Evaluation of Buprenorphine Extended-Release Subcutaneous Injection at Alternative Injection Locations: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Buprenorphine Extended-Release Subcutaneous Injection at Alternative Injection Locations (NCT05704543), a randomized phase 4 study. The primary outcome is Area Under the Plasma Concentration-time Curve From Study Day 1 to Day 29 (AUC0-28days) of Buprenorphine.

2. Clinical Question

The endpoint summarizes drug concentrations over time, rather than describing a clinical symptom or treatment response. The registry record presents separate geometric mean AUC values for the four groups, with a geometric coefficient of variation for each. It does not post a ratio of an alternative-site estimate to the abdominal reference estimate, a confidence interval for such a comparison, or a test of the primary objective. The arm summaries therefore allow a descriptive view of the posted exposure measurements, but do not by themselves establish whether the sites differ or whether any difference meets a prespecified criterion.

The record also lists safety outcomes, including treatment-emergent adverse events, serious adverse events, injection-site reactions, injection-site grading, and injection-site pain. These outcomes provide a separate description of events and local observations. They do not replace the primary pharmacokinetic comparison, and their detailed results are not all shown in the record.

3. Trial Design

This was a Phase 4, randomized, open-label, parallel-group study with a planned enrollment of 132 participants. Its official title describes a single-dose evaluation of relative bioavailability, safety, and tolerability in adults. The study is listed as completed. The recorded study start was 2023-03-01 and the primary completion date was 2023-11-01.

Participants were assigned to one of four injection-location groups: abdomen, back of the upper arm, buttocks, or thigh. Each group received a single subcutaneous dose of 300 mg extended-release buprenorphine on Day 1. The abdominal group served as the reference for the stated primary objective; the other three locations were test treatments. The parallel design means the registry describes separate groups assigned to different locations, rather than repeated injections at different locations in the same participant.

Randomization is recorded, but the method used to generate or implement assignments, any allocation-concealment procedures, and the allocation ratio are not reported in the registry record. Masking is listed as none, so this is an open-label study. Details about blinding of laboratory personnel or other outcome assessors are not reported in the registry record.

The primary endpoint was AUC from Day 1 to Day 29, with plasma concentrations scheduled at predose and multiple post-dose times on Day 1, followed by measurements on later study days through Day 29. The primary analysis population is identified as the Pharmacokinetic Evaluable Analysis Set. The posted arm summaries include 22.0 participants for abdomen, 17.0 for upper arm, 22.0 for buttocks, and 21.0 for thigh. The reasons these analysis counts differ from the safety denominators or from the overall enrollment are not reported in the registry record.

There are no posted inferential analyses in the registry record. The statistical model, comparison estimates, confidence intervals, hypothesis tests, and any planned interim analyses are not reported in the registry record. The tables and plots present the posted summaries; they should be read as descriptive unless an inferential result is explicitly shown.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Pharmacokinetic Evaluable Analysis Set

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Area Under the Plasma Concentration-time Curve From Study Day 1 to Day 29 (AUC0-28days) of Buprenorphine, measured over Day 1 at predose and at 1, 2, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, and 48 hours post-dose and on Days 4, 6, 8, 11, 15, 18, 22, 25, and 29.

The primary endpoint is the area under the plasma concentration-time curve from study Day 1 to Day 29, labeled AUC0-28days and measured in h*ng/mL. AUC represents overall drug exposure across the measurement period: conceptually, it summarizes concentration levels while taking account of how those levels change over time. It is used in pharmacokinetic studies because a single concentration at one time point cannot describe exposure across the full sampling window.

For this endpoint, the registry reports a geometric mean for each injection-location group and a geometric coefficient of variation as the dispersion summary. A geometric mean is a summary suited to values that are analyzed on a logarithmic scale; it is not the arithmetic average. The GCV describes variability relative to the geometric mean. It is a measure of spread, not a confidence interval and not a direct estimate of uncertainty in a comparison between locations.

