Safety and Efficacy of Gabapen for Pediatric (Regulatory Post Marketing Commitment Plan): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Efficacy of Gabapen for Pediatric (Regulatory Post Marketing Commitment Plan) (NCT01441401), a registered phase not stated study. The primary outcome is Number of Participants With Treatment-Related Adverse Events.

2. Clinical Question

3. Trial Design

The registry record identifies this as a completed special investigation of Gabapen for pediatric use, with a regulatory post-marketing commitment plan. Enrollment was 82. The record lists one gabapentin group, described as pediatric participants taking Gabapen tablets and syrup. There is no comparator group listed, and allocation is not stated. The record does not describe randomization or a blinded design, so the results should be read as observations from the listed treatment group rather than as a controlled estimate of treatment effect.

The study start is recorded as 2011-12 and primary completion as 2014-08. Its status is COMPLETED. The primary endpoint timeframe is MAX 104 weeks, but the actual follow-up duration for participants, the treatment duration, and the schedule of safety or efficacy assessments are not reported in the registry record. The stated timeframe should not be taken to mean that every participant was observed for the maximum period.

The stated investigation aims were to understand the frequency of treatment-related adverse events, the frequency of efficacy assessment, treatment-related adverse events not listed in the Japanese Package Insert, and risk factors likely to affect the frequency of treatment-related adverse events. These aims describe the scope of the investigation; the registry record does not provide a detailed protocol or a statistical analysis plan. It also does not report the study setting, recruitment method, or the number of participants who completed follow-up. The sponsor is listed as Pfizer's Upjohn has merged with Mylan to form Viatris Inc.

There are 13 outcome measures and 6 analyses listed in the record. The secondary outcomes include adverse-event and response categories, but the titles alone do not establish which analyses were prespecified, how they were conducted, or whether all enrolled participants contributed to each one. Those details 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

Analysis population for the primary outcome, as defined in the registry: The safety analysis population comprised of participants who had met the inclusion criteria and had taken gabapentin at least once.

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Treatment-Related Adverse Events, measured over MAX 104 weeks.

The primary endpoint is the number of participants with treatment-related adverse events, with a timeframe of MAX 104 weeks. A treatment-related adverse event is defined as an untoward medical occurrence attributed to gabapentin in a participant who received gabapentin. Relatedness was assessed by the investigator and sponsor, identified as Pfizer Japan Inc. This definition makes attribution part of the outcome: the measure is not simply a count of every medical occurrence during observation.

The safety analysis population comprises participants who met the inclusion criteria and took gabapentin at least once. A participant count can communicate how many people experienced an event, while the denominator indicates how many were considered at risk in the analysis. These counts do not, by themselves, show when events occurred, how long they lasted, how many separate events an individual experienced, or how severe every event was.

Safety endpoints of this kind are used in post-marketing investigations to describe events observed during treatment and to examine whether unexpected events or potential risk factors warrant further attention. They do not establish that gabapentin caused every event attributed to it, because attribution is an assessment rather than a randomized causal contrast. The record reports 82 participants at risk in the listed adverse-event group, including 4 with serious adverse events and 25 in the other adverse-event category. An explicit overall result for the primary endpoint is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is expressed as a participant count. This is a binary outcome at the participant level: a person is classified according to whether the defined event occurred during the relevant observation period. A count is useful for describing the observed number of affected participants, but it is most interpretable alongside the number at risk and a clear account of how events and participants were classified. The registry lists 82 participants at risk in the adverse-event group. It does not provide an explicit overall count for the primary treatment-related adverse-event endpoint.

A count of participants with at least one event differs from a count of all event episodes. If one participant has multiple episodes, a participant-level count still represents that person once, whereas an episode count can include each occurrence. The posted serious and other adverse-event figures are presented as numbers of participants. The record does not give event-level totals or details about repeated episodes, so those counts should not be interpreted as the total number of medical occurrences.

