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 Gabapentin to Improve Patient Tolerance in Endoscopic Retrograde Cholangiopancreatography (ERCP) (NCT01143766), a randomized na study. The primary outcome is Dosing Requirements.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01143766 |
| Phase | NA |
| Condition | Conscious Sedation |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 56 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Indiana University |
| Results posted | Yes |
2. Clinical Question
Population
Participants undergoing endoscopic retrograde cholangiopancreatography (ERCP) in a trial concerned with conscious sedation. The registry record reports enrollment of 56 participants. It does not provide further eligibility details or a description of the enrolled participants.
Intervention
A single oral dose of gabapentin, 900mg, one hour before the procedure. Participants then received sedation in a standard fashion at the time of ERCP.
Comparator
Standard sedation, described as a combination of an opiate and a benzodiazepine. The registry identifies this as the current standard of care for the study.
Primary question
Whether premedication with gabapentin affects intra- and post-procedure narcotic or sedative requirements, assessed through the total dose of meperidine at discharge after the procedure. The posted measure is the median total dose, with an inter-quartile range.
The clinical question is therefore about medication requirements during and after ERCP, not a direct measure of procedure success. The registry summary also describes pain, patient satisfaction, and opiate requirements as reasons for studying gabapentin, but satisfaction is not among the listed secondary outcomes. The listed secondary measures include sedation-related adverse events and median pain, anxiety, and nausea scores at discharge.
The comparison is between randomized groups, but the registry record does not report a numerical estimate of the difference between groups, its uncertainty, or a hypothesis-test result. The posted medians can describe the observed dose distributions; they do not alone establish whether the groups differ beyond the trial participants. Nor do the endpoint results by themselves answer every question about tolerability, because those questions involve other outcomes as well as the primary measure.
3. Trial Design
The registry classifies this study as a randomized, parallel-group trial with triple masking. It reports that the trial was completed and lists enrollment of 56 participants. The phase is listed as NA. The sponsor is Indiana University. The recorded start is 2010-04, and primary completion is recorded as 2011-12.
Participants were assigned to standard sedation or to gabapentin followed by standard sedation at the procedure. The standard-sedation arm is described as receiving a combination opiate and benzodiazepine. In the gabapentin arm, participants were to receive a single 900mg oral dose one hour before ERCP and then be sedated in a standard fashion. This design compares adding a pre-procedure dose to the standard approach with the standard approach alone; it is not a comparison of gabapentin against no sedation.
Random allocation is intended to make the groups comparable on average, while parallel-group assignment means participants remain in their assigned group rather than crossing between treatments. Masking can reduce the influence of treatment knowledge on conduct or assessment, but the registry record does not identify which parties were included in triple masking or how masking was maintained. It also does not report the randomization procedure, allocation concealment, or protocol details beyond the arm descriptions.
The registry reports 25 participants in the standard-sedation arm and 31 in the gabapentin arm for the primary result. The record does not state whether these are all randomized participants, participants with available endpoint data, or another analysis population. A sample-size justification, stopping rules, and interim-analysis plan are not reported in the registry record.
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 | Standard Sedation | Gapabentin |
|---|---|---|
| STARTED | 25 | 31 |
| COMPLETED | 25 | 31 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: TOTAL DOSE OF MEPERIDINE
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 | Standard Sedation | Gapabentin | Total |
|---|---|---|---|---|
| Participants analysed | 25 | 31 | 56 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 21 | 27 | 48 |
| Age, Categorical: >=65 years | Participants | 4 | 4 | 8 |
| Age, Continuous | years | 49.1 (SD 16.6) | 48.1 (SD 12.8) | 48.6 (SD 14.5) |
| Sex: Female, Male: Female | Participants | 15 | 19 | 34 |
| Sex: Female, Male: Male | Participants | 10 | 12 | 22 |
| Region of Enrollment: United States | participants | 25 | 31 | 56 |
6. Primary Endpoint
The registry lists the primary outcome as Dosing Requirements, measured over At time of discharge post-procedure.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | TOTAL DOSE OF MEPERIDINE, mg |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the total dose of meperidine, measured in milligrams at discharge after the procedure. It is reported as a median with an inter-quartile range. This endpoint is intended to quantify narcotic requirements associated with the ERCP episode. In the context of the study question, a dose measure can indicate how much meperidine participants received during the intra- and post-procedure period, rather than relying only on a subjective rating of symptoms.
The posted median is 100.0 mg for standard sedation, with an inter-quartile range of 88.0 to 125.0 mg. For gabapentin, the median is 100.0 mg, with an inter-quartile range of 100.0 to 150.0 mg. The IQR describes the middle half of the observed values and is not a confidence interval for the median or for a difference between groups. The registry does not report the underlying participant-level doses or a formal between-group estimate.
