No, Eddie, the legislation i exactly as I quoted in may earlier post: "...unfit to drive through drink or drugs... "
Your point about being impaired as a result of taking legal or prescription drugs is interesting. But I believe the law is quite clear. If taking a quantity of cough medecine made you (say) drowsy and unable to react properly your driving would be impaired and it would be as a result of taking drugs (the cough jollop).
To secure a conviction under this section of the RTA the prosecution must prove:
To secure a conviction, the Crown must prove:
1.That a person was unfit to drive;
2.Through drugs; and
3.His driving was impaired.
Again, no mention of whether the drug is "legal" or not. Section 11 of the RTA provides interpretations for the earlier sections. It says:
"'drug' includes any intoxicant other than alcohol...
In the case of Armstrong v Clark it was held that "...a substance used as a medicine is a drug, something to cure, alleviate or assist an ailing body."
Therefore, Codeine, Asprin or Ibroprofen are classed as drugs and if their effects result in impaired driving an offence will be committed.