The measurements began with a predose sample and scheduled post-dose samples over the first two days, followed by samples on later study days through Day 29. This repeated sampling supplies the concentration-time information used to characterize exposure over the stated interval. The registry record does not describe the calculation method for AUC, how any unscheduled or missing concentrations were handled, or the exact rules for inclusion in the Pharmacokinetic Evaluable Analysis Set.

The study objective is comparative, but the posted endpoint results are arm-level summaries. A comparative estimate, such as a relative bioavailability estimate with an uncertainty interval, is not reported in the registry record. Accordingly, the geometric means and GCVs should be read as descriptions of the reported groups, not as a complete inferential answer to the relative-bioavailability question.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record describes a randomized, open-label, parallel-group, single-dose study. In general, randomization assigns participants to study groups by chance. This can help make groups comparable on average, but it does not guarantee that every characteristic is balanced, and it does not remove the need to report the analysis. The registry does not describe how randomization was carried out, whether assignments were concealed before enrollment, or whether the groups were intended to have equal allocation.

What the endpoint summarizes

As a general statistical concept, AUC summarizes the area under a concentration-time curve. It combines concentration information across the observation window, so it reflects both the level of concentrations and how long those levels are observed. Here, the stated window is from Day 1 to Day 29, and the measurement unit is h*ng/mL. The protocol’s exact computational procedure, including handling of missing measurements, is not reported in the registry record.

The record reports geometric means rather than arithmetic means. In general, a geometric mean is calculated on a logarithmic scale and then expressed on the original scale. This is often useful for pharmacokinetic measures that vary multiplicatively or are not symmetrically distributed on their original scale. That is a general explanation, not a claim about the study’s unreported model. The statistical analysis plan and the justification for the chosen summary are not reported in the registry record.

How to read the GCV

The geometric coefficient of variation is a relative measure of dispersion around a geometric mean. It describes how variable the individual measurements are in relation to the scale of the group summary. It is not a standard error, a confidence interval, or a measure of the uncertainty in the difference between two group means. A larger GCV indicates more dispersion in that group’s reported observations, but it does not alone demonstrate a statistically meaningful difference in variability between groups.

For the posted results, the GCV accompanies each group’s geometric mean. Readers should consider the spread summary alongside the analysis count and the plotted data, where available. The registry does not report participant-level values, the distribution of AUC measurements, or a formal comparison of variability across injection locations.

Why a comparison estimate matters

The objective concerns relative bioavailability, which is a comparison of exposure between a test location and the abdominal reference. In general, a comparative pharmacokinetic analysis may report a ratio or another contrast, together with an uncertainty interval. The interval helps communicate which values remain compatible with the data under the analysis assumptions. No ratio, confidence interval, or hypothesis-test result is posted here, and the registry does not state a decision margin or acceptance criterion. Therefore, the arm-level geometric means are descriptive summaries, not a complete test of relative bioavailability.

Confidence intervals and p-values answer different questions. In general, a confidence interval conveys uncertainty about an estimated parameter, while a p-value summarizes how compatible the data are with a specified null hypothesis under a statistical model. Neither can be reconstructed from the posted summaries without additional assumptions and information. Neither is reported for this primary endpoint in the registry record.

Variation and precision

In general, over-dispersion means that observed variability is greater than a simple model would expect. When present, it can make standard errors too small if the analysis assumes less variability than the data contain. The posted GCVs show dispersion summaries, but the record does not report a model or an assessment of over-dispersion. It would therefore be inappropriate to claim that a particular variance adjustment was used or needed in this study.

The size of a group and the spread of its measurements both affect how precisely a mean or contrast can be estimated. A smaller analysis set or greater variation can limit precision. However, the registry does not provide confidence intervals for the group means or the primary comparison, so the precision of the relative-bioavailability contrast cannot be quantified from this record. Any sample-size figures elsewhere on the page are planning illustrations based on an observed effect, not observed power and not evidence that the trial was designed to achieve a particular precision.

