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 Cyclobenzaprine Extended Release (ER) for Fibromyalgia (NCT01041495), a randomized phase 4 study. The primary outcome is Visual Analogue Pain Scale at 8 Weeks Post Treatment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01041495 |
| Phase | Phase 4 |
| Condition | Fibromyalgia, Pain, Sleep |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 37 |
| Arms in the primary outcome | 2 |
| Lead sponsor | State University of New York - Upstate Medical University |
| Results posted | Yes |
2. Clinical Question
Population
The registry concerns people with fibromyalgia, pain, sleep concerns, or fatigue. The registry record does not report the primary outcome population in further detail, such as eligibility criteria or baseline clinical characteristics. Enrollment was 37.
Intervention
The intervention was cyclobenzaprine extended release, identified in the record as Amrix. The study description frames it as augmentation for fibromyalgia fatigue and muscle pain. The dosing schedule and treatment duration are not reported in the registry record's posted outcome details.
Comparator
The comparator was placebo. The record identifies a randomized, parallel-group comparison, but does not report the allocation ratio or further details about how the placebo was administered.
Primary question
The primary endpoint was the Visual Analogue Pain Scale at 8 weeks. The endpoint description defines it as change from baseline in subjective pain on a 10-point scale, with higher scores worse. The statistical question is whether the posted pain outcome differed between the cyclobenzaprine ER and placebo groups. The record reports a two-sided t-test for a mean difference in final values, so the analysis label does not explicitly match the endpoint description's change-from-baseline wording.
3. Trial Design
The registry describes a randomized, triple-masked, parallel-group phase 4 study sponsored by State University of New York - Upstate Medical University. The study title describes an eight-week, double-blind efficacy study of cyclobenzaprine ER augmentation for fibromyalgia fatigue and muscle pain. The masking descriptor in the registry is triple, while the title says double-blind; which people or roles were masked is not reported in the registry record.
The recorded start was 2009-06, and primary completion was 2013-03. The study status is terminated. The reason for termination and the circumstances surrounding it are not reported in the registry record. Registered enrollment was 37. The arm-level primary outcome summaries list 16 for cyclobenzaprine ER and 12 for placebo; the registry does not explain the relation between those outcome counts and registered enrollment.
The primary endpoint was the Visual Analogue Pain Scale at 8 weeks. The registry also lists Brief Fatigue Inventory and Fibromyalgia Impact Questionnaire outcomes at 8 weeks. It records 3 outcome measures and 5 analyses. The specific protocol, allocation procedure, planned enrollment rationale, dose, adherence information, and treatment discontinuation details are not reported in the registry record.
Randomization is intended to reduce systematic differences between groups at assignment, while masking can limit some forms of bias in treatment delivery, assessment, or interpretation. Those are general design principles, not confirmation of how this study implemented them. The registry does not describe the randomization sequence, concealment process, or masking procedures in enough detail to assess those features.
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: subjects had to meet eligibility criteria
Overall Study
| Stage | Cyclobenzaprine ER | Placebo |
|---|---|---|
| STARTED | 16 | 12 |
| COMPLETED | 12 | 5 |
| NOT COMPLETED | 4 | 7 |
Reasons for not completing this period:
| Reason | Cyclobenzaprine ER | Placebo |
|---|---|---|
| Withdrawal by Subject | 2 | 5 |
| Adverse Event | 2 | 1 |
| Lost to Follow-up | 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 | Cyclobenzaprine ER | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 16 | 12 | 28 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 16 | 12 | 28 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 15 | 10 | 25 |
| Sex: Female, Male: Male | Participants | 1 | 2 | 3 |
| Region of Enrollment: United States | participants | 16 | 12 | 28 |
6. Primary Endpoint
The registry lists the primary outcome as Visual Analogue Pain Scale at 8 Weeks Post Treatment, measured over 8 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the Visual Analogue Pain Scale at 8 weeks. The registry describes it as change from baseline in subjective pain, measured on a 10-point scale, where 1 means no pain and 10 means severe pain. Higher scores are worse. A pain scale is used to represent a participant's subjective experience in a form that can be compared across groups and assessed statistically. It does not turn pain into an objective measurement; it records a scored report of experience.
The endpoint's stated timeframe is 8 weeks. That timing fits the study's stated eight-week focus, but the registry record does not report whether any additional pain assessments were made or how those assessments were used. The primary outcome population field is blank.
