more specific question.

Should employers fire workers for testing positive for buprenorphine? 
This topic came up in the final year of the Obama administration. OSHA issued a regulation that prohibited blanket, post-injury drug-testing. Instead, it said that employers need what amounted to reasonable cause to drug test after an injury. That rule is not being enforced; and the Trump administration will likely pull it back officially.

Anyway, employers often use a 10-panel screen (there are smaller and larger panels).

Buprenorphine is a common drug test in small and large panels. Basically, it picks out opiate abusers.

But here is the catch: (1) Buprenorphine is prescribed, and not a street drug, and (2) Buprenorphine is used in medication-assisted treatment to help people reduce or quit their use of heroin or other opiates, such as pain relievers like morphine.

Presumably, if an employee tests positive for Buprenorphine, they will be fired. Otherwise, why use the test?

But should an employee be fired because he or she sought professional medical help to be treated for addiction? 
If you need more information, consider the FDA recognized side effects: "Common side effects of SUBOXONE Film include nausea, vomiting, drug withdrawal syndrome, headache, sweating, numb mouth, constipation, painful tongue, redness of the mouth, intoxication (feeling lightheaded or drunk), disturbance in attention, irregular heartbeat, decrease in sleep, blurred vision, back pain, fainting, dizziness, and sleepiness."