Narcotic Substances

Answer – and Allah is the One who grants success: Of narcotic substances, whatever acts upon a person in the manner of wine is prohibited; whatever is like that is, in ruling, wine, and is called “wine” in the Sacred Law, as it has been established that “every intoxicant is wine.”
Likewise, of narcotic substances, whatever harms a person’s health is prohibited. It is well known that narcotic substances, in general, harm the person and destroy his health, and that using them involves extreme danger. It has become widely known in the world that the disease of AIDS is among the consequences of using narcotics.
And it is well known today that narcotics are more harmful than wine. It is among the agreed principles with rational people that whatever’s harm and corruption outweigh its benefit and advantage is prohibited.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2