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 Impact of Buspirone Maintenance on the Reinforcing Effects of Cocaine (NCT01639157), a randomized na study. The primary outcome is Number of Times Cocaine Was Selected in the Presence of a Monetary Reward Alternative.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01639157 |
| Phase | NA |
| Condition | Cocaine Use Disorders |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Triple |
| Enrollment | 9 |
| Arms in the primary outcome | n/a |
| Lead sponsor | William Stoops |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned people with cocaine use disorders. Registry enrollment was 9. The primary outcome description places testing during a 2 week inpatient admission; further eligibility details are not reported in the registry record.
Intervention
During buspirone maintenance, subjects received 30 mg buspirone daily. The study investigated whether this maintenance condition changed the reinforcing effects of cocaine and alternative reinforcers.
Comparator
The comparator was placebo maintenance, described as 0 mg buspirone daily. The randomized crossover design means the comparison concerns maintenance conditions within the study design, but the order, timing, and transition procedures are not reported in the registry record.
Primary question
The primary measure was the number of times cocaine was selected when a monetary reward was available as an alternative. The research question was whether cocaine selection differed across buspirone and placebo maintenance at the available cocaine dose levels. The registry record does not report a single analyzed comparison or result that answers this question.
3. Trial Design
This was a randomized, triple-masked, crossover study of buspirone versus placebo maintenance. The registry lists the study as completed and reports enrollment of 9. The condition was cocaine use disorders; the study was described as a human laboratory investigation of cocaine's reinforcing, subjective, and performance effects during maintenance on buspirone or placebo.
The buspirone condition was 30 mg daily, and the placebo condition was described as 0 mg buspirone daily. In the primary outcome description, participants completed testing for each cocaine dose level during both maintenance conditions. Testing was described as one test per cocaine dose level per intervention for each participant during a 2 week inpatient admission. The registry does not describe the dose levels, sequence of conditions, length of maintenance before testing, or any washout procedure.
Randomization concerns how treatment conditions are assigned; masking concerns awareness of the assigned condition. The record identifies the study as randomized and triple-masked but does not specify which parties were masked or how randomization and masking were implemented. A crossover design can allow comparisons across conditions within the same participant, but interpretation depends on the actual sequence, timing, and analysis. Those details are not reported in the registry record.
The study began in 2012-09, reached primary completion in 2014-12, and is listed as completed. Its brief summary characterizes the work as preliminary research intended to inform further investigation of buspirone as a pharmacotherapy for cocaine use disorders. The record does not report a sample-size justification or a detailed protocol for the inpatient testing.
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 | Buspirone Then Placebo | Placebo Then Buspirone |
|---|---|---|
| STARTED | 4 | 5 |
| COMPLETED | 4 | 5 |
| NOT COMPLETED | 0 | 0 |
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 | All Study Participants |
|---|---|---|
| Participants analysed | 9 | |
| Age, Continuous | years | 39.4 (26 to 48) |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 7 |
| Region of Enrollment: United States | participants | 9 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Times Cocaine Was Selected in the Presence of a Monetary Reward Alternative, measured over One test per cocaine dose level per intervention for each participant over his/her 2 week inpatient admission.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | Number of Cocaine Choices |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was the number of times cocaine was selected when a monetary reward alternative was available. The registry describes the measure as a mean, with standard error as its dispersion measure. It says the reinforcing effects of cocaine were assessed with a modified progressive ratio procedure: subjects made 6 choices between an available cocaine dose and money worth US$0.25. The measure was collected for each cocaine dose during both buspirone and placebo maintenance.
This endpoint operationalizes reinforcement as choice behavior under a defined alternative. Counting cocaine selections captures how often cocaine was chosen in this task, rather than relying only on a participant's subjective rating. The monetary alternative provides a competing option, making the measure relevant to the study's stated interest in cocaine and alternative reinforcers.
The registry describes testing across dose levels and maintenance conditions rather than a single standalone endpoint value. It does not supply the dose-specific means, standard errors, or a single comparison result in the primary outcome record. Accordingly, the endpoint definition explains what the study intended to measure, but it does not establish how cocaine choice differed between maintenance conditions.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies an important distinction between a defined outcome and a reported treatment-effect estimate. The primary measure is clearly described: cocaine selection counts in a choice procedure with money as an alternative, collected across cocaine dose levels under buspirone and placebo maintenance. But the registry does not reduce those dose- and condition-specific measurements to one comparison. Its outcome status indicates that the primary outcome has several categories or time points and was not reduced to a single comparison. The analyses count is 0.
