Is it ethical to deny a possible cure to patient?

Medical ethics can be summarized to "Do no harm, do good always" beneficence/non-maleficence.

Say if there is a possible cure but doctors can't/won't prescribed it. Is it ethical? This violates beneficence. 

What if the cure is an illegal drug? Illegal drugs which if abused, is lethal.

A grey area. But it is frustrating for someone like me.

I have PTSD and one of the promising cure is LSD. Doctors would say it is non-maleficence for not prescribing the 'allegedly' dangerous drug. Patients are frustrated because we have to deal with it. Doctors should have the PTSD experience to understand, not just blabbing, recommending CBT and such. Prescribing the stupid SSRIs which can induce suicide.

Why not take the risk with PTSD? We want cure!

SSRI the standard regimen is not 100% safe. Suicide, hypertension and even withdrawal is a pain in the ass. I gained weight too.

LSD isn't the angel but compared to the risk possessed by SSRIs, why not? Both have it's own risks.
We endured enough, we don't mind taking risk.

Sometimes, medicine is stupid. The cure is there but 'illegal'.

Legalize LSD for medical purposes!