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 Efficacy and Safety of Gabapentin/B-complex Versus Pregabalin in Diabetic Peripheral Neuropathy Pain Management (NCT01364298), a randomized phase 4 study. The primary outcome is Change From Baseline in Average Numeric Pain Intensity Scale (NPIS) Score at Day 84.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01364298 |
| Phase | Phase 4 |
| Condition | Diabetic Peripheral Neuropathic Pain |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 353 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Merck KGaA, Darmstadt, Germany |
| Results posted | Yes |
2. Clinical Question
The trial asks whether pain intensity changes over the study period among participants with diabetic peripheral neuropathic pain treated with gabapentin/B-complex or pregabalin. It is a randomized, open-label comparison: treatment was assigned at random, while masking was absent. The primary outcome is change from baseline in average Numeric Pain Intensity Scale (NPIS) score at Day 84 (Week 12).
Population
The condition listed is diabetic peripheral neuropathic pain. The primary outcome description identifies the analysis population as the per protocol population: treated participants who had no major protocol violations, met study inclusion criteria, and complied with proper administration of study drug. The registry record does not report the evaluable participant count for the primary outcome.
Intervention
Gabapentin/B-complex. The registry record identifies this as a drug intervention but does not provide arm-specific dosing or administration details in the arm description.
Comparator
Pregabalin, also identified as a drug intervention. The arm description does not report dosing or administration details.
Primary question
How does average pain intensity change from baseline to Day 84 in the per protocol population assigned to each treatment? The registry record gives the outcome definition but does not report treatment-group means, a between-group estimate, or an inferential result for this comparison.
The trial is described as multicenter, randomized, parallel-group, and Phase IV, with enrollment listed as 353. Its open-label design means participants and study personnel were not masked to assigned treatment. The registry record does not report the randomization procedure or whether outcome assessment was masked.
3. Trial Design
This was a multicenter, randomized, open-label, parallel-group, Phase IV study comparing gabapentin/B-complex with pregabalin for diabetic peripheral neuropathic pain management. The registry lists enrollment as 353 and the trial status as completed. The listed start is 2011-04, and the primary completion is 2012-07. The sponsor is Merck KGaA, Darmstadt, Germany.
Random allocation is intended to create treatment groups that are comparable on average with respect to both measured and unmeasured characteristics. It does not guarantee that the groups are identical, particularly in a particular trial. The registry record identifies the allocation as randomized but does not report the sequence-generation method, allocation concealment, or the allocation ratio. Equal allocation is an assumption used in the separate planning illustration, not a reported feature of the actual trial design.
The parallel-group structure means participants were assigned to a treatment group rather than being described as crossing between treatments. The record does not provide arm-level descriptions beyond the intervention names. In particular, dosing, treatment duration details beyond the primary assessment timing, adherence procedures, and concomitant-treatment rules are not reported in the registry record.
Open-label conduct is relevant because knowledge of treatment assignment can affect behavior, symptom reporting, clinical decisions, and assessment. That possibility is especially pertinent to a patient-reported pain score. Randomization can address some sources of group difference, but it does not remove potential effects of unmasked treatment knowledge. The registry record does not report additional procedures designed to limit such effects.
The primary outcome was measured at baseline and Day 84 (Week 12). The primary outcome description specifies a per protocol population, rather than describing the primary analysis as including every randomized participant. The record does not report a participant flow, reasons for exclusion from this population, or the number evaluable in each arm. The registry record also does not report a protocol, a sample-size justification for the trial, or interim analyses.
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 | Gabapentin/B-complex | Pregabalin |
|---|---|---|
| STARTED | 176 | 177 |
| Treated | 174 | 174 |
| COMPLETED | 162 | 154 |
| NOT COMPLETED | 14 | 23 |
Reasons for not completing this period:
| Reason | Gabapentin/B-complex | Pregabalin |
|---|---|---|
| Adverse Event | 3 | 4 |
| Lack of adherence to treatment | 1 | 3 |
| Lack of Efficacy | 1 | 0 |
| Lost to Follow-up | 5 | 10 |
| Withdrawal by Subject | 3 | 3 |
| Other | 1 | 3 |
Analysis population for the primary outcome, as defined in the registry: Per protocol population (PPP) included all the treated participants who showed no major protocol violations and were compliant with study inclusion criteria and with the proper administration of the study drug. 'n' signifies number of participants who were evaluable for specified categories at different time points.