As a result, the record does not provide an estimated difference between buspirone and placebo, uncertainty around such a difference, or a statistical test of the primary question. It is not possible to infer the direction, magnitude, or precision of a treatment contrast from the endpoint description alone. The study hypothesis in the brief summary—that buspirone would attenuate cocaine reinforcement and increase reinforcement from alternatives—is a stated hypothesis, not a reported finding.
The crossover design may permit within-participant comparisons, but the record does not report the condition sequence, dose-specific results, or analytic method needed to interpret such comparisons. It would be inappropriate to treat the enrollment count as a result or to infer a treatment effect from the design description. Likewise, the registry's listing of secondary outcomes does not establish that any of them changed across conditions; their results are not reported in the record.
These omissions matter for precision as well as direction. Without estimates and their uncertainty, a reader cannot judge whether the data are compatible with a range of possible effects or distinguish a small estimated contrast from a large one. The record also does not report a prespecified primary contrast, a statistical analysis plan, or whether any outcome-specific adjustments were made. These details should not be assumed from the presence of a randomized, masked design.
The posted safety counts are descriptive: each listed condition has 9 at risk and 0 serious adverse events and 0 other adverse events. These counts do not answer the primary reinforcement question and do not provide a comparison of cocaine choice. Deaths are not reported in the registry record. The adverse-event data should therefore be read separately from the unreported efficacy analysis.
Overall, the registry supports a description of the laboratory question, intervention conditions, and outcome measurement. It does not support a numerical conclusion about whether cocaine selection differed during buspirone versus placebo maintenance. The study's preliminary rationale should not be mistaken for evidence that its hypothesized effects were observed.
9. Statistical Methods Explained
Several statistical ideas help distinguish what this record describes from what it establishes. The following are general explanations, applied only to the study details recorded in the registry.
What does randomization contribute?
In general, randomization assigns study conditions through a chance-based procedure rather than participant or investigator choice. It can reduce systematic differences in condition assignment, but it does not itself guarantee that groups or periods are comparable in every respect. The registry identifies the study as randomized, but does not report the sequence-generation method, allocation concealment, or how condition order was assigned.
How does a crossover design affect interpretation?
In general, a crossover design exposes participants to more than one condition and can support comparisons within the same participant. Such comparisons may account for stable characteristics that differ between people. They also require attention to period effects, order effects, and carryover from an earlier condition. The record identifies a crossover model and says testing occurred under both maintenance conditions. It does not report the condition sequence, washout arrangements, or how period and carryover effects were handled. Those features cannot be inferred from the design label alone.
What does masking mean?
In general, masking is intended to limit the influence of knowledge about assigned treatment on behavior, assessment, or analysis. The record labels this study triple-masked, but does not identify the masked parties or describe how masking was maintained. The label is useful design information; it does not replace details about implementation or assessment of masking.
What does the primary measure capture?
The registry defines a continuous measure summarized as a mean, with standard error as the stated dispersion. The underlying outcome is a count of cocaine selections in a choice task. The task involved 6 choices between a cocaine dose and money worth US$0.25, with tests at each dose level during each maintenance condition. In general, a mean describes the average measured outcome, while a standard error describes the uncertainty associated with an estimated mean. Neither statistic can be interpreted for this trial without the reported values and a clear account of which dose, condition, and comparison each value represents.
The count is bounded by the choices available in the task, and repeated dose-level observations from the same participant are likely related by design. In general, analysis of repeated observations should account for their dependence rather than treating every observation as independent. The registry does not report the model used, the handling of within-participant correlation, or whether dose levels were analyzed separately or together. It also does not report the distribution of observed counts. It is therefore not possible to assess whether a particular analytic approach was suitable.
Why do estimates and confidence intervals matter?
In general, an effect estimate describes the size and direction of a comparison. A confidence interval communicates the uncertainty around that estimate and the range of values reasonably compatible with the data under the model. A significance test addresses a related question but cannot substitute for the estimate and its precision. The registry record does not report a primary comparison estimate, confidence interval, or test result, so none can be interpreted for the primary question.
What is over-dispersion, and is it relevant?
