The quantitative evidence presented within this study demonstrates, first and foremost, that dose satisfaction is an important consideration in the provision of iOAT, as has been found with dose adequacy in other forms of OAT.(10, 11, 44)This is clear from many of the findings of this study, but perhaps most obviously it is shown via participants who, when they aren't satisfied with their dose, are also more likely to report being troubled by problems related to criminalized drug use—even after controlling for other relevant factors. One of the main goals of all treatment for OUD is to reduce clients’ problems from/with criminalized drug use, which can stem from frequency of use of the drugs themselves, but also from issues associated with obtaining criminalized drugs (and the money required to buy them), and how/when/where/with whom criminalized drugs can be used. This inherent complexity is reflected in the finding that clients’ perception of troubles from criminalized drug use has a stronger association with dose satisfaction than actual frequency of criminalized opioid (“heroin”) use. Further, feeling "troubled by problems" can likely be considered a proxy for stress levels, and higher levels of stress are a known predictor of dropout from OUD treatment,(45) meaning this is a particularly vulnerable group of clients in multiple ways.
Whether clients are smokers or not also emerged as a strong predictor of dose-satisfaction status, which could have several explanations. These include (but aren't limited to): greater tolerance to the euphoric effects of opioids (at least partly from down-regulation of dopamine response in general, one cause of which is a response to frequent dopamine activation by consistent administration of drugs,(46) including nicotine), to increased stress levels from inadequate dosing and increased withdrawal symptoms. Since stress is a principal factor promoting tobacco use,(47) inadequate dosing would make it less likely that those participants would be empowered to choose—and succeed in—managing, reducing, or quitting smoking. Adequate dosing is an inherent part of effective treatment,(48) and participants who smoke tobacco and/or who experienced more troubles from problems associated with criminalized drugs were more likely to also be receiving an inadequate dose, and therefore inadequate treatment.
Our results also indicate that iOAT clients’ perception of their doctors involving them in decisions (i.e. sharing decision-making power) was significantly associated with clients’ dose satisfaction status in both unadjusted modelling and when first introduced to the stepwise adjusted model. That this association is eventually eclipsed by the addition of the “drug liking” variable suggests that the latter is accounting for some of the variability otherwise explained by the shared decision-making variable. Straightforwardly: clients who like the drug they’re receiving are more likely to feel satisfied with the dose, whereas clients who don’t like it as much are less likely to feel satisfied with the dose, and—once this is accounted for—whether shared decision-making is happening or not becomes (relatively) less important. This suggests that restrictions on which drugs are available to clients likely impacts treatment attractiveness and engagement, something which has already been explicitly stated by people with OUD.(49) Since prescribers (and programs) are currently restricted in terms of which injectable opioid agonists they can provide for iOAT, there is a corresponding limit to how many clients will be able to access the opioid agonist they would like the most. Additionally, providers who have made efforts to promote client autonomy (SDM being one avenue for doing this) have highlighted feeling constrained by system-level restrictions and regulations (e.g. policies, governing structures, etc., that establish, facilitate, and enforce how iOAT is delivered in Canada)(32) that obstruct both those efforts and the overall promotion of PCC. Given these imposed limits, it is still worthwhile for iOAT providers to focus on greater shared decision-making in daily clinical practice. Existing research has looked at dose adequacy for patients on methadone maintenance treatment, and found that “patients’ perception of participation in methadone dosage decisions” was the only variable independently associated with patients perceiving their methadone dose to be inadequate.(11) Any lack of consistent inclusion in decision-making (as reported by clients in this study) evinces a negative power dynamic between provider and client something that is known to negatively impacts clients' autonomy and health outcomes.(50–52) Likewise, some clients using illicit fentanyl may prefer fentanyl (or an analogue) as a medication option(53) or may require access to benzodiazepines—for purposes of maintenance or tapering.(54) A pilot program offering powdered (for vaporizing, injecting, and/or insufflating), and/or transdermal fentanyl (among other options) to people using criminalized opioids has demonstrated quality-of-life improvements for the participants.(55) Strict regulations and enforced surveillance (i.e. through forbidding clients to take their iOAT medication home) has also been shown to be associated with clients being discouraged from seeking medical treatment,(56) and therefore also prevents care from being patient-centered. Promotion of individual autonomy and PCC can be further constrained by medical professionals’ reactions to patients demonstrating in-depth knowledge about their own health conditions, medications, and treatments. Patients who attempt to self-advocate using relevant expertise (especially when they know more about the specific issue/treatment than a healthcare provider) encounter problems in interactions with healthcare providers, who often react to patients’ biomedically and/or experientially informed self-advocacy by reasserting control over medication and medical decisions in ways which run counter to patients’ clearly stated preferences and needs, resulting in worse outcomes.(57) Until iOAT clients are regularly included in decisions around and able to access drugs that they do “like” the effects of, achieving true dose satisfaction for a subset of iOAT clients will be as out-of-reach as those preferred drugs are. Implementation of PCC would also necessitate flexible medication provision and dose format, which includes not just take-home doses but also increased options for routes of administration such as intranasal,(58) transdermal, and inhalable.(32)
