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 Reinforcing Effects of Cocaine During Phendimetrazine Maintenance (NCT02522325), a randomized phase 1 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 | NCT02522325 |
| Phase | Phase 1 |
| Condition | Cocaine Use Disorder |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Triple |
| Enrollment | 30 |
| 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 Disorder in an inpatient human laboratory study. The registry lists enrollment of 30, but does not report how many participants contributed data to the primary outcome or how the analysis population was defined.
Intervention
Participants were to receive oral phendimetrazine maintenance, administered twice daily for approximately two weeks, at a target dose up to 210 mg/day. The outcome description places cocaine-choice testing after at least seven days of maintenance at the target dose.
Comparator
The comparator was oral placebo maintenance, also described as twice daily for approximately two weeks. Cocaine-choice testing was described during placebo maintenance as well as phendimetrazine maintenance. The record does not report the sequence of these conditions or how much time separated them.
Primary question
The primary question was how often cocaine was selected when participants could instead choose a monetary reward. The modified progressive ratio procedure involved 10 choices between a portion of each available cocaine dose and US$0.25. The outcome was intended to characterize cocaine’s reinforcing effects across maintenance conditions. The registry record does not report the observed choice results, so it does not establish the direction or size of any difference between conditions.
3. Trial Design
This was a Phase 1, randomized, triple-masked, crossover study. Its title is “Reinforcing Effects of Cocaine During Phendimetrazine Maintenance,” and its official title identifies it as an inpatient behavioral-effects study. The registry lists Cocaine Use Disorder as the condition and describes the setting as an inpatient human laboratory study. Enrollment was 30. The record lists a start of 2015-08, primary completion in 2018-12, and status as completed.
A crossover design generally compares more than one condition within participants, rather than assigning each participant to only one condition for the entire study. This can help distinguish condition-related changes from stable differences between participants. The registry identifies the model as crossover, but does not report the condition sequence, randomization procedure, washout interval, or the number of participants who completed each condition. The trial is also listed as randomized and triple-masked; who was masked and how masking was maintained are not reported in the registry record.
The maintenance descriptions specify oral placebo or oral phendimetrazine administered twice daily for approximately two weeks. The phendimetrazine description gives a maximum target of 210 mg/day. The primary outcome timeframe refers to testing after at least seven days of placebo maintenance or maintenance at the target phendimetrazine dose. Both arm descriptions mention acute cocaine and placebo administration during placebo maintenance. In particular, the phendimetrazine arm description also uses the phrase “during placebo maintenance” for acute administrations. That wording does not clearly explain the acute-testing sequence under phendimetrazine maintenance.
The registry’s planned measurement concerns behavioral choices, not a reported clinical outcome. The record does not provide a protocol-level account of allocation concealment, adherence, treatment periods, or planned statistical analysis.
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.
Before assignment: Thirty subjects were enrolled, but one was removed from the study due to an adverse event, leading to 29 completers.
Overall Study
| Stage | Placebo First, Then Phendimetrazine | Phendimetrazine First, Then Placebo |
|---|---|---|
| STARTED | 15 | 15 |
| COMPLETED | 15 | 14 |
| NOT COMPLETED | 0 | 1 |
Reasons for not completing this period:
| Reason | Placebo First, Then Phendimetrazine | Phendimetrazine First, Then Placebo |
|---|---|---|
| Adverse Event | 0 | 1 |
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 | Study Completers |
|---|---|---|
| Participants analysed | 29 | |
| Age, Continuous | years | 46 (SD 4) |
| Sex: Female, Male: Female | Participants | 8 |
| Sex: Female, Male: Male | Participants | 21 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 21 |
| Race (NIH/OMB): White | Participants | 7 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 29 |
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 After at least seven days of maintenance placebo or target phendimetrazine dose.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | Cocaine Choices |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the number of times cocaine was selected when a monetary reward was available as an alternative. In the described modified progressive ratio procedure, participants made 10 choices between a portion of each available cocaine dose and US$0.25. The record states that reinforcing effects were measured for each cocaine dose during both phendimetrazine and placebo maintenance. The outcome is therefore intended to reflect choice behavior under the tested laboratory conditions, rather than simply whether cocaine was administered.
