This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Evaluation of Doxazosin to Alter the Abuse of Oxycodone (NCT03415581), a randomized phase 2 study. The primary outcome is Opioid Self-administration.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03415581 |
| Phase | Phase 2 |
| Condition | Opioid-use Disorder |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Double |
| Enrollment | 13 |
| Arms in the primary outcome | n/a |
| Lead sponsor | New York State Psychiatric Institute |
| Results posted | Yes |
2. Clinical Question
Population
The study description concerns adult men and women aged 21 to 59 years who abuse opioids and are physically dependent on them. Participants were to be recruited for inpatient participation; the registry record does not report the enrolled participants’ demographic characteristics or confirm how many met each eligibility characteristic.
Intervention
The intervention of interest was maintenance with doxazosin, an epinephrine receptor blocker, while participants completed testing sessions involving intranasal oxycodone. Active doxazosin was described as a daily dose of 16 mg or the highest tolerated dose; the summary also describes starting at 4 mg and increasing by 4 mg every 3 days. A cue session was included in the study procedures.
Comparator
The comparator was placebo doxazosin maintenance. The crossover design used placebo-first and active-first sequences, with the order randomized. The registry record also describes testing with active or placebo oxycodone in random order. Details about how the masking was implemented are not reported in the registry record.
Primary question
The primary question was whether mean percentage of drug choices in a laboratory self-administration task differed under doxazosin and placebo maintenance. Participants chose between drug and money, and the outcome was the mean percentage of choices for the drug. The registry record identifies the outcome but does not report its values or a treatment comparison.
3. Trial Design
This Phase 2 study, titled “Evaluation of Doxazosin to Alter the Abuse of Oxycodone,” was registered as randomized, double-masked, and crossover. It enrolled 13 participants and is listed as terminated. The study start date was 2017-02-12, and the primary completion date was 2019-12-23. The sponsor was New York State Psychiatric Institute.
The study description planned an 8-week inpatient period. During Weeks 1-2, participants were to transition from their usual opioid use to oral morphine until withdrawal dissipated, while beginning stabilization on doxazosin or placebo. The summary describes active doxazosin initiation at 4 mg, with increases of 4 mg every 3 days, toward 16 mg/day or the highest tolerated dose. The two sequences were placebo maintenance followed by active doxazosin, or active doxazosin followed by placebo, with each maintenance period described as 4 weeks.
Testing was described during Weeks 3-4 and Weeks 7-8. The summary says active or placebo oxycodone would be available in random order, with drug testing using a sample-and-choice self-administration procedure. A cue-exposure session was also described. These details describe the planned study procedures; the registry record does not report how completely they were carried out for all enrollees.
The primary outcome population was 2 participants who completed testing under both doxazosin and placebo maintenance conditions. The registry record does not explain why the outcome population was this small relative to enrollment, or provide participant flow details beyond the reported enrollment and analysis population.
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
| Stage | Placebo Doxazosin, Then Active Doxazosin | Active Doxazosin the Placebo Doxazosin |
|---|---|---|
| STARTED | 7 | 6 |
| COMPLETED | 1 | 1 |
| NOT COMPLETED | 6 | 5 |
Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed for the measure represents 2 individuals who completed testing under both doxazosin and placebo maintenance conditions.
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.
| Characteristic | Unit | Doxazosin (Placebo First) | Doxazosin (Active First) | Total |
|---|---|---|---|---|
| Participants analysed | 7 | 6 | 13 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 7 | 6 | 13 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 46.7 (SD 10.4) | 47.7 (SD 9.3) | 47.2 (SD 9.4) |
| Sex: Female, Male: Female | Participants | 1 | 0 | 1 |
| Sex: Female, Male: Male | Participants | 6 | 6 | 12 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 4 | 3 | 7 |
| Race (NIH/OMB): White | Participants | 3 | 2 | 5 |
| Race (NIH/OMB): More than one race | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 7 | 6 | 13 |
6. Primary Endpoint
The registry lists the primary outcome as Opioid Self-administration, measured over Averaged across the 8-week trial..
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Mean percentage of Drug Choices |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was opioid self-administration, expressed as mean percentage of drug choices. In the clinical laboratory task, participants chose between drug and money. The endpoint therefore describes the share of choices directed toward the drug option, averaged across the 8-week trial, as specified in the registry record.
A choice task can quantify behavior under structured conditions rather than relying only on a participant’s stated intention or retrospective report. In general, repeated choices between a drug and an alternative can be used to study drug-taking behavior under the tested conditions. This laboratory measure does not by itself establish what a participant would choose outside the study setting, and it is not a direct measure of longer-term clinical outcomes.
