Does smoking drugs degrade them?

Question

Why doesn't smoking a drug degrade or destroy it?

A wide variety of psychoactive compounds ("drugs") are commonly consumed via smoking – e.g., nicotine, THC, amphetamines, cocaine, and DMT. But in every case, the desired drug is present in the uncombusted source, and AFAIK the potency of any of these organic compounds is not enhanced by either heat or oxidation. (Indeed, when possible users seem to prefer inhaling vaporized or powdered distillates to inhaling smoldering compounds.)

So how do these drugs survive smoking? I'm guessing that either (a) the drugs resist oxidation at the combustion temperatures of their carrier compounds, or (b) some fraction does oxidize. I'm also suspecting that the chemistry of "smoking" might be quite different from the chemistry of efficient combustion.

Answer 1

Smoking volatilises active compounds but may also degrade them

Many active ingredients in drugs are volatile alkaloids readily absorbed through the mucus membranes in the mouth, nose, and lungs. Nicotine, THC, and heroin are good examples of varying legality.

The reason why smoking is often used to deliver them is that smoking is a convenient way to deliver the volatile active ingredients into the body. Sure, burning will degrade some of the active ingredients in a cigarette, but burning the tip of the cigarette causes hot air to be drawn through the unburnt portion of the device which releases the volatile active ingredients in the unburnt part. This is convenient, though dangerous as many of the less desirable contaminants are also created as a side effect of burning. This is why cigarettes kill: it isn't the desired nicotine but the side effects of burning and the other, undesirable, ingredients that are also released in the volatilisation process. And, burning may destroy some of the active ingredients (though most users will get enough for this not to matter much).

This is also why electronic cigarettes can deliver nicotine relatively uncontaminated by those other products and are, often, effective substitutes for getting nicotine into addicts far more safely than via burning sticks of tobacco (the process of controlled heating can volatilise relatively pure nicotine without the side effects of less controlled burning and the source can be far purer than tobacco leaf).

Similar considerations apply to other active ingredients.

So, the bottom line is that, yes, burning is usually bad but mostly because it is not a very controlled way to deliver active ingredients. We use it because it is convenient and easy despite its drawbacks.

Answer 2

Fire or burning does not distinguish if organic matter is a drug or not.

Depending on organic substance nature

• some of it evaporates or sublimes,
• the rest is thermally converted and finally eventually burnt.

Answer 3

Note that most things in this world do not burn instantly, and those that do are usually useless as drugs(imagine smoking aluminium powder). You need some time.

Therefore, e.g. if you smoke a cigarette for 3 minutes, the 3 minutes are just too short for 'all' the nicotine to burn away(= 'some' of the nicotine just gets vaporised and ends up in the smoker's body), and hence cigarettes are not available to those under 19 because that 'some' small amount of nicotine is still harmful to minors.