Choice frequency is relevant to the study question because selecting cocaine over money provides a behavioral measure of relative reinforcement in that task. This is a laboratory measure: it does not by itself measure longer-term substance use, treatment retention, or other clinical outcomes. The registry labels the endpoint as a continuous measure summarized by a mean and standard error, while its unit is “Cocaine Choices.” The results and the dose-specific values are not reported in the registry record. As a result, the endpoint’s observed level and the comparison between maintenance conditions cannot be interpreted from the posted results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a behavioral endpoint and describes how it was intended to be measured, but it does not report the endpoint values. There is no posted mean, standard error, condition-specific estimate, or comparison estimate for cocaine choices. The record lists one outcome measure and zero analyses. Consequently, the available information does not show whether choice frequency differed between placebo and phendimetrazine maintenance, how large any difference was, or how precisely it was estimated.
The outcome description covers each available cocaine dose during both maintenance conditions. However, the registry’s outcome status indicates that the primary outcome has several categories or time points and was not reduced to one comparison. No dose-specific results or condition-by-dose estimates are included. Without those results, the direction of a pattern across doses cannot be described, and a single overall effect cannot be inferred. The record also does not report a statistical test or confidence interval for the primary outcome.
For continuous data, a mean describes the average observed measurement, while a standard error describes the statistical precision of an estimated mean. A standard error is not a measure of how much individual participants vary. General interpretation of either statistic requires the actual estimate and its uncertainty; neither is available for this outcome in the registry record. A confidence interval, if reported, would describe a range of values compatible with the analysis and its assumptions. No confidence interval is reported.
The enrollment count of 30 should not be treated as the number analyzed for the primary endpoint. The registry does not report the outcome analysis denominator, completion by condition, or reasons data may be unavailable. Safety reporting lists 29 participants at risk in each of its two groups, but those group counts do not establish the primary-outcome sample size. The posted information therefore does not support a claim about the precision or representativeness of the behavioral comparison.
The study is marked completed, but completion status is not evidence that a particular result was obtained. Nor does a defined endpoint establish that an analysis was performed or reported. Conclusions should remain limited to what the record documents: a planned laboratory comparison of cocaine choice during maintenance conditions, without posted numerical primary-outcome results or analyses.
9. Statistical Methods Explained
What the design can address. The study is identified as randomized, triple-masked, and crossover. In general, randomization helps limit systematic differences in how study conditions are assigned. Masking can reduce the influence of expectations on participant behavior, study conduct, or outcome assessment. The registry does not identify which people were masked or describe the randomization and masking procedures, so their implementation cannot be assessed from this record.
In general, a crossover design exposes participants to multiple conditions and compares their measurements across those conditions. Because the same participant can contribute observations under different conditions, an analysis may account for within-participant dependence. Measurements from one participant are not necessarily statistically independent. The registry does not report the sequence assigned, period structure, washout, or statistical model, so it is not possible to determine how the crossover features were handled in analysis.
What the endpoint represents. The primary outcome counts how often cocaine was selected in a choice task with a monetary alternative. The described modified progressive ratio procedure used 10 choices between a portion of each available cocaine dose and US$0.25. The record says that reinforcing effects were measured for each cocaine dose under placebo and phendimetrazine maintenance. This behavioral measure addresses choice within the laboratory procedure; it is not a direct count of longer-term cocaine use or a measure of clinical recovery.
The outcome is classified as continuous and summarized using a mean and standard error. A mean is the arithmetic average of the measurements included in an analysis. The standard error reflects uncertainty in an estimated mean, under the analysis assumptions; it is distinct from the standard deviation, which describes spread among individual observations. The registry does not report the means, standard errors, sample sizes contributing to them, or the model used to obtain them.
General considerations for choice counts. A count outcome may have a distribution that differs from the symmetric distribution often assumed by basic methods for continuous data. General statistical practice considers the outcome’s range, distribution, repeated measurements, and potential clustering when choosing an analysis. Over-dispersion is a general concern when count data vary more than a chosen count model expects; ignoring it can lead to uncertainty estimates that are too small. These are general methodological considerations, not a description of the analysis used in this study. The registry record does not report a distributional model, diagnostics, transformation, or adjustment for within-participant dependence.
