I have no clue about this, but I would say, as 8 hours of fasting from eating anything is recommended before the SN, I presume cleansing your body of any other chemicals would also ensure a more effective usage of SN.
This being said... if you are receiving a dose of such medication, it means you have a medical condition. This being the case, know that medications are extremely powerful, and many have changed their lives thanks to them. I would reccomend you, with all my heart, to clean your mind of such suicidal thoughts, and to hide your SN away from your eyes for now. Give the medication a chance, an honest chance, focus your mind on that hope that it'll help you to see the light at the end of this tunnel.
If it all fails, SN will always be there for you, and we will be here, supporting you each step of the way, whichever decision you take, whichever path you decide to go for.
Best of luck my friend, and I am certain that, whatever decision you take, you'll find peace.