Meperidine dose is only one aspect of sedation and tolerability. The registry lists other outcomes, including pain, anxiety, nausea, and sedation-related adverse events. The posted primary measure does not by itself establish how participants felt, how sedation was judged, or whether other clinical outcomes differed.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The principal posted finding is that the median total meperidine dose at discharge was 100.0 mg in each group. The distributional summaries are not identical: the standard-sedation group has an inter-quartile range of 88.0 to 125.0 mg, while the gabapentin group has an inter-quartile range of 100.0 to 150.0 mg. These are descriptive summaries of the observed participants. They do not establish the size or precision of a group contrast.
The registry record does not report a comparative estimate, confidence interval, or p-value for the primary endpoint. Without those results, the precision of any contrast and the compatibility of the observations with a range of possible effects cannot be assessed from the registry posting. The same median in both groups is not, by itself, proof that the underlying distributions are equivalent. Conversely, different IQR limits do not by themselves establish a meaningful or statistically reliable difference.
The endpoint is a countable medication dose, but the posted result is a median rather than a mean. A median describes the center of an ordered distribution and is less sensitive than a mean to unusually high or low observations. The IQR communicates spread across the central portion of that distribution. Neither statistic gives a complete account of the distribution, and neither shows whether individual values overlap or how uncertainty in the group summaries compares.
The primary result should also be read alongside the trial's sample sizes: 25 participants are listed for standard sedation and 31 for gabapentin. The registry does not say whether every enrolled participant contributed an endpoint value, nor does it provide a missing-data account or the analysis population. These omissions matter when judging how representative the reported summaries are of the randomized groups.
Four secondary outcomes are listed: participants with sedation-related adverse events and median pain, anxiety, and nausea scores at discharge. Their numerical results are not reported in the registry record. The registry reports 0 participants with serious adverse events in each group, and reports other adverse events in 3 participants receiving standard sedation and 4 receiving gabapentin. Those counts are descriptive safety information, not a comparative safety analysis.
Overall, the record supports a narrow interpretation: it posts group-level medians and IQRs for meperidine dose and adverse-event counts, but does not post inferential results for the primary or secondary outcomes. The findings should not be extended to outcomes or populations that the registry does not describe.
9. Statistical Methods Explained
Statistical interpretation depends on distinguishing descriptive summaries from estimates of treatment contrasts. The registry posts a median and inter-quartile range for each arm's total meperidine dose. These statistics describe the observed dose distributions; they are not themselves a test of whether assignment to the groups was associated with a difference. The registry record does not report a formal comparison or an interval estimate for the primary endpoint.
What does the median describe?
In general, the median is the center of an ordered set of observations: half the observations are at or below it and half are at or above it, subject to ties and the convention used for an even number of observations. It is useful when a distribution may be skewed or contain extreme values. A median does not describe the average dose, and it does not reveal the full shape of the distribution.
The IQR is, in general, the span between the lower and upper quartiles. It describes the spread of the central half of observations. The reported IQRs are 88.0 to 125.0 mg for standard sedation and 100.0 to 150.0 mg for gabapentin. An IQR is a descriptive range, not a confidence interval. It does not directly quantify uncertainty in the median or in a comparison of medians.
What would a comparative estimate add?
In general, an effect estimate states the contrast being assessed, such as a difference between group summaries, while a confidence interval expresses the estimate's statistical uncertainty under the method's assumptions. A hypothesis test addresses compatibility with a specified null hypothesis, but a p-value alone does not give the magnitude or clinical meaning of a contrast. For this trial, the registry record does not report an effect estimate, confidence interval, or p-value for the primary endpoint, so none can be interpreted from the posted summary statistics.
Randomization supports causal comparison when allocation is implemented appropriately and outcomes are analyzed in a way that preserves the randomized comparison. It does not ensure that every group characteristic is numerically identical, especially in a trial of this size. The registry identifies randomized allocation but does not report the method used to generate or conceal assignments, the prespecified analysis population, or the primary analysis method. Those details are not reported in the registry record.
How should the sample-size illustration be understood?
The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The illustration considers detecting a stated fraction of the observed effect. In general, such calculations estimate how many participants per arm would be required under specified assumptions to target a chosen power. They are planning illustrations, not evidence that the trial had that power and not a measure of the probability that its findings are correct.
The record does not report the trial's own sample-size justification. It also does not provide the resulting planning counts in the registry record for this analysis. The illustration's assumptions should therefore not be mistaken for the original protocol's rationale. Calculations based on an observed effect can be sensitive to the particular estimate used, and they do not substitute for an analysis of the observed data. Sample sizes in such illustrations are prospective planning quantities, not participants observed in this trial.
