How can i increase non existent sex drive after years of substance misuse?

Seek sex therapy: I would start by with working w a qualified sex therapist. You could go on some websites like aasect or ssss and see if there is someone in your area to consult with.

Time in recovery: If you are on subutex, it is likely that you are in some type of recovery program and/or attending 12 step or other support meetings. Work on your recovery and stay clean & sober for a while, and your interest in many things will come back, including sex. You may want to ask whomever is prescribing the subutex if its opiate blocking properties may be part responsible too.