Prescribing toxic smoke

(A letter in the Letters section of the Globe and Mail, A10, March 25, 2014):
Rx for pot plants
Re Wary Doctors Pressed into Prescribing Medical Pot (March 23):  There are good reasons why doctors are reluctant to prescribe marijuana. These include all the problems with prescribing whole plants as medicines, including the thousands of other chemicals delivered in addtion to the intended active ingredient, variations in the potency of the active ingredient, making accurate dosing impossible, and issues of purity.

There is no reason to think smoking marijuana is any safer than smoking tobacco. If used at all, marijuana plants should be consumed only orally (for example, in brownies).

Evidence for the benefit of marijuana is limited; belief, no matter how strongly held, does not qualify as evidence.

There are pure, properly tested drugs containing the active cannbinoid ingredients of marijuana, and those may be reasonable candidates for prescription.

Prescribing whole plants for the purpose of smoking them cannot be regarded as a reasonable thing to ask of physicians. 
- J. David Spence, MD, professor of neurology and clinical pharmacology, Robarts Research Institute