In general, count outcomes can vary more than a simple statistical model assumes. This is called over-dispersion; if ignored, uncertainty estimates may be too small. Whether over-dispersion is relevant depends on the observed distribution and the chosen analysis. The registry does not report the outcome distribution or an analysis model, so it is not possible to determine whether over-dispersion occurred or how it was addressed. This is a general consideration for count outcomes, not a finding about this study.
How should planning calculations be read?
In general, sample-size calculations describe planning assumptions, not observed treatment effects or evidence that a study had a particular probability of detecting a true effect. The stated planning approach uses a two-sided significance level of 0.05, equal allocation between conditions, and a normal approximation; its target effect is expressed as a fraction of the observed effect. Such figures are illustrations based on those assumptions, not the trial's own design justification. The registry does not report a sample-size justification, and planning illustrations should not be described as observed power.
The distinction between an analysis and a planning calculation is important. A planning calculation cannot supply the missing dose-specific outcome values, treatment contrast, or uncertainty. It can only show the implications of its assumptions. Since the registry does not report the primary analysis, those planning assumptions do not resolve the clinical or statistical question posed by the trial.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is described across multiple cocaine dose levels and both maintenance conditions. The registry explicitly indicates that the outcome has several categories or time points and was not reduced to a single comparison. This creates an interpretive issue: a result for one dose or time point would not automatically represent the overall treatment contrast, and multiple comparisons can complicate interpretation. The record does not report a prespecified contrast, a multiplicity adjustment, or an analysis plan specifying how dose-level results were to be combined or interpreted.
The registry lists 27 outcome measures and 0 analyses. The listed secondary outcomes include peak ratings on adjective and visual analog scales, including stimulant, sedative, euphoric, good-effect, bad-effect, and active/alert/energetic ratings, as well as peak systolic blood pressure. Listing an outcome does not establish that results were analyzed or that an observed change occurred. The registry record does not report those results or explain how multiplicity across outcomes was addressed.
Missing-data handling and analysis populations are also not reported in the registry record. The record does not say whether all randomized participants contributed to every endpoint, how incomplete testing was handled, or whether the analysis followed an intention-to-treat or another population definition. These omissions matter in a crossover study because incomplete observations can affect which condition comparisons are available. No imputation approach, exclusion criteria for analysis, or sensitivity analysis is reported.
Without those details, readers cannot evaluate the robustness of any treatment estimate or determine whether the analyses followed a prespecified plan. Because no primary analysis result is reported, these are limits on interpretation rather than evidence of a particular analytic error.
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 |
|---|---|---|---|
| Buspirone | 0 | 9 | 0.0% |
| Placebo | 0 | 9 | 0.0% |
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 |
|---|---|
| Buspirone | 0 of 9 |
| Placebo | 0 of 9 |
The registry reports adverse-event counts separately for buspirone and placebo. For each condition, 9 were listed as at risk; serious adverse events were 0 and other adverse events were 0. These are reported counts for the recorded conditions, not estimates of the probability of an event or a formal comparison between conditions.
The study is a crossover, and the registry lists at-risk counts under both conditions. Those condition-level counts should not be added or interpreted as a count of distinct participants. The record does not explain the event-collection window, definitions used for other adverse events, or whether every event category was actively assessed in the same way across conditions.
Deaths are not reported in the registry record. A zero count for reported serious or other adverse events means no events are recorded in those categories in this entry; it does not establish that an event was impossible or that the conditions have equivalent safety. The small enrollment and absence of reported analysis results also limit what can be inferred from these descriptive counts. These figures should be read as registry reporting, not as a comprehensive comparative safety assessment.
12. What the Result Does, and Does Not, Mean
The record establishes the study's central laboratory question and how it was intended to be measured. Participants with cocaine use disorders were studied during buspirone maintenance at 30 mg daily and placebo maintenance described as 0 mg buspirone daily. The primary measure counted selections of cocaine when money was offered as an alternative, across cocaine dose levels. The study was randomized, triple-masked, and crossover, and its registry status is completed.
What the record does not establish is the primary treatment effect. It does not report dose-specific outcome values or a single analyzed contrast between maintenance conditions. The stated hypothesis that buspirone would attenuate cocaine's reinforcing effects and increase reinforcement from alternatives is not a result. Without an estimate and its uncertainty, no conclusion about the direction, size, or precision of a difference in cocaine choice can be drawn from the registry entry.