More generally, a normal approximation relies on conditions that make the chosen statistical procedure reasonable. For count or continuous outcomes with strongly skewed distributions, a method aligned with the data structure may be preferable. Over-dispersion, in general, means variability exceeds what a model's assumed distribution would predict; ignoring it can make uncertainty appear too small. The registry record does not report enough detail to determine what distributional assumptions or inferential methods were used for the endpoint.
What can the posted safety counts establish?
Counts of participants with events are descriptive. A comparative safety assessment would ordinarily need a clearly specified event definition, the population under observation, follow-up duration, and an estimate with appropriate uncertainty. The registry reports serious-event counts and other-event counts by group, but does not report those additional details or a formal comparison. A zero count in a group means no such event was recorded among the listed participants for that category; it does not establish that the underlying event risk is zero.
The registry lists a total of five outcome measures, including the primary outcome and four secondary outcomes. In general, testing multiple outcomes raises multiplicity concerns: conducting several tests can increase the chance that at least one result appears notable by chance if no adjustment or prespecified hierarchy is used. The registry record does not report a multiplicity strategy, so it is not possible to determine whether any adjustment was planned or performed.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome, dosing requirements measured by total meperidine dose at discharge, and four secondary outcomes: sedation-related adverse events, pain score at discharge, anxiety score at discharge, and nausea score at discharge. The record does not report a hierarchy among the secondary outcomes or a method for adjusting for multiple comparisons. In general, when several outcomes are examined, the chance of a nominally notable result arising by chance can increase; prespecified priorities or multiplicity adjustments can address that issue. Whether either approach was used is not reported in the registry record.
The posted primary outcome contains group medians and IQRs, but the registry does not report a comparative analysis. Numerical results for the four secondary outcomes are not reported in the registry record. The record lists zero analyses, which means no analysis results are listed in the registry entry; it does not establish that no analyses were conducted outside the entry.
Missing-data information is not reported in the registry record. It does not state how many participants had usable data for each outcome, whether any observations were missing, or how missing values were handled. The primary arm counts are 25 and 31, but the record does not explain whether those counts represent randomized participants or participants with outcome data.
The analysis population is likewise not reported in the registry record. It is not stated whether results use all randomized participants, participants treated as assigned, or another population. These details affect how closely an analysis reflects the randomized comparison and how readers should understand the reported summaries. Interim analyses, stopping rules, and the statistical analysis plan are not reported in the registry record.
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 |
|---|---|---|---|
| Standard Sedation | 0 | 25 | 0.0% |
| Gapabentin | 0 | 31 | 0.0% |
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 |
|---|---|
| Standard Sedation | 3 of 25 |
| Gapabentin | 4 of 31 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Standard Sedation | Gapabentin |
|---|---|---|---|
| Hypoxemia or apnea | Respiratory, thoracic and mediastinal disorders | 3 of 25 | 2 of 31 |
| Dizziness | Nervous system disorders | 0 of 25 | 2 of 31 |
The registry reports 0 participants with serious adverse events in the standard-sedation arm, with 25 at risk, and 0 in the gabapentin arm, with 31 at risk. It also reports other adverse events in 3 participants in the standard-sedation group and 4 participants in the gabapentin group. These counts are descriptive; the registry does not provide a formal comparison, uncertainty estimates, or additional detail about the event definitions.
A zero observed count should not be read as proof that an event cannot occur or that the underlying risk is zero. It means that no serious adverse event was recorded for the listed participants in that arm in the posted results. The registry record does not report a separate death count, and it does not describe the duration or completeness of safety follow-up. Death counts are therefore not reported in the registry record.
The four other adverse events reported across the two groups are not equivalent to a complete account of every possible harm. The record also lists sedation-related adverse events as a secondary outcome, but does not provide its numerical results. The serious-event counts and other-event counts should be interpreted as limited safety summaries, not as a definitive comparison of safety between groups.
12. What the Result Does, and Does Not, Mean
The posted primary results describe observed meperidine dosing in this randomized trial. The median total dose at discharge was 100.0 mg in both groups. The accompanying IQRs differ, with 88.0 to 125.0 mg for standard sedation and 100.0 to 150.0 mg for gabapentin. These summaries are informative about the center and spread of the observed doses, but they do not provide a statistical estimate of the group contrast.
Because there is no reported confidence interval or p-value for the primary endpoint, the registry entry does not establish the precision of a comparison or whether the observed summaries are compatible with a range of treatment effects. Matching medians do not prove equivalence, and differing IQRs do not establish a treatment effect. Equivalence or non-inferiority conclusions would require an appropriate design and prespecified analysis, neither of which is reported in the registry record.
