I don't know about you, but if I was suffering, the last thing I'd want to do is start injecting myself with a syringe and needle. If smoking something did the same thing to relieve pain, you can bet I'd throw the needle and syringe the trash. Not only that, look at the expense!
And I don't know about you, but if I was nauseous the last thing I'd want to do is light up a smoke.