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.
Population: Safety population included all the randomized participants who received at least one dose of study drug.
| Characteristic | Unit | Gabapentin/B-complex | Pregabalin | Total |
|---|---|---|---|---|
| Participants analysed | 174 | 174 | 348 | |
| Age, Continuous | years | 53.2 (SD 10.5) | 54.3 (SD 9.4) | 53.8 (SD 9.9) |
| Sex: Female, Male: Female | Participants | 119 | 109 | 228 |
| Sex: Female, Male: Male | Participants | 55 | 65 | 120 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Average Numeric Pain Intensity Scale (NPIS) Score at Day 84, measured over Baseline and Day 84 (Week 12).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in average NPIS score at Day 84 (Week 12). NPIS is an 11-point scale, with 0 representing no pain and 10 representing the worst possible pain. Participants were asked to mark the number that best represented their current pain level over the previous 24 hours. The reported average pain score was based on daily average records for the past seven days.
The endpoint is a continuous measure: it records a value along a numerical scale rather than assigning each participant to a simple event category. A change score describes how a participant’s measured value differs between baseline and follow-up. In this record, change was defined as baseline value minus the value at Day 84. Under that definition, a positive change corresponds to a lower Day 84 pain score than baseline, while a negative change corresponds to a higher Day 84 score. This explains the direction of the measure; it does not establish what change occurred in either treatment group.
Using a follow-up score in relation to baseline can focus the comparison on symptom change over the trial period. The average is intended to represent pain across the recorded days rather than a single moment alone. The registry record does not provide group-level endpoint results, the standard deviations, or a between-group estimate. It therefore does not establish the size or precision of any treatment contrast on this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the outcome of interest and the scheduled assessment, but the registry entries available for this analysis do not include the primary outcome values for either treatment group. There is no reported group mean change, standard deviation, between-group difference, confidence interval, or p-value. The record also lists no analysis entries. Consequently, the primary endpoint cannot be interpreted as showing a particular direction, magnitude, or statistical precision of difference between gabapentin/B-complex and pregabalin.
This distinction matters because knowing the endpoint definition is not the same as knowing its result. A treatment-group comparison requires outcome data and a clearly identified contrast. The registry record says the endpoint is mean change in NPIS score, but it does not give the numerical estimates needed to judge how the groups changed or how far apart they were. A result cannot be inferred from the trial title, the stated objective, or the fact that enrollment was listed.
The primary outcome description defines the analysis population as the per protocol population. That population includes treated participants without major protocol violations who met inclusion criteria and complied with proper study-drug administration. The record does not provide arm-specific evaluable counts or explain how participants who did not meet these conditions were handled. A per protocol result, if reported, would describe the selected population meeting those criteria; it would not automatically be equivalent to an analysis of everyone randomized.
Selected adverse-event counts are reported separately. For serious adverse events, the listed counts are 1 among 174 at risk in the gabapentin/B-complex group and 0 among 174 at risk in the pregabalin group. For other adverse events, the listed counts are 79 among 174 at risk and 93 among 174 at risk, respectively. These are descriptive counts, not evidence by themselves of a reliable difference in safety. The record does not provide a comparative statistical analysis for these counts, and a zero reported count in one group does not establish that an event is impossible or that there is no risk.
The record lists cerebrovascular disorder as a top serious-event term at 0.6%, but does not identify the treatment group for that term in the registry record. Death counts are not reported in the registry record. The safety information therefore has limited detail for evaluating event types, comparative risks, or uncertainty.
Overall, the registry record supports a description of the trial design, primary outcome definition, and selected adverse-event counts. It does not report the primary efficacy estimates needed to quantify the comparison. Any interpretation of comparative pain change or a statistical test of that difference would go beyond the reported results.
9. Statistical Methods Explained
Statistical methods determine how trial observations are converted into estimates and how uncertainty around those estimates is described. The registry record identifies a mean continuous primary outcome and a per protocol population, but it does not report the method used to compare groups, the numerical outcome estimates, or the uncertainty estimates. The explanations below describe general statistical concepts; they should not be read as a claim that a particular unreported procedure was used in this trial.
