The study has several limitations. Due to the retrospective nature of the study, there were no control groups and the results are only descriptive. However, the patient data were used to assess any general trends associated with the switch to Suboxone, which may provide an insight into the best clinical practices for using Suboxone as a replacement for Subutex. Also the number of the patents is relatively low but represents more than 30% of all buprenorphine treated patients in Finland at the study time and nearly all of the patients at the 5 centers. A survival analysis of the client characteristics and history regarding the time to drop out could have been interesting. Given the relatively small sample size and the scope of this study, however, this sample may not have sufficient power to detect any but the strongest patterns. Satisfaction and compliance differed significantly amongst the treatment centers, thus site specific issues might account for findings also.
The main aim of this study was to follow the medication dose and adverse events during a transfer from buprenorphine to buprenorphine-naloxone combination. The possible dose adjustments were decided by the doctors and were based on each individual's weaning, withdrawal symptoms and adverse events.
During the first four weeks, 50% of the patients reported adverse events. However, only one patient discontinued Suboxone due to adverse events or dissatisfaction, and one patient left the treatment program (retention rate of 98.5%). This indicates that the side effects at this point probably might not predict patients' likelihood of staying in treatment. Indeed, patient records indicate that many of the reported adverse events were interpreted as being the result of anxiety about being forced to switch to Suboxone. However, it is notable that during 4 month follow up period only 43.3% of the patients continued with Suboxone and 16 (61.5%) of these 26 patients also reported adverse events. It should be noted anxiety interpretation is more of a speculation than measured assessment.
Interestingly, over half of the patients still on Suboxone during the 4 month follow up asked for a dose reduction of Suboxone. This may indicate that the adverse events could be related to higher buprenorphine serum levels, because buprenorphine in Suboxone has slightly higher sublingual bioavailability than the buprenorphine in Subutex . The dose reductions of Suboxone were mainly done during the follow-up period which may indicate that bioavailability of high dose of Suboxone in the long term should be more thoroughly investigated. It should be noted, however, that the earlier Australian study  had found a need for a dose increase, rather than a decrease, when switching from buprenorphine to the combination medication, that could be related to the "low" (12 mg) average dose of Suboxone in that study.
During the follow-up period relative high number of patients (56.7%) discontinued with Suboxone. Most of them were either transferred to methadone (21.7%), back to Subutex (15%), discontinued (11.7%) the treatment or moved to other treatment centers (8.3%, no records). The most common reason for methadone transfer generally in Finland is polydrug abuse. However, in this study misuse of buprenorphine and/or lack of compliance accounted almost half of the discontinuations during the follow-up period. It is possible that psychiatric distress, when patients did not feel confident with the forced transfer from Subutex to Suboxone, may lead to "illegally top-up" with Subutex, that in turn could lead to medication change to methadone. It is possible also, that because the high illicit use of buprenorphine in Finland , the treating personnel had a mistrust on patients reports of Suboxone adverse events, and instead of chancing back to Subutex patients were changed to methadone. Thus, the "forced" transfer event could be a unique situation in Finland and may not be present elsewhere i.e. in USA and Canada, where Suboxone is the main medication.
Switching from Subutex to Suboxone did not increase abuse of other opioids. Based on the retrospective nature and small numbers in the study, no solid conclusions about Suboxone diversion can be done. However, interestingly during the follow-up period of the 60 opioid dependent patients, only 5 patients attempted to misuse Suboxone. Furthermore, they reported that while they tried to inject Suboxone, they would not repeat the experience, suggesting that the transfer to Suboxone may also serve as part of an overall strategy to curb misuse of buprenorphine.
In conclusion, a transfer from Subutex to Suboxone should be carefully discussed and planned in advance with the patients and after the transfer adverse events should be regularly monitored. With regard to buprenorphine abuse, the combination product seems to have a more favorable safety profile than treatment with buprenorphine alone. The results of this study suggest that in high dose Suboxone treatment, dose adjustments should be considered, especially in the later phase of the treatment, if patients report an unusually high number of adverse events. Also based on the clinical data gathered it is recommended that transfers should be discussed and planned in advance with the patients to minimize psychiatric distress and lack of compliance leading to lower retention rates.