The lack of association between dose-satisfaction status and the actual dose prescribed is congruent with other literature from PCC-informed programs.(11) Research examining clients’ typical iOAT doses found that, within the spectrum of available doses, the majority of clients receive doses in the middle range with a small number (~ 5%) of individuals requiring higher or lower doses (Unpublished observations Magel et al.). These findings emphasize the importance of offering individualized flexible(8) dosing for opioid agonists. Individualized care and SDM are two fundamental aspects of PCC, which has been shown to promote client autonomy(52) increase engagement with treatment,(51) and reduce criminalized drug use, addiction severity, and psychiatric problems.(50) These are also integral parts in the building of a therapeutic relationship between provider and client, establishing a foundation in which clients are able to feel comfortable and safe opening up about their needs. This further encourages clients to be involved in the decisions around care, maximizing the potential for the provision of care that is responsive to clients’ individual needs, preferences, histories, and disabilities.(5, 32)
Current medication and dose concerns are, understandably, centered around client safety. In Canada, iOAT clients undergo a rigorous three day induction protocol, and doses are usually restricted to a maximum of 1000mg and 500mg per day (and 400mg and 200mg per session) for diacetylmorphine and hydromorphone, respectively.(23, 34) iOAT clinical trial data, comparing hydromorphone and diacetylmorphine, recorded a total of 29 (5 in hydromorphone and 24 in diacetylmorphine) serious adverse events (SAEs) among 41,027 and 44,424 recorded hydromorphone and diacetylmorphine injections, respectively.(34) All SAE’s were safely mitigated, with the most common adverse events being immediate post-injection site pruritus and somnolence (often occurring after medication change or during the titration process).(20) Out of 202 patients, 11 had an SAE opioid overdose requiring administration of naloxone, over a 6-month period.7 A case study from Tas et al. also found that diacetylmorphine injections caused respiratory regulation abnormalities for a man on long-term injectable diacetylmorphine maintenance treatment, but that even for just one subject, there was an inconsistent relationship between opioid dose and overdose risk (respiratory depression).(59) This suggests that inflexible restrictions on changes to—especially increases beyond the typical “maximum”—doses may not always provide benefits to all client’s safety, given the wide variation in tolerances and responses to opioid agonists both within and between patients. Indeed, there is documented evidence of methadone clients whose effective doses have been found to go up to over 700 mg.(9) This phenomenon is not unique to methadone—the mechanisms currently thought to account for such extreme individual variability would also be present for other opioid agonists like DAM and HDM. Most importantly, the risk of overdose for a client (in a clinical setting, who has received a known amount of a known substance), should be weighed against the risk of that client turning to criminalized opioids to supplement their OAT, and then potentially overdosing from an unknown purity substance in a non-clinical setting. This should also be considered when discussing the possibility of medication diversion, a concern often cited to justify current barriers (e.g. restrictions on take home doses) to the provision of greater flexibility and accessibility of OAT. Evidence suggests, however, that diversion has many positive effects and plays an important role in keeping people alive during the current overdose crisis driven by the toxic criminalized drug supply.(60) There is little evidence suggesting that diverted OAT medications are used by anyone other than already-regular users of criminalized opioids, or for reasons other than those individuals trying to manage their own OUD in the absence of care that is attractive, accessible, and effective for them.
While the importance and benefits of PCC are not limited to outcomes traditionally studied by medicine, the ample evidence supporting it places a responsibility on healthcare providers and stakeholders to act towards eliminating barriers to its provision. It is in the best interest of the autonomy, health, and wellbeing of clients accessing OAT to have free and informed decision-making power over how, when, where, and which medication they take, their dose(s), and whether they access their medication(s) in a supervised clinical setting or as take-home doses (or have it delivered, to maximize accessibility).
Limitations
The unique nature of this cohort poses several potential limitations, including the generalizability of findings given the uniqueness of iOAT clients and the respective use of baseline data from the SALOME clinical trial. However, given the criteria used to enroll both SALOME and RUTH participants, it is anticipated that findings from this study are reflective of individuals with opioid use disorder and thus, generalizable to this population. It is worth noting that at the time of the study, a DAM shortage took place resulting in participants temporarily switching to HDM. It is possible that, among those who switched medications, perceived dose adequacy may have acted as a proxy for “drug liking” during this time. However, this shortage is unlikely to have resulted in significant changes to findings as its duration was less than 2 months and all individuals were returned to their original medication. The inability to examine and the removal of individuals who indicated they wanted a lower dose from the analysis was a limitation in comparing groups. Still, given the dearth of individuals in this group (e.g. n = 5), removal of these individuals likely did not impact our final findings. Further, individuals receiving iOAT have autonomy to choose whether they wish to use the entire amount of their medication and are not required to use the full dose if they do not wish to.