The registry record specifies the mean as the summary measure and standard deviation as the dispersion measure. In general, the mean describes the average outcome, while the standard deviation describes variability among observations. The record identifies 2 participants as having completed testing under both maintenance conditions, but does not report the condition-specific means, standard deviations, treatment contrast, confidence interval, or test result. Consequently, the endpoint definition is available, but the magnitude and precision of the observed comparison are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary endpoint and its measurement, but it does not post numerical outcome values. There is no reported mean percentage of drug choices under either maintenance condition, no reported difference between conditions, and no confidence interval or p-value. The direction, magnitude, and statistical precision of the primary comparison therefore cannot be described from the registry record.
The number analyzed for the primary outcome is especially important for interpretation: the record says 2 participants completed testing under both doxazosin and placebo maintenance conditions. This is the stated analysis population for the measure, not the total enrollment of 13. A small analysis population limits how much can be learned about the range of responses among participants and makes estimates sensitive to the observations from those who completed both conditions. Because the outcome values are not posted, the size of that sensitivity cannot be assessed.
The crossover structure means that the intended comparison was within participants across maintenance conditions, rather than a simple comparison of unrelated groups. In general, this can reduce the influence of stable differences between people because each participant contributes information under both conditions. It also makes period effects, treatment order, and changes over time relevant considerations. The registry record does not report analyses of these factors, nor does it describe whether any carryover assessment was undertaken.
The registry lists opioid craving as a secondary outcome, but its results are not reported in the registry record. It also records the trial status as terminated. The reason for termination and its timing relative to recruitment, testing, or analysis are not reported in the registry record, so the status alone cannot explain the small primary analysis population.
The adverse-event record lists no serious adverse events and no deaths in either maintenance group, alongside other adverse events. These safety counts are descriptive; they do not replace the missing primary outcome estimates and should not be interpreted as a comparison of efficacy. No conclusion about the primary treatment comparison is supported by the posted numerical data because those outcome results are absent.
9. Statistical Methods Explained
The registry describes a randomized, double-masked crossover design. General explanation: randomization assigns treatment order using a chance-based procedure, helping reduce systematic differences in assignment. Double masking generally means that more than one party involved in the study is kept unaware of treatment assignment. The registry record does not specify which parties were masked or how masking was maintained.
What does crossover mean?
In a crossover study, participants receive or are assessed under more than one condition, and each person can contribute observations to each condition. Here, the record describes placebo-first and active-first doxazosin maintenance sequences, with testing under both maintenance conditions for the primary outcome population. This design makes paired comparisons possible: a participant’s outcome under one condition can be compared with that same participant’s outcome under the other condition.
General explanation: pairing can account for stable characteristics that differ between participants, since the comparison is within the same person. It does not automatically eliminate all sources of bias or uncertainty. Outcomes can change with time, and a prior treatment period can potentially influence later measurements. The registry record does not report a washout plan, a carryover analysis, a period-effect analysis, or details of how the sequence was included in the primary analysis. Those elements should not be assumed.
What does the endpoint summary describe?
The primary outcome is continuous and is summarized as a mean, with standard deviation identified as the measure of dispersion. General explanation: the mean gives a central summary of observed values, while the standard deviation describes how spread out those values are around the mean. A standard deviation is not the same as a confidence interval. The former describes observed variability; the latter expresses uncertainty around an estimated quantity under a statistical model.
The outcome is mean percentage of drug choices in a laboratory choice task, averaged across the 8-week trial. The registry record states that 2 participants completed testing under both doxazosin and placebo maintenance conditions. However, the posted record does not give the actual means or standard deviations, the paired treatment contrast, or its uncertainty. It is therefore not possible to evaluate the observed size or precision of the contrast from the registered results.
How should a confidence interval be understood?
General explanation: a confidence interval presents a range of values compatible with the observed data and the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, while neither width nor location alone establishes whether a result is clinically important. Interpretation depends on the outcome scale, the comparison being estimated, and the study context. No confidence interval for the primary outcome is reported in the registry record.
What can a p-value establish?
General explanation: a p-value measures how unusual data at least as discrepant as those observed would be under a specified statistical model and null hypothesis. It is not the probability that the null hypothesis is true, nor does it express the size or practical importance of an effect. A p-value must be read alongside an estimate and its uncertainty. No primary-outcome p-value or inferential analysis is reported in the registry record.