What a comparison would need to show. To interpret the primary question, readers would need estimates for cocaine choice under each maintenance condition, together with a clearly specified contrast and its uncertainty. A confidence interval is a general way to communicate the precision of an estimate: under its assumptions, it identifies values reasonably compatible with the observed data and analysis. A hypothesis test, if used, would address compatibility with a specified null hypothesis, but a p-value alone would not describe the magnitude or practical meaning of an effect. Neither a test nor a confidence interval is reported for the primary outcome.
The record lists zero analyses, and its outcome status says that several categories or time points were not reduced to one comparison. It does not report whether analyses were planned for individual cocaine doses, how repeated measurements were combined, or whether any model adjusted for period or sequence. It would be inappropriate to infer such choices from the crossover label or endpoint description.
Planning is not evidence of observed precision. Sample-size calculations are planning tools that depend on assumptions about the effect to detect, variability, allocation, and analysis. A planning illustration is not the same as an observed result or observed power. The registry does not report its own sample-size justification or a statistical plan. In the absence of the primary outcome estimates and analysis details, the precision of the study’s behavioral findings cannot be evaluated.
Reading the maintenance descriptions. The registry describes placebo maintenance and phendimetrazine maintenance, with the latter specified as up to 210 mg/day and twice-daily administration for approximately two weeks. The endpoint timeframe refers to testing after at least seven days of maintenance. The arm descriptions also state that acute cocaine and placebo were administered during placebo maintenance, including wording in the phendimetrazine arm description that refers to placebo maintenance. This leaves the acute administration sequence under the different maintenance conditions unclear. The record does not provide enough detail to resolve that ambiguity.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure, but its status indicates that the outcome has several categories or time points and was not reduced to one comparison. The description includes each available cocaine dose and both maintenance conditions. The record does not report how many dose-specific or condition-specific contrasts were planned, which comparison was primary for inference, or whether any multiplicity adjustment was used. Those details are not reported in the registry record.
Multiplicity matters in general when several comparisons are examined: the chance of at least one apparently unusual result can increase as the number of tests grows. Adjustments or a prespecified hierarchy can address that issue, but neither approach can be attributed to this study from the available record. With no posted endpoint results or analyses, it is also not possible to assess whether the reported outcome structure affected interpretation.
Missing-data procedures and analysis populations are not reported in the registry record. The record does not state the number randomized, the number with outcome measurements under each condition, how incomplete crossover participation was handled, or whether imputation or another missing-data method was used. The enrollment count of 30 is not an outcome-analysis denominator. The safety record lists 29 at risk in each group, but does not explain the difference between those counts and enrollment or establish who contributed primary-outcome data. Reasons for missing data, exclusions, and the handling of participants who did not complete all conditions are also not reported.
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 | 0 | 29 | 0.0% |
| Phendimetrazine | 0 | 29 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Placebo | 0 of 29 |
| Phendimetrazine | 0 of 29 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo | 0 of 29 |
| Phendimetrazine | 0 of 29 |
The registry lists two safety groups, Placebo and Phendimetrazine. For each group, 29 participants were recorded as at risk for serious adverse events and 29 as at risk for other adverse events. The recorded number affected was 0 in each group for both categories, and deaths were 0 in each group. These are the safety figures reported in the registry record.
A count of 0 means no events were recorded in that category for the listed group; it does not establish that the risk is absent. The record does not give adverse-event definitions, observation periods, ascertainment procedures, or details about the participants’ exposure during safety monitoring. It also does not explain why 29 participants were listed at risk when enrollment was 30. The safety counts should not be used as a substitute for primary-outcome results or as evidence about the comparative effect of the maintenance conditions on cocaine choice.
12. What the Result Does, and Does Not, Mean
The record documents a randomized, triple-masked crossover study intended to examine cocaine choice during placebo and phendimetrazine maintenance. Its primary behavioral measure is the number of choices of cocaine when money was available as an alternative. The described task used 10 choices and a monetary option of US$0.25. These details clarify the research question and the laboratory context in which the outcome was intended to be measured.
