I've done quite a few google searches for agents that lower tolerance and you've listed the ones that appear most often. I presume you've done similar searches.
One more search you might want to try if you haven't yet is using clinicaltrials.gov and enter "opioid tolerance".
C4-T4 Scoliosis (disk degeneration, stenosis, narrowed neuroforamen, bone spurs), RT hip and SI joint damage from car accident. Also, pectus excavatum, supraventricular tacycardia and mitral valve prolapse syndrome.
Current meds: Ultram ER 300mg daily, breakthrough - hydrocodone 10-15mg, or oxycodone 5-7.5mg. .25-.5mg ativan as needed for sleep, Verapamil 240mg SR (for tachycardia). [/gray