Is it permissible to use hashish for medical purposes, or to trade it through buying and selling, or to invest in companies that produce and sell it, if it is prescribed by a doctor and approved by pharmaceutical companies?

Consuming hashish and marijuana is forbidden because they are intoxicants and impair the mind, and "whatever intoxicates in large quantities, a small quantity of it is forbidden." Moreover, consuming a small amount of them invites consuming a large amount.

It is permissible to use hashish or other narcotic substances to alleviate pain, provided there is a necessity, no permissible alternative exists, a trustworthy doctor attests to its benefit, its use is limited to the extent of the necessity, and it does not cause greater harm, such as addiction.

As for trading in the shares of pharmaceutical companies that use hashish in some of their products, it is permissible if the company itself is permissible and does not borrow or deposit with usury, because the use of these medications is permissible in some cases due to necessity.