The record does not report the primary outcome values, an analysis, or an estimate comparing the maintenance conditions. Therefore, it does not establish whether cocaine choices were more frequent, less frequent, or similar under either condition. It also does not establish the magnitude or precision of a possible difference. The absence of posted numerical results should not be treated as evidence that the conditions were equivalent or that there was no effect.
The endpoint concerns behavior during a controlled laboratory choice task. Generalizing from such a measure to longer-term cocaine use or other clinical outcomes would require evidence beyond the endpoint definition. The registry record does not report those longer-term outcomes. Similarly, the study’s completed status does not supply missing estimates or resolve the ambiguity in the arm descriptions about acute administrations during maintenance.
The appropriate interpretation is limited: the registry describes a study designed to assess a behavioral measure across maintenance conditions, but the posted results do not permit a statistical conclusion about that measure. Safety counts are separately reported and should be read as recorded event counts, not as a substitute for the missing behavioral comparison.
13. Why This Trial Matters Statistically
This trial is statistically notable for the combination of a crossover design and a repeated behavioral choice outcome. In general, crossover studies can use within-participant comparisons, but those comparisons require attention to the dependence among repeated observations and to the sequence and timing of conditions. The registry identifies the crossover model without reporting how its sequence, period structure, or analysis was implemented. That makes the design label informative but insufficient to reconstruct the statistical comparison.
The endpoint is also measured across available cocaine doses and maintenance conditions. This creates an interpretive need to distinguish dose-specific patterns from any overall contrast. The registry marks the primary outcome as having several categories or time points, without reducing it to one comparison. No estimates or analyses are reported, so readers cannot determine how those repeated conditions were handled or whether the intended comparison was prespecified.
Finally, the record illustrates the difference between a clearly described measurement and a reported result. The choice task and summary measure are specified, but the values needed to assess direction, magnitude, and uncertainty are absent. Enrollment and safety counts do not replace the primary outcome estimates. For statistical interpretation, endpoint definitions, analysis details, denominators, and numerical results each answer different questions; the registry record supplies some design and measurement details, but not the primary outcome analysis.
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 main trial-specific limitation for interpretation is that the registry record does not report primary-outcome values or analyses. The endpoint is defined, but there is no reported mean, standard error, comparison estimate, or confidence interval. The outcome status also indicates that several categories or time points were not reduced to one comparison. These gaps prevent assessment of effect direction, magnitude, and precision.
The crossover designation does not provide the sequence of conditions, period structure, washout interval, or approach to repeated measurements. Randomization and triple masking are listed, but their procedures and the people masked are not described. The arm descriptions contain an ambiguity: the phendimetrazine arm refers to acute cocaine and placebo administration during placebo maintenance. The record does not clarify how acute testing related to phendimetrazine maintenance.
Enrollment was 30, while safety groups each list 29 participants at risk. The registry does not explain this difference, report the outcome-analysis denominator, or describe missing-data handling or analysis populations. It also does not report a sample-size justification or a statistical analysis plan. These omissions limit evaluation of the study’s precision and the credibility of any unreported comparison.
The Phase 1 inpatient human laboratory setting and choice-task endpoint describe a specific behavioral context. The primary measure is not a report of longer-term cocaine use or other clinical outcomes. The registry record does not report such outcomes, so findings from this task, even if available, would need to be interpreted within its defined scope.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Reinforcing Effects of Cocaine During Phendimetrazine Maintenance — NCT02522325.
- Registry record last updated 2019-07-02; status last verified 2019-06.
- Results first posted 2019-07-02.
- 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 NCT02522325, a completed Phase 1 randomized, triple-masked crossover study with enrollment of 30. It concerns Cocaine Use Disorder and compares behavioral testing during placebo and phendimetrazine maintenance in an inpatient human laboratory setting. Phendimetrazine maintenance is described as oral, twice daily, for approximately two weeks, up to 210 mg/day.
The primary endpoint is the number of times cocaine was selected over US$0.25 in a modified progressive ratio procedure involving 10 choices. The outcome is described as a mean with standard error and measured after at least seven days of maintenance. The registry lists one outcome measure and zero analyses, and does not report its numerical results. Safety reporting lists 29 at risk in each group, with 0 serious events, 0 other adverse events, and 0 deaths recorded in each group. Analysis populations, missing-data procedures, and a statistical analysis plan are not reported in the registry record.