The study question also involves tolerability, and the primary endpoint captures medication requirement rather than all aspects of tolerance. The secondary outcomes include pain, anxiety, nausea, and sedation-related adverse events, but their results are not reported in the registry record. The available adverse-event counts are limited summaries and do not answer every safety question.
The trial enrolled 56 participants, and the primary results list 25 participants for standard sedation and 31 for gabapentin. The registry does not clarify the relationship between these counts and the analysis population or describe missing endpoint data. As a result, the scope of the summaries cannot be fully assessed from the entry.
These results should be understood as a record of the posted outcome data, not as medical advice or as a complete account of the evidence on gabapentin for ERCP. They do not establish that gabapentin improves or worsens patient tolerance, changes sedation requirements, or alters safety. The registry record does not report the comparative analyses needed to support those broader conclusions.
13. Why This Trial Matters Statistically
This trial raises a useful statistical question because its primary endpoint is a medication dose summarized by medians and IQRs, while its clinical objective includes patient tolerance. The distinction matters: a concise numerical summary can describe the observed dose distribution, but it cannot stand in for a formal comparison or for patient-reported outcomes. The posted medians are the same, while the IQRs differ; neither feature alone resolves the inferential question.
The randomized parallel design makes a group comparison conceptually relevant, but interpretation depends on more than the allocation label. Readers also need to know which participants contributed data, how missing outcomes were handled, what analysis was prespecified, and how uncertainty was quantified. Those details are not reported in the registry record. Their absence limits the conclusions that can be drawn from the posted summaries, even though the group-level values themselves are available.
The record also illustrates why safety counts need context. Zero serious adverse events in each group is a clear description of what was posted, but it is not an estimate that establishes zero risk. Event definitions, follow-up, and uncertainty are needed to interpret sparse counts. Similarly, the listed secondary outcomes could address dimensions of tolerability beyond dose, but their numerical results are not reported.
Finally, the planning illustration is distinct from the trial's original design justification and from observed evidence. It uses stated assumptions and an observed effect for planning purposes; it does not reveal the trial's achieved power or replace confidence intervals and estimates. Keeping descriptive results, inferential analyses, safety summaries, and planning calculations separate helps prevent stronger conclusions than the registry entry supports.
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 registry record offers limited detail for evaluating the trial's methods. It identifies randomized allocation, triple masking, and a parallel model, but does not describe the randomization sequence, allocation concealment, or the parties who were masked. It does not report eligibility criteria or detailed characteristics of the enrolled participants. These omissions restrict assessment of how the trial was conducted and to whom its results may apply.
The primary endpoint is reported with group medians and IQRs, but no comparative effect estimate, confidence interval, or p-value is reported. The posted figures therefore do not show the uncertainty around a group contrast. The record also does not report participant-level data, a distributional description beyond median and IQR, or the method used to analyze the endpoint.
Although four secondary outcomes are listed, their numerical results are not reported in the registry record. A multiplicity approach is not reported. The record does not state the analysis population, whether outcome data were missing, or how any missing data were handled. It also does not report interim analyses or a statistical analysis plan. These are limitations of what can be evaluated from the registry entry, not evidence that a particular procedure was or was not used.
Safety reporting is also limited: serious and other adverse-event counts are posted, but event definitions, follow-up details, and formal comparisons are not. Death counts are not reported in the registry record. The sample-size illustration is described as based on the observed effect and specified assumptions, but the trial's own sample-size justification is not reported in the registry record. Together, these gaps mean the posted information supports descriptive reading more readily than a comprehensive assessment of efficacy, precision, or safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Gabapentin to Improve Patient Tolerance in Endoscopic Retrograde Cholangiopancreatography (ERCP) — NCT01143766.
- Registry record last updated 2023-09-28; status last verified 2023-09.
- Results first posted 2012-12-05.
- 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 randomized, triple-masked, parallel-group trial of gabapentin premedication before ERCP. Enrollment was 56. The gabapentin arm received a single 900mg oral dose one hour before the procedure, followed by standard sedation; the comparator received standard sedation with an opiate and benzodiazepine.
The primary outcome was total meperidine dose at discharge, summarized as a median and IQR. The median was 100.0 mg in both groups; the IQR was 88.0 to 125.0 mg for standard sedation and 100.0 to 150.0 mg for gabapentin. The registry does not report a formal comparative analysis. Four secondary outcomes are listed, but their numerical results are not reported in the registry record. Serious adverse events were reported in 0 participants in each group, while other adverse events were reported in 3 and 4 participants, respectively.