The posted analysis is labeled a mean difference in final values, whereas the endpoint description says change from baseline. The registry record does not explain this wording difference. Interpretation therefore depends on the analysis actually performed and on whether the reported values represent final scores or changes. The record does not supply enough detail to resolve that point. It also does not report a confidence interval for the stated mean difference.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome values are 4.8 for cyclobenzaprine ER and 5.7 for placebo. The recorded ranges are 4.0 to 6.0 and 5.0 to 6.0, respectively. The outcome description says higher scores are worse, but also defines the endpoint as change from baseline. Because the reported analysis is labeled as a mean difference in final values, the record does not clarify whether the arm values are final scores or changes. The numbers should therefore be read with that ambiguity in mind.
The sponsor's reported analysis is a two-sided t-test, with a stated mean difference of .869 and p = .869. No confidence interval is reported. A p-value describes how compatible the observed data are with a specified null model under the assumptions of the test; it is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The absent confidence interval limits assessment of the range of effect values compatible with the data under the analysis.
The values in the two arms are descriptive summaries. A difference between group summaries alone does not establish that the intervention caused an outcome difference. Interpretation also depends on the analysis population, missing outcome data, outcome definition, and statistical assumptions. Those details are not fully described in the registry record.
The registry reports an outcome count of 16 in the cyclobenzaprine ER group and 12 in the placebo group. These are the counts attached to the posted outcome summaries, not a statement about every participant enrolled or the reason for any difference between enrollment and outcome counts. The record does not explain missingness or report how participants without endpoint data were handled.
The study status is terminated, but the reason is not reported in the registry record. Termination alone does not establish why the trial ended or whether it changed the analysis. The record also does not report a prospective statistical analysis plan, an interim analysis plan, or a rationale for the enrollment target. Overall, the posted result is limited by incomplete reporting about the endpoint's analyzed form and by the lack of a confidence interval and analysis-population details.
9. Statistical Methods Explained
Statistical methods are useful only when their target and assumptions are clear. The registry identifies a two-sided t-test and labels its estimand as a mean difference in final values. It does not describe the test implementation, the analysis population, or a fuller model specification. The explanation below gives general statistical context and distinguishes it from details established by the registry record.
What does a two-sided t-test assess?
In general, a t-test compares a mean difference with the variability expected under a null model in which the population means are equal. A two-sided test allows departures in either direction, rather than testing only for a larger or smaller value in a prespecified direction. The reported p-value is .869. It is evidence evaluated under the test's assumptions, not a probability that the treatment works or that the null model is true. The registry does not report the prespecified significance threshold for this analysis, so the test result should not be characterized by assuming an unreported decision rule.
A t-test relies on assumptions about the sampling process and the distribution or behavior of the estimated mean difference. The registry does not report diagnostic checks, a variance assumption, adjustments, or a sensitivity analysis. This does not show that assumptions were violated; it means the record does not allow a reader to assess them.
What does the reported mean difference represent?
A mean difference describes a contrast between group averages. Its interpretation depends on which outcome values were compared and how the contrast was signed. Here, the analysis is labeled as a mean difference in final values, while the endpoint description defines a change from baseline. The stated value is .869, but the registry does not explain the discrepancy in terminology or provide enough detail to determine the exact construction and sign convention. The group summaries are 4.8 and 5.7, with full ranges of 4.0 to 6.0 and 5.0 to 6.0. The reported analysis value should not be reconstructed from these summaries because the record does not give the necessary analysis detail.
Why does a confidence interval matter?
In general, a confidence interval conveys uncertainty around an estimated effect: it gives a range of values compatible with the data and the interval procedure under its assumptions. It can help distinguish a relatively precise estimate from one that remains uncertain. No confidence interval is reported for the mean difference in the registry analysis. The posted full ranges are descriptive ranges of observed values, not confidence intervals for the group difference. They do not serve as a substitute for an interval estimate of the treatment contrast.
How should the endpoint wording be read?
The endpoint description says the measure is change from baseline through week 8, and states that higher scores are worse. The analysis label instead says final values. Final-score comparisons and change-score comparisons are not interchangeable descriptions, even if they may sometimes be related in a particular analysis. The registry does not say whether baseline values were included as covariates, whether the analysis used change scores, or whether the reported arm values are baseline-adjusted. Those details are not reported in the registry record.
The outcome uses a subjective pain scale. In general, patient-reported measures capture experiences that may not be directly measurable by an instrument or observer. Their usefulness depends on consistent administration, clear scoring, and complete collection. The record gives the scale anchors and direction but does not report administration procedures or validation details for this specific use.
What do the planning assumptions mean?
The planning illustration is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It varies the effect to detect as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study had a particular power or that an effect was detected. Sample-size calculations based on an observed estimate are illustrative and can be unstable when that estimate is imprecise. The registry record does not report the trial's own sample-size justification, so the illustration cannot be treated as the prospective design rationale. No planning output values are stated in the registry record.