What does a mean change represent?
A mean is an average across the participants whose observations contribute to an analysis. For an individual, the endpoint is defined as baseline NPIS score minus the Day 84 score. A group mean change would summarize those individual changes for the participants included in that group’s analysis. It is not the same as the score of a typical individual, and it can be affected by unusually large or small changes. A standard deviation describes how spread out individual observations are around a group mean. It describes variability among observations, not uncertainty in the estimated mean itself.
To compare randomized groups, an analysis may estimate a difference between their mean changes. The interpretation depends on the order used to subtract one group from the other, so the sign needs to be defined before describing which group has the higher estimate. The registry record does not report a between-group estimate or its sign convention. It is therefore not possible to state the size or direction of a group contrast.
What does a confidence interval communicate?
In general, a confidence interval gives a range of values compatible with an estimate under the assumptions of the statistical method. A narrow interval indicates greater precision than a wide interval, while an interval spanning a broad range leaves more uncertainty about the size and direction of the effect. An interval is not a guarantee that the true value lies within that particular range, and it does not replace interpretation of the outcome scale or the study design. No confidence interval for the primary comparison is reported in the registry record.
A p-value, when used, summarizes how incompatible the observed data are with a specified null hypothesis under the assumptions of the test. It does not measure the probability that a treatment is effective, the size of a treatment effect, or the probability that chance alone produced the result. A p-value also does not show whether an estimate is precise or clinically important. The registry record does not report a p-value for the primary comparison or identify a test used for it.
How should the planning illustration be understood?
The record describes a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. For non-time-to-event outcomes, the planning quantities are expressed as participants per arm; time-to-event planning quantities are expressed as total events using the Schoenfeld approach. These are planning assumptions, not evidence about the number of participants actually observed in an analysis.
A planning calculation asks what sample size would be needed under its assumptions to detect a specified effect with a chosen operating characteristic. Its output is not the probability that this completed trial detected an effect, and it is not observed power. The registry record does not report the numerical outputs of the planning illustration in the registry record. It also does not report a trial-specific sample-size justification or show that the illustration’s assumptions formed part of the original design.
General power calculations depend on assumptions about the effect size, variability, significance level, allocation, and analysis. If any of these differ from the assumptions used in planning, the calculated sample requirement may not describe the actual study. Choosing a fraction of an observed effect also makes the illustration dependent on that observed estimate, which may itself be uncertain. The illustration should therefore be read as a planning exercise, not a substitute for the trial’s reported estimates and uncertainty.
Why can over-dispersion matter?
For count outcomes, a statistical model may assume a particular relationship between the average count and its variability. Over-dispersion means the observed variation is greater than the model expects. If it is ignored, standard errors can be too small and confidence intervals too narrow, potentially making results appear more precise than they are. This is a general issue for count data, not a reported finding about this trial. The primary outcome is described as a mean continuous measure, and the registry record does not report the statistical model used for it.
For adverse events, a count of participants with an event is not the same as a model-based comparison. A comparative analysis may need to account for the number of participants at risk, the event definition, follow-up, and the precision of the estimate. The listed adverse-event counts do not include a reported comparative model or uncertainty interval. It would be inappropriate to infer either from the counts alone.
Interpretation also depends on the analysis population and the handling of missing outcome observations. The primary outcome description names a per protocol population, but the registry record does not describe imputation, assumptions about missingness, or sensitivity analyses. These details can affect the meaning and robustness of an estimate, so their absence limits methodological appraisal.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one primary outcome and 9 secondary outcome measures. The secondary outcomes include changes in LANSS and VAS scores at Day 84, POMS score, sleep evaluation, patient and clinical global impression measures, improvement thresholds on NPIS, and adverse events. Testing several outcomes or several categories and time points can increase the chance of observing at least one nominally notable result by chance. Statistical plans sometimes address this through a prespecified hierarchy or adjustment, but the registry record does not report whether any multiplicity procedure was planned or used.
The primary outcome description concerns change in average NPIS score at Day 84 (Week 12). The record indicates that the primary outcome has several categories or time points and is not reduced to one comparison. It does not report a single analysis estimate or a set of category-specific results in the registry record. The record lists no analysis entries, so it does not establish which comparisons were made or how multiple comparisons were handled.