Why does the analysis population matter?
The registry distinguishes enrollment from the population analyzed for the primary measure. The 13 enrolled participants and the 2 participants who completed testing under both conditions describe different stages or populations. General explanation: incomplete outcome data can reduce precision and may create bias if the likelihood of having complete data is related to outcomes or treatment experience. To assess this, readers need participant flow, reasons for missing measurements, and the analysis approach. Those details are not reported in the registry record.
The record includes planning assumptions describing illustrations based on fractions of the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It says these are planning illustrations rather than the trial’s own design justification. The numeric outputs are not reported in the registry record. Such illustrations are not observed power and cannot substitute for reported outcome estimates or their uncertainty.
Over-dispersion is a general issue when observed variability is greater than a model assumes. In that situation, model-based uncertainty can be understated if the analysis does not account for the extra variability. The endpoint is described as continuous and summarized by a mean and standard deviation; the registry record does not report a model or any assessment of over-dispersion. No specific distributional assumption or method should therefore be attributed to the trial.
10. Multiplicity, Missing Data and Analysis Populations
The registry record identifies opioid self-administration as the primary outcome and opioid craving as a secondary outcome. It reports 2 outcome measures, but does not provide the results for either outcome. The number of analyses is recorded as 0. A prespecified hierarchy, multiplicity adjustment, or other strategy for controlling the chance of false-positive findings across outcomes is not reported in the registry record.
General explanation: when a study evaluates multiple outcomes or multiple contrasts, the chance of at least one apparently notable result can increase if each is interpreted independently. Statistical plans can address this through prespecified primary outcomes, ordered testing, or adjustment procedures. Without a reported plan and results, it is not possible to determine whether multiplicity was considered or how it would affect interpretation.
The stated primary-outcome population comprises 2 participants who completed testing under both maintenance conditions, compared with enrollment of 13. The reasons that other enrollees do not appear in the primary outcome population, the timing and amount of missing data, and the handling of incomplete records are not reported in the registry record. No intention-to-treat, per-protocol, or other named analysis population is described.
General explanation: missing observations can affect both precision and validity. A complete-case analysis may be less representative if completion is related to treatment, outcome, or participant characteristics. Sensitivity analyses can examine how conclusions might change under different assumptions about missing outcomes. The registry record does not report such analyses or the assumptions used to handle missing data.
Although the record identifies crossover order and a paired outcome population, it does not describe the primary statistical model or whether it accounted for period, sequence, or carryover. Those analysis details are not reported in the registry record, so no adjustment strategy can be inferred.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Placebo Maintenance | 0 | 13 | 0.0% |
| Doxazosin Maintenance | 0 | 13 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Placebo Maintenance | 0 of 13 |
| Doxazosin Maintenance | 0 of 13 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo Maintenance | 2 of 13 |
| Doxazosin Maintenance | 5 of 13 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo Maintenance | Doxazosin Maintenance |
|---|---|---|---|
| Orthostasis | Cardiac disorders | 2 of 13 | 5 of 13 |
| Bradychardia | Cardiac disorders | 0 of 13 | 1 of 13 |
| Chest Pain | General disorders | 0 of 13 | 1 of 13 |
The registry lists 13 participants at risk in each maintenance group. It records 0 serious adverse events in the placebo maintenance group and 0 in the doxazosin maintenance group. Deaths are recorded as 0 in each group. For other adverse events, the record lists 2 affected in the placebo maintenance group and 5 affected in the doxazosin maintenance group.
These are descriptive counts. The record does not provide event terms, severity details beyond the serious-versus-other classification, timing, or an analysis comparing groups. It also does not explain whether the counts refer to unique participants across the crossover periods or how repeat events were handled. Because participants could experience both maintenance conditions, the group counts should not be added to infer a number of distinct people.
Zero recorded serious adverse events and deaths in these registry entries should be read as the posted counts, not as proof that an event could not occur or as evidence of comparative safety. The limited primary outcome population and the absence of detailed event information constrain interpretation. The registry record does not report further safety analyses.
12. What the Result Does, and Does Not, Mean
The record establishes that a randomized, double-masked crossover study of doxazosin and oxycodone-related laboratory outcomes was conducted and terminated, with enrollment of 13. It identifies mean percentage of drug choices as the primary endpoint and states that 2 participants completed testing under both doxazosin and placebo maintenance conditions. These registry entries describe the study and the available primary analysis population.
