What Are The Damages One Could Face Due To Long Term Use Of Heroin/cocaine?

What may be the issue if one is a daily user of IV Heroin + Cocaine (in the same syrtinge, at the same time), who generally experiences a rise in heartrate (from 75-80 resting) to 125-160 post injection, like clock-work, then one day starts to experience no significant increase whatsoever from the same dose? The medication metoprolol @ 25mg/day is taken, too. Tolerance to the substances is most certainly not the cause, as such vitals and patterns of vital changes monitored over the course of eight years have shown that [tolerance] seems not to be the main issue. At what immediate risks would be this person. Other medications include a TCA, bupropion, lorazepam and amantadine. Patient details follow: Approx. 30 years of age, 67" height, and weight near 200lbs; No medical history outside of psychiatric and orthopaedic in nature. Thank you.