Missing-data methods are also not reported in the registry record. There is no description of the extent or pattern of missing primary outcome observations, the assumptions used to address missing values, or sensitivity analyses assessing those assumptions. The primary outcome population is described as per protocol, but the number evaluable by arm and the reasons participants may have been excluded are not reported. Without these details, the effect of missing observations or population selection cannot be assessed.
These omissions do not show that a particular method was or was not used outside the registry record. They mean that the posted information does not allow readers to evaluate multiplicity control, missing-data handling, or the consequences of the per protocol definition.
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 |
|---|---|---|---|
| Gabapentin/B-complex | 1 | 174 | 0.6% |
| Pregabalin | 0 | 174 | 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 |
|---|---|
| Gabapentin/B-complex | 79 of 174 |
| Pregabalin | 93 of 174 |
Most frequent serious adverse event terms
| Event term | Organ system | Gabapentin/B-complex | Pregabalin |
|---|---|---|---|
| Cerebrovascular disorder | Nervous system disorders | 1 of 174 | 0 of 174 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Gabapentin/B-complex | Pregabalin |
|---|---|---|---|
| Somnolence | Nervous system disorders | 41 of 174 | 52 of 174 |
| Dizziness | Nervous system disorders | 32 of 174 | 52 of 174 |
| Headache | Nervous system disorders | 14 of 174 | 13 of 174 |
| Vertigo | Ear and labyrinth disorders | 1 of 174 | 11 of 174 |
| Diarrhoea | Gastrointestinal disorders | 5 of 174 | 6 of 174 |
| Urinary tract infection | Infections and infestations | 2 of 174 | 8 of 174 |
| Nausea | Gastrointestinal disorders | 1 of 174 | 5 of 174 |
| Gait disturbance | General disorders | 0 of 174 | 6 of 174 |
| Insomnia | Psychiatric disorders | 1 of 174 | 4 of 174 |
| Oedema | Metabolism and nutrition disorders | 2 of 174 | 3 of 174 |
Serious events with the highest arm-level rate: cerebrovascular disorder (0.6%).
The registry record lists serious adverse events among 1 of 174 participants at risk in the gabapentin/B-complex group and 0 of 174 participants at risk in the pregabalin group. For other adverse events, the listed counts are 79 of 174 and 93 of 174, respectively. These are counts of participants, not a complete description of event severity, timing, duration, or recurrence. The record does not report a comparative statistical analysis or confidence intervals for these figures.
A count of zero means that no event of the specified type was recorded in the listed group in the reported data; it does not establish that the underlying risk is zero. Likewise, the difference between two observed counts cannot by itself show whether a treatment caused more or fewer events. Interpretation would depend on the event definitions, follow-up and ascertainment, participant characteristics, and uncertainty around the estimates.
Cerebrovascular disorder is listed as a top serious-event term at 0.6%, but the treatment group associated with that term is not identified in the registry record. Death counts are not reported in the registry record. The safety figures therefore provide a limited descriptive snapshot, not a comprehensive comparative assessment of safety.
12. What the Result Does, and Does Not, Mean
The available record establishes that this was a randomized, open-label, parallel-group Phase IV comparison of gabapentin/B-complex and pregabalin for diabetic peripheral neuropathic pain. It also defines a primary pain-intensity endpoint: mean change from baseline in average NPIS score at Day 84 (Week 12), evaluated in a per protocol population. These details clarify what the trial set out to compare and how the primary outcome was defined.
The registry record does not report the group-level primary outcome values, a between-group estimate, its uncertainty, or a p-value. Therefore, the posted information does not show how much pain scores changed in either group or whether the groups differed on the primary endpoint. The absence of those results in the registry record is not evidence that the treatments had the same effect, nor does it establish that one had a larger effect.
The listed adverse-event counts can be read descriptively, with the limitations of sparse detail and no reported comparative analysis. They do not establish causation, quantify comparative safety precisely, or demonstrate that an event cannot occur when a zero count is listed. The record also does not report death counts.
More broadly, randomization supports a fair comparison when the trial is analyzed according to an appropriate prespecified plan, but the record does not describe enough of the analysis to assess that plan. The open-label design is relevant for a patient-reported endpoint, and the per protocol population may not represent everyone randomized. Missing-data handling, multiplicity procedures, and treatment-group outcome counts are not reported in the registry record.