The record also does not establish a clinical treatment benefit. The endpoint is a choice measure from a human laboratory procedure, not a reported measure of longer-term cocaine use or treatment outcome. The brief summary describes the study as preliminary and as intended to support further research. That purpose should not be confused with proof of efficacy, nor does the absence of reported outcome analyses establish that the intervention has no effect.
Likewise, the adverse-event counts are limited registry data. The record lists no serious or other adverse events in either condition, but does not report deaths or a detailed safety analysis. Those counts cannot establish that the conditions have equal safety or rule out uncommon events.
The most defensible reading is therefore narrow: this record documents a randomized crossover laboratory study, its maintenance conditions, and its intended behavioral endpoint, but does not report the statistical results required to answer the primary comparison. Further interpretation would require outcome estimates, uncertainty measures, and analytic details that are not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically interesting because its endpoint connects a behavioral choice task with a question about reinforcement. Rather than measuring only subjective experience, it records how often cocaine is selected when money is also available. The registry's description makes the measurement process and the competing alternative explicit, which helps define what the outcome represents.
The crossover design is also relevant. In general, observing participants under more than one condition can make within-participant comparisons informative, because stable differences between participants need not drive the contrast. But crossover studies require clear reporting of condition sequence, timing, and possible carryover. Those details are not reported in the registry record, and the design label alone cannot establish that these issues were addressed.
The primary outcome is collected at multiple cocaine dose levels. That makes it important to distinguish dose-specific patterns from a single overall comparison, and to understand how repeated observations are analyzed. The registry itself flags that the outcome was not reduced to one comparison. This is not a minor reporting detail: without a defined contrast and estimates, a reader cannot tell whether the central hypothesis was supported, what size of difference was observed, or how uncertain it was.
The study is described as preliminary research, and its record illustrates why design descriptions and results must be read separately. A carefully described research question does not substitute for reported estimates, and a hypothesis does not establish a finding. The registry's value is in documenting the planned laboratory comparison and its outcome definition; its statistical limitation is that it does not report an analysis that answers that 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 limitations specific to this trial follow from the registry entry. Enrollment was 9, and no primary analysis result is reported. Without dose-specific values, an estimated contrast, or an uncertainty interval, the magnitude and precision of any difference in cocaine selection cannot be assessed. The record's completed status does not itself supply those missing results.
The outcome was measured at multiple cocaine dose levels under both maintenance conditions, but the registry does not identify a single primary contrast or explain how dose levels were handled analytically. It does not report the condition sequence, timing of testing relative to maintenance, or washout procedures. These missing crossover details prevent assessment of potential period, order, or carryover effects.
The record identifies randomization and triple masking but does not describe their implementation, identify the masked parties, or report whether masking was assessed. It does not give detailed eligibility criteria, participant characteristics, or information about the analysis population. Missing-data procedures, exclusions, and sensitivity analyses are also not reported in the registry record.
Although 27 outcome measures are listed, the analysis count is 0. The entry does not report whether multiplicity was addressed, which outcomes were prespecified, or how secondary outcomes were analyzed. The registry also does not report a sample-size justification. Planning illustrations based on an observed effect are not a substitute for the trial's design rationale or for observed results.
Finally, the safety information is limited to recorded event counts, with deaths not reported in the registry record. The study's human-laboratory choice measure is not a reported long-term clinical outcome. Together, these limitations restrict conclusions to the documented design and endpoint definition; they do not establish either benefit or lack of benefit.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Impact of Buspirone Maintenance on the Reinforcing Effects of Cocaine — NCT01639157.
- Registry record last updated 2016-02-19; status last verified 2016-01.
- Results first posted 2016-02-19.
- 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
NCT01639157 is a completed, randomized, triple-masked crossover study titled “Impact of Buspirone Maintenance on the Reinforcing Effects of Cocaine.” The registry reports enrollment of 9 and lists cocaine use disorders as the condition. The study compared buspirone maintenance at 30 mg daily with placebo maintenance described as 0 mg buspirone daily.
The primary outcome was the number of times cocaine was selected when money was available as an alternative, measured across cocaine dose levels during a 2 week inpatient admission. The registry describes a modified progressive ratio choice procedure involving 6 choices between cocaine and US$0.25. It does not report a single primary comparison or analysis result; the analysis count is 0.
The record lists 27 outcome measures and reports 0 serious adverse events and 0 other adverse events under each condition, with 9 at risk in each. Deaths are not reported in the registry record. The stated rationale is preliminary investigation to inform further research, not a reported conclusion about treatment efficacy.