The stated analysis is a mean comparison, not a model for repeated measurements or time-to-event outcomes. The registry does not report whether the analysis accounted for baseline measures, site, or other covariates. It also does not describe the treatment of missing outcomes, protocol deviations, or departures from the assigned treatment. Those omissions limit independent appraisal of the analysis, but do not establish that any particular method was or was not used.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| t-test, 2 sided | Mean Difference (Final Values) .869 | not reported | 0.869 |
The registry reports the sponsor's primary analysis as a two-sided t-test of the mean difference in final values. The stated mean difference is .869, and the reported p-value is .869. A confidence interval is not reported. The registry does not give further details about the test or clarify the difference between the analysis label's final values and the endpoint description's change from baseline.
A recalculation from posted group summaries is an unadjusted calculation and is not the same thing as the sponsor's analysis, which may use information or procedures not represented in a short summary. The registry record does not state a recalculated estimate or interval in the registry record for the posted result, so no numerical comparison between a recalculation and the sponsor's estimate can be made. The registry does not indicate a discrepancy between the sponsor analysis and a recalculation.
When a discrepancy is identified, the sponsor's own analysis takes precedence for describing the trial's reported analysis, while any recalculation should be clearly treated as a check based on summary data rather than a replacement for the trial analysis. In this case, the available record supports reporting the sponsor's stated test and its limits, not inferring unreported analytic details or treating an unadjusted calculation as the trial's prespecified result.
11. Multiplicity, Missing Data and Analysis Populations
The registry lists 3 outcome measures, including the primary pain outcome and secondary outcomes for the Brief Fatigue Inventory and Fibromyalgia Impact Questionnaire at 8 weeks. It also records 5 analyses. Testing more than one outcome or performing multiple analyses can raise a multiplicity concern: in general, as the number of statistical tests increases, the chance of at least one apparently notable result can increase if no adjustment or other control is used.
The registry record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a strategy for interpreting multiple analyses. It also does not report whether the outcomes and analyses were all specified before data were examined. The absence of those details does not establish that no plan existed; it means the record does not allow the approach to be assessed. Values are missing or not estimable for a two-arm comparison for another endpoint, according to the registry's outcome note. That limitation means the available record does not support a complete reading of all listed outcomes.
The primary outcome population field is blank. The analysis population, such as whether all randomized participants were included or another defined group was used, is not reported in the registry record. Neither are the number of participants with missing endpoint observations by reason, the method used to handle missing data, or sensitivity analyses for missingness. The posted group counts for the primary outcome are 16 and 12, while registered enrollment is 37; the registry does not explain the relation between those figures. They should not be used to infer reasons for missing outcomes or the analysis population.
These omissions matter because the results can depend on which participants contribute data, how incomplete observations are handled, and how multiple outcomes are interpreted. They limit the ability to determine how robust the reported analysis is to alternative choices. No assumptions about missingness, interim analyses, or statistical planning beyond the listed planning illustration are justified by the registry record.
12. 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 |
|---|---|---|---|
| Cyclobenzaprine ER | 0 | 16 | 0.0% |
| Placebo | 0 | 12 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Cyclobenzaprine ER | 2 of 16 |
| Placebo | 1 of 12 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Cyclobenzaprine ER | Placebo |
|---|---|---|---|
| glucosemia | Endocrine disorders | 0 of 16 | 1 of 12 |
| Fatigue | General disorders | 1 of 16 | 0 of 12 |
| dizziness | General disorders | 1 of 16 | 0 of 12 |
The registry reports serious adverse events affecting 0 of 16 participants at risk in the cyclobenzaprine ER group and 0 of 12 at risk in the placebo group. No top serious adverse event terms are listed. The death counts are not reported in the registry record; an unreported value is not the same as a recorded count of zero.
Other adverse events are reported as affecting 2 of 16 participants at risk in the cyclobenzaprine ER group and 1 of 12 at risk in the placebo group. The record does not provide the event terms in these summaries, severity, timing, or whether events were judged related to treatment. These counts describe participants affected as recorded; they do not provide a full account of event frequency, recurrence, or clinical significance.
Safety comparisons require context, including definitions, ascertainment procedures, observation time, and completeness of reporting. Those details are not reported in the registry record. The small outcome and safety group counts also make the summaries descriptive rather than a basis for broad conclusions about uncommon harms. The reported absence of serious adverse events in these group summaries should not be interpreted as proof that serious events cannot occur.