The appropriate conclusion is limited: the record documents the design, outcome definition, and selected safety counts, but it does not provide enough primary efficacy results to estimate the comparative pain outcome or its precision. No conclusion about whether either treatment works or does not work follows from the information.
13. Why This Trial Matters Statistically
This trial raises several useful statistical issues for clinical researchers. First, a randomized design and a clearly defined endpoint are important, but readers also need the actual group estimates and their uncertainty to interpret a comparison. A named primary outcome alone does not show the result. Here, the record specifies mean change in average NPIS score at Day 84 (Week 12), yet does not report the treatment-group estimates or a between-group contrast.
Second, the analysis population matters. The primary outcome is described for a per protocol population of treated participants meeting compliance and protocol criteria. That definition focuses on a selected set of participants. Without arm-specific evaluable counts, participant flow, and a clear account of exclusions, readers cannot judge how that population relates to everyone randomized or how selection may affect interpretation.
Third, the open-label design deserves attention because pain is reported by participants and treatment knowledge can influence reporting or behavior. Randomization remains an important design feature, but it does not remove every possible influence of knowing treatment assignment. Statistical interpretation should take the outcome’s measurement process and the design together.
Finally, the record lists multiple secondary outcomes and selected adverse-event counts, while not reporting multiplicity procedures, missing-data methods, or inferential results. Those omissions illustrate why statistical reporting should include prespecified comparisons, estimates, confidence intervals, population counts, and transparent analysis details. These elements help distinguish a meaningful estimate from a bare count or an outcome label. The trial is thus a useful example of how an informative design description can coexist with insufficient posted results for a precise 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.
The primary limitation for interpreting comparative efficacy is that group-level primary endpoint results are not reported in the registry record. There is no reported mean change by arm, between-group estimate, standard deviation, confidence interval, or p-value. As a result, neither the magnitude nor the precision of the primary comparison can be assessed from the posted information.
The record identifies the per protocol population but does not provide its evaluable count by arm, participant flow, or reasons for exclusion. It also does not report an analysis of all randomized participants. Missing-data extent and handling, including any sensitivity analyses, are not reported in the registry record. These details are needed to understand how the analyzed participants relate to the randomized groups and how incomplete measurements may affect an estimate.
The open-label design is a further consideration for a patient-reported pain outcome. The record identifies masking as absent but does not report whether any outcome assessment procedures were masked. Treatment dosing and detailed arm procedures are also not reported in the registry record, limiting assessment of treatment exposure and adherence beyond the per protocol description.
The registry lists 9 secondary outcome measures and notes that the primary outcome has several categories or time points rather than a single reduced comparison. It does not report a multiplicity strategy or specific analysis entries. The listed serious and other adverse-event counts are descriptive and lack reported comparative uncertainty; the serious-event term at 0.6% is not assigned to an arm in the registry record. Death counts are not reported in the registry record.
Finally, enrollment is listed as 353, but the record does not explain the difference, if any, between that enrollment figure and the 174 participants at risk listed for each arm in the adverse-event data. No reconciliation should be assumed from the registry entries.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Efficacy and Safety of Gabapentin/B-complex Versus Pregabalin in Diabetic Peripheral Neuropathy Pain Management — NCT01364298.
- Registry record last updated 2014-02-06; status last verified 2013-12.
- Results first posted 2014-02-06.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed, multicenter, randomized, open-label, parallel-group Phase IV trial comparing gabapentin/B-complex with pregabalin for diabetic peripheral neuropathic pain. Enrollment is listed as 353. The trial start is listed as 2011-04 and primary completion as 2012-07.
The primary outcome is change from baseline in average NPIS score at Day 84 (Week 12), with change defined as baseline minus follow-up and the primary population described as per protocol. NPIS is an 11-point scale ranging from 0, no pain, to 10, the worst possible pain. The registry record does not report the primary outcome estimates or a statistical comparison.
Serious adverse-event counts are listed as 1 among 174 at risk for gabapentin/B-complex and 0 among 174 at risk for pregabalin. Other adverse-event counts are 79 and 93, respectively, with 174 at risk in each group. The record lists cerebrovascular disorder at 0.6% among top serious-event terms; deaths are not reported in the registry record.