What is documented and what is not

The registry identifies the primary analysis population as the Pharmacokinetic Evaluable Analysis Set and lists the endpoint summaries by group. It also records randomization and no masking. It does not report a statistical model, transformation details beyond the geometric-mean summary, adjustment variables, handling of missing measurements, outlier rules, confidence intervals, hypothesis tests, or interim analyses. These omissions limit what can be inferred from the posted summaries. They do not mean that a procedure was or was not used outside what is documented; the appropriate description is that it is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The study has one stated primary endpoint and several safety-related secondary outcomes. The registry lists five secondary outcome names: participants with treatment-emergent adverse events; participants with treatment-emergent adverse events identified as injection-site reactions; participants with treatment-emergent serious adverse events; injection-site grading; and injection-site pain. The record lists seven outcome measures overall, but does not describe the two other measures in the information.

Multiple endpoints or multiple location comparisons can raise a multiplicity question: if many statistical tests are performed, the chance of at least one apparently notable result can increase. In general, a prespecified testing hierarchy or adjustment can address that issue, depending on the study objective. The registry record does not report a multiplicity strategy, a testing hierarchy, or inferential results for the primary or secondary outcomes. It is therefore not possible to determine from this record whether or how multiplicity was addressed.

The primary endpoint is reported for the Pharmacokinetic Evaluable Analysis Set, but the set’s detailed inclusion criteria are not reported. The record does not explain why the primary analysis counts differ by group, how missing concentration measurements were handled, or whether any participants were excluded from analysis. It also does not report imputation methods, sensitivity analyses, or an analysis population defined by randomized assignment.

These gaps matter because missing measurements and exclusions can affect both the group summaries and the interpretation of a comparison. In general, an analysis that excludes participants with incomplete measurements can differ from one that uses all randomized participants, especially if the reasons for missingness are related to the outcome. No conclusion about the likely direction or size of such an effect can be made. The record describes the analyzed population, but its rules and missing-data methods are not reported in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry separates adverse-event reporting into a pre-injection run-in group and four post-injection groups. In the run-in period, 132 participants were at risk for serious adverse events and zero were reported; 132 were at risk for other adverse events and 26 were reported as affected. After injection, the abdomen group had zero serious adverse events among 22 participants at risk and 5 participants affected by other adverse events. The upper-arm group had zero serious adverse events among 21 at risk and 3 affected by other adverse events. The buttocks group had zero serious adverse events among 22 at risk and 4 affected by other adverse events. The thigh group had zero serious adverse events among 23 at risk and 2 affected by other adverse events. No deaths are reported in any of these groups.

These are counts, not comparative risk estimates. The groups have different denominators, and the record does not report confidence intervals or statistical comparisons for these safety counts. Zero reported serious events means none were recorded in the listed group during the reported period; it does not establish that the underlying risk is zero. The record does not provide event-level details or explain the differing safety denominators relative to the pharmacokinetic analysis counts.

The listed secondary outcomes also include injection-site reactions, grading, and pain, but detailed results for those outcomes are not present in the summarized record. The counts above should not be treated as a complete description of all local tolerability findings.

12. What the Result Does, and Does Not, Mean

The posted results establish that the registry contains group-level pharmacokinetic summaries for a randomized study of four injection locations, along with selected adverse-event counts. The primary endpoint is AUC from Day 1 to Day 29. The geometric means and GCVs provide a descriptive account of the reported exposure values and their variation within the pharmacokinetic analysis groups.

They do not, by themselves, answer the study’s comparative objective. The registry record does not post a relative bioavailability ratio, confidence interval, p-value, statistical model, or prespecified decision range. Readers therefore cannot use these summaries alone to determine the precision of a difference between a test location and the abdominal reference, or whether any such difference meets a criterion set by the study. No claim that the locations are equivalent, different, or interchangeable is supported by the posted inferential results, because such results are not reported in the registry record.

The safety counts likewise have a limited interpretation. The record reports zero serious adverse events in the listed pre-injection and post-injection groups, and it reports counts for other adverse events. Counts without comparative analyses and uncertainty estimates do not establish that an event risk is absent or that one location has a better safety profile. The registry also lists injection-site outcomes for which detailed results are not included.

