Tolerance study



Drug-related deaths among people using heroin and/or morphine in the United Kingdom doubled between 2012 and 2015. There is overwhelming evidence that opioid substitution therapy (OST) with methadone or buprenorphine reduces, but does not eliminate, the risk of death especially that resulting from unintentional overdose. OST is a prescription for an opioid medication, similar to heroin, which reduces or removes the need to obtain drugs. Guidelines state that ‘the aim is for people who are dependent on illicit opioids to progress from maintenance [on OST] to detoxification and abstinence’. However, some people may achieve abstinence without OST. Several epidemiological studies have demonstrated that the risk of mortality is heightened on discharge from OST when, it is assumed, users who have lost their tolerance relapse and retake heroin.

After a period of abstinence when relapse occurs, continued heroin use will lead to the development of tolerance. Anecdotally heroin users believe that on relapse the rate and extent to which tolerance develops to the effects of heroin is much greater on recommencing drug use following a period of abstinence (e.g. following detox or incarceration) compared to its development when they first initiated drug use.

It is unknown whether the perception of enhanced tolerance development is subjective/psychological or biological. For example, individuals may be more confident about drug use and take higher doses or expect tolerance to develop and so it does subjectively.

This qualitative research project aims to understand how heroin users who have relapsed following a period of abstinence perceive the development of tolerance to both the euphoric and respiratory depressant effects of opioids.

The knowledge generated will lead to a better understanding of the development of tolerance at different stages of the drug using timeline and may ultimately reveal mechanisms by which tolerance levels could be manipulated (enhanced) to prevent overdose.
Date made available23 Aug 2021
PublisherUniversity of Bristol

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