The record does not report numerical primary outcome results. It therefore does not establish whether drug-choice behavior was higher, lower, or similar under either maintenance condition, nor how large or precise any comparison might be. No treatment-effect estimate, confidence interval, or p-value is posted. The endpoint definition cannot be treated as evidence of a particular result.
General explanation: a laboratory choice outcome can inform understanding of behavior in the structured conditions in which it was measured. It does not on its own establish effects on clinical outcomes or behavior outside those conditions. The study description includes opioid craving as a secondary outcome, but no result for that outcome is reported in the registry record.
The crossover design offers a within-participant comparison in principle, but interpretation also depends on completion, sequence, time effects, and the analysis used. The record does not provide enough analysis detail to assess these issues. The primary analysis population of 2 also means that any estimate, if reported, would need to be interpreted with attention to its precision and the narrow set of participants contributing complete paired testing.
The posted safety counts describe recorded events in the maintenance groups. They do not answer the primary efficacy question, and the available detail is insufficient for a full comparative safety assessment. Overall, the registry record documents the trial structure and selected counts, but not enough outcome information to support a conclusion about the primary comparison.
13. Why This Trial Matters Statistically
This study is statistically notable because its crossover design makes a within-participant comparison central to the intended question. In general, such a design can make efficient use of participant observations by comparing each person under different conditions. Its interpretation depends on having complete measurements under both conditions and on accounting appropriately for treatment order and changes across periods.
The registry reports that 13 participants enrolled, while the primary outcome population comprised 2 participants who completed testing under both doxazosin and placebo maintenance conditions. This distinction matters: enrollment is not the same as the number contributing to a paired treatment comparison. The registry record does not explain the difference or describe participant flow, which limits assessment of completion and potential selection effects.
Also important is the separation between a clearly defined endpoint and a reported result. Mean percentage of drug choices is specified, along with its general measurement context, but no numerical condition-specific values or contrast are reported. Without an estimate and a measure of uncertainty, statistical interpretation cannot move from the question the study posed to an answer about the observed data.
The record’s status as terminated, the small primary analysis population, and the absence of outcome estimates make transparent reporting especially consequential. A complete account of analysis methods, missing outcomes, and results would help readers distinguish design intent from evidence actually available for evaluation. The available record supports discussion of these statistical issues without supporting a conclusion about the treatment comparison.
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.
Several trial-specific limitations follow from what the registry record reports and does not report. First, the primary outcome population was 2 participants, despite enrollment of 13. The record does not explain why only those participants completed testing under both maintenance conditions. Without participant flow or reasons for noncompletion, the possible effect of missing outcome data cannot be assessed.
Second, no numerical primary outcome results are reported. Condition-specific means, standard deviations, a paired contrast, confidence interval, and p-value are not available in the registry record. The primary comparison therefore cannot be evaluated for direction, magnitude, or precision. Results for opioid craving, the listed secondary outcome, are also not reported in the registry record.
Third, although the design is identified as randomized, double-masked, and crossover, the record does not report the statistical model, handling of treatment sequence or period, assessment of carryover, or details of the masking procedure. The protocol’s sample-size justification, interim analyses, and detailed statistical analysis plan are not reported in the registry record. The planning assumptions describe illustrations, not the trial’s own design rationale, and their numeric outputs are not reported.
Finally, the trial is listed as terminated, but the reason and timing are not reported in the registry record. The safety entries give counts but not event terms or fuller event-level detail. These omissions limit interpretation of both the primary outcome and the safety profile; they should not be filled by assumptions about why the trial ended or how the analyses were conducted.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of Doxazosin to Alter the Abuse of Oxycodone — NCT03415581.
- Registry record last updated 2021-04-12; status last verified 2021-03.
- Results first posted 2021-04-12.
- 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.
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18. Record Summary
The registry record describes a Phase 2 randomized, double-masked crossover study of doxazosin and oxycodone abuse-related outcomes. It lists 13 participants enrolled, a terminated status, and primary completion on 2019-12-23. The sponsor was New York State Psychiatric Institute.
The primary endpoint was mean percentage of drug choices in a laboratory self-administration task, averaged across the 8-week trial. The stated primary outcome population was 2 participants who completed testing under both doxazosin and placebo maintenance conditions. No numeric primary outcome results or secondary opioid-craving results are reported in the registry record.
The safety entries report 0 serious adverse events and 0 deaths in each maintenance group, with other adverse events recorded for 2 in placebo maintenance and 5 in doxazosin maintenance. Details of the analysis plan, missing-data handling, and reason for termination are not reported in the registry record.