13. What the Result Does, and Does Not, Mean
The registry presents a randomized comparison of cyclobenzaprine ER and placebo, with pain at 8 weeks as the primary endpoint. It reports group values of 4.8 and 5.7, full ranges of 4.0 to 6.0 and 5.0 to 6.0, and a sponsor-reported two-sided t-test with a stated mean difference of .869 and p = .869. No confidence interval accompanies that analysis. The endpoint description says higher scores are worse, but the record does not clarify whether the reported values are final scores or changes from baseline.
These registry entries describe what the registry reports; they do not establish a causal treatment effect or its clinical importance. A p-value alone does not convey the precision of an estimate, and the missing confidence interval leaves uncertainty about the range of effects compatible with the analysis unquantified in the record. The lack of detail about analysis populations and missing data further limits interpretation.
The trial's status is terminated. The reason for termination is not reported in the registry record and should not be inferred from the status. Similarly, the posted summaries do not establish why outcome counts differ from registered enrollment, or whether any missing observations were related to treatment or outcome.
General interpretation of a trial also considers protocol details, participant characteristics, treatment implementation, and the prespecified analysis plan. Much of that information is not reported in the registry record. The findings should therefore be read as a limited account of the posted outcome summaries and sponsor analysis, not as a complete assessment of efficacy, safety, or applicability to other populations.
14. Why This Trial Matters Statistically
This trial is statistically notable as a registry record with a randomized, triple-masked, parallel-group design and a subjective pain endpoint, but with limited detail about the analysis behind its reported result. The record's endpoint description emphasizes change from baseline, whereas the analysis is labeled a mean difference in final values. That distinction affects what the contrast represents and makes clear outcome definitions important for reproducibility.
The sponsor analysis reports a mean difference and p-value but no confidence interval. This illustrates why a test result alone is an incomplete account of an estimated effect. A confidence interval can communicate precision, while the estimate's definition and analysis population explain what the interval refers to. The full observed ranges do not replace an interval for the group contrast.
The record also illustrates the importance of distinguishing enrollment from the number contributing to an outcome summary. Enrollment is 37, while the primary outcome summaries list 16 and 12. Without a participant-flow account or missing-data description, a reader cannot identify the reason for that difference or assess the consequences for analysis.
Finally, the registered status is terminated, but no reason is reported. The status and the posted results should be interpreted separately: the status does not explain the result, and the result does not explain the status. These reporting gaps are useful reminders that design labels and numerical outcomes must be read alongside definitions, analysis plans, participant flow, and uncertainty estimates.
15. 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 arise from the registry record. The primary outcome population field is blank, and the record does not describe eligibility criteria or baseline characteristics in the posted outcome details. This makes it difficult to assess who contributed to the analysis or how representative the analyzed group was.
The endpoint description defines change from baseline, but the reported analysis is labeled as a mean difference in final values. The record does not resolve this difference in wording. The reported group values and full ranges are available, but there is no confidence interval for the group contrast and no detailed model specification. The recorded p-value therefore cannot by itself convey the precision or clinical meaning of the estimated difference.
The record does not explain the relationship between enrollment of 37 and the primary outcome counts of 16 and 12. Reasons for missing endpoint data, missing-data handling, and sensitivity analyses are not reported. The analysis population and any departures from assigned treatment are also not described.
The record identifies 3 outcome measures and 5 analyses, but does not report a multiplicity strategy, a prespecified hierarchy, or a detailed statistical analysis plan. Although a planning illustration is described, the trial's own sample-size justification is not reported. The record also does not provide the reason for termination, detailed masking procedures, or the study's dosing schedule in the posted outcome details. These gaps restrict independent evaluation; they do not show that the unreported procedures were absent or that a particular bias occurred.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Cyclobenzaprine Extended Release (ER) for Fibromyalgia — NCT01041495.
- Registry record last updated 2024-11-27; status last verified 2024-11.
- Results first posted 2021-10-06.
- 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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19. Record Summary
NCT01041495 is a phase 4 randomized, triple-masked, parallel-group study of cyclobenzaprine ER versus placebo for fibromyalgia. The registry lists enrollment of 37 and a terminated status. The recorded start was 2009-06, and primary completion was 2013-03; the reason for termination is not reported.
The primary endpoint was the Visual Analogue Pain Scale at 8 weeks, described as change from baseline with higher scores worse. The posted group values are 4.8 for cyclobenzaprine ER and 5.7 for placebo. The sponsor analysis is a two-sided t-test labeled as a mean difference in final values, reporting .869 and p = .869; no confidence interval is reported. The endpoint wording and analysis label are not reconciled in the registry record.
Secondary outcomes concern fatigue and fibromyalgia impact. The record does not report the primary analysis population, missing-data approach, multiplicity strategy, or reason for termination. Safety summaries report no serious adverse events affecting participants in either group; death counts are not reported.