General statistical interpretation depends on design and analysis details such as the randomization procedure, analysis population rules, handling of missing measurements, and the model used for the primary endpoint. Several of those details are not reported in the registry record. This is especially relevant when comparing an arm-level summary with a primary objective framed in terms of relative bioavailability: a direct contrast and its uncertainty are needed to quantify that objective.

The findings should therefore be read as posted descriptive data from a completed study, not as a full report of the trial’s statistical conclusions. The tables and plots on this page organize the reported values; they do not fill in unreported methods or comparative results.

13. Why This Trial Matters Statistically

This trial is statistically interesting because the primary question is comparative, while the posted result format is mainly descriptive. Relative bioavailability concerns exposure at each alternative injection location compared with an abdominal reference. Reporting a geometric mean for each group is informative, but a direct comparative estimate and its uncertainty are needed to show how precisely the study addresses that question.

The study also illustrates why the endpoint’s summary measure matters. AUC captures concentration over time, and geometric means and GCVs describe the center and dispersion using a scale suitable for many pharmacokinetic measurements. These summaries are not interchangeable with arithmetic means, confidence intervals, or treatment-effect tests. Understanding which quantity is shown prevents a descriptive group value from being mistaken for an inferential comparison.

Randomized assignment is an important design feature, but it does not make unreported analysis details irrelevant. The record identifies the primary population as pharmacokinetic evaluable, yet does not state the membership rules or explain the differences between the pharmacokinetic and safety denominators. A transparent account of exclusions and missing measurements would help readers assess how the analyzed groups relate to the randomized study population.

Finally, the study includes multiple locations and several safety outcomes. Without a reported analysis plan, comparison estimates, and multiplicity strategy, the displayed values should not be treated as if they were the results of a prespecified family of hypothesis tests. The statistical lesson is to distinguish the data summaries that are available from the comparative evidence needed to answer the stated objective. The record provides the former, while the latter is not reported in the registry record.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most important limitation of the posted record is that it does not include inferential results for the primary relative-bioavailability objective. There are group geometric means and GCVs, but no relative estimates, confidence intervals, p-values, or stated comparison margins. The precision and statistical interpretation of differences between locations therefore cannot be assessed from the record alone.

The statistical analysis plan is not reported in the registry record. In particular, the record does not explain the model, the calculation procedure for AUC, the handling of missing concentration measurements, the criteria for the Pharmacokinetic Evaluable Analysis Set, or any sensitivity analyses. The primary endpoint counts vary by location, and the reason for these differences is not reported. The safety denominators also differ from the primary analysis counts; the relationship between the populations is not explained.

Randomization and absence of masking are recorded, but the randomization procedure and allocation concealment are not described. The record does not state whether outcome assessment or laboratory work was masked. It also does not report a multiplicity plan for the several injection-location comparisons and listed secondary outcomes.

The safety information is limited to the available counts. Detailed results for injection-site reactions, grading, and pain are not included in the summarized record, and there are no posted comparative estimates for adverse events. The absence of reported serious adverse events in the listed groups should not be interpreted as proof of no risk.

These limitations concern what can be evaluated from the registry record. They do not establish that analyses or procedures were absent from study conduct; those details are simply not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Evaluation of Buprenorphine Extended-Release Subcutaneous Injection at Alternative Injection Locations — NCT05704543.
• Registry record last updated 2025-01-07; status last verified 2024-12.
• Results first posted 2025-01-07.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

This completed Phase 4 study enrolled 132 adults with opioid use disorder and was randomized, open-label, and parallel-group. Participants received a single subcutaneous injection of 300 mg extended-release buprenorphine in the abdomen, back of the upper arm, buttocks, or thigh. The stated primary objective was to assess relative bioavailability at alternative locations against the abdominal reference.

The primary endpoint was AUC from Day 1 to Day 29, summarized by geometric mean and GCV in the Pharmacokinetic Evaluable Analysis Set. The registry posts group summaries and adverse-event counts, including zero reported serious adverse events in the listed groups. It does not report inferential comparisons, confidence intervals, p-values, or detailed methods for the primary analysis, missing data, or multiplicity. The posted results therefore support descriptive reading, while the comparative statistical conclusion is not reported in the registry record.