Evaluation of a Compliance Marker in Prescription Opioid Abusers With Chronic Pain

In a small, well-characterized sample of prescription opioid abusers (POAs) with chronic pain and on buprenorphine therapy, this supplement study will investigate the utility and feasibility of two novel tracer compounds, and in combination with a standard marker (riboflavin), to monitor adherence to study drug prescription in the parent clinical trial (NCT01821430). 1. We will examine the ability of two benign (in the doses used) medications, quinine (80mg) and acetazolamide (15mg) to serve as valid and reliable markers of medication use. The relative utility of each will be described for use with the study medication (PGB 400mg/day), a drug dependent on primarily renal excretion. In that both PGB and acetazolamide are eliminated unchanged in the urine, we will examine if the latter can be used without altering the elimination rate of the former, or whether a maker with both hepatic and renal modes of elimination (quinine) would serve as a better indicator of adherence in the trial. 2. Being a standard in clinical trials, the medication adherence marker riboflavin is used in the parent study (NCT01821430), as it can be readily detected in urine samples by simple visual inspection. However, riboflavin is a relatively gross indicator of medication use; it does not reside in the body for the time period typically required in outpatient trials, can be affected by dietary riboflavin and has variable absorption. Capitalizing on riboflavin's ease of detection, the second aim of this supplement will be to examine whether riboflavin when combined with one of the new candidate tracers, can provide a superior indicator of adherence, in that riboflavin can be qualitatively observed immediately, and the other tracer being quantitatively detected during subsequent urine toxicology analyses. The cross over design of the study will allow us to address these aims in an efficient and straightforward manner. Following examination of the pharmacokinetics (PK) of PGB alone, it's PK will then be reexamined when compounded with acetazolamide, and again with both acetazolamide and riboflavin present. Next, after a short washout period, the studies PGB PK will be repeated with acetazolamide replaced by quinine. If the new tracers do not interfere with the PK of PGB, one of them will be chosen to be formulated (along with riboflavin) with PGB for use in the parent study, thereby providing both qualitative and quantitative indicators of adherence.