In general, a confidence interval describes the range of values compatible with the observed data under a stated statistical method. It communicates sampling uncertainty and is more informative about precision than a point estimate alone. No confidence interval for the primary endpoint is reported in the registry record. A p-value would address a specified statistical test and hypothesis; neither a primary-endpoint p-value nor the corresponding test is reported in the registry record for this record. In the absence of an explicit interval or test, precision and statistical evidence against a defined null hypothesis cannot be evaluated from the listed counts alone.

General statistical context is important for a single-group investigation. A controlled comparison can help separate an outcome observed during treatment from changes that might also occur because of the underlying condition, background care, participant characteristics, or observation practices. Here, no comparator group is listed and allocation is not stated. The recorded counts therefore describe the group under observation, but do not quantify a treatment effect relative to an alternative. Investigator and sponsor assessment of relatedness adds a defined attribution process, but does not create a randomized comparison.

Over-dispersion is a general concern when a model assumes a particular level of variation but the data vary more than that model allows. It can lead to uncertainty estimates that are too narrow if the model is not suitable. That issue is often considered for event counts, especially when people can experience multiple events. The primary measure in this record is a participant count, and the registry entries do not report a model, repeated-event analysis, or a dispersion assessment. There is therefore no basis to state whether over-dispersion was tested or how it was handled.

The registry's sample-size assumptions describe a planning illustration computed from an observed effect, not the design of this investigation. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. The registry entries do not provide a planning result to interpret. More fundamentally, this record lists one treatment group rather than a randomized two-arm comparison. Such an illustration is hypothetical planning information and must not be presented as observed power, as a feature of the original design, or as evidence that the study could detect a particular effect.

General power calculations concern the probability that a specified design and analysis will detect an effect of a specified size under stated assumptions. They depend on the endpoint, allocation, variability or event frequency, significance threshold, and analysis approach. A sample-size illustration based on an observed effect is especially dependent on the reliability of that effect estimate. The registry record does not report a sample-size justification for the investigation, and the planning assumptions do not establish that the study was designed around them.

Outcome titles also do not reveal the analysis method. The record lists 13 outcome measures and 6 analyses, but does not describe model specifications, covariate adjustment, subgroup testing, handling of repeated assessments, or the derivation of response. Those methods are not reported in the registry record. Accordingly, the numerical safety descriptions can be read as descriptive counts, while further inferential interpretations would require methods and results that are not reported.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Gabapentin Tablets/Syrup")
n      <- c(82)
events <- c(5)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Gabapentin Tablets/Syrup  82  5  6.1  2.0  13.7  2.6  13.5  2.7  13.5

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, subgroup analyses, or statistical tests are considered. In general, testing many hypotheses can increase the chance of obtaining at least one apparently notable result by chance. Statistical plans may address this with a prespecified primary outcome, a hierarchy of tests, or an adjustment procedure. The record lists 13 outcome measures and 6 analyses, including multiple safety and efficacy-related topics, but a multiplicity strategy is not reported in the registry record. It is also not reported which analyses, if any, were confirmatory rather than exploratory.

Missing data can affect both the number of participants included in an analysis and the meaning of its results. For example, follow-up may be incomplete, or an outcome may not be assessed for every participant. The registry record does not report the amount or pattern of missing data, withdrawals, losses to follow-up, or methods used to handle missing outcomes. The number who completed follow-up and the extent of outcome-specific denominators are also not reported.

The safety population is defined as participants who met inclusion criteria and took gabapentin at least once. The adverse-event group lists 82 participants at risk. The record does not report additional analysis-population definitions for the response outcomes, or whether efficacy analyses used the same participants as the safety analysis. It also does not report how exclusions or deviations from the intended treatment were handled. These omissions limit assessment of whether each result represents all enrolled participants or a subset selected by treatment exposure, follow-up, or outcome availability.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: bronchitis (2.4%), febrile convulsion (1.2%), humerus fracture (1.2%).

The adverse-event summary lists 82 participants at risk, 4 participants with serious adverse events, and 25 participants in the other adverse-event category. The counts refer to participants, not necessarily to the total number of event episodes. The registry record does not explain the exact classification represented by the other category in the registry record for this investigation. It is therefore safest to preserve the category label rather than assume a more specific definition.

The serious terms listed are Bronchitis, 2.4%; Febrile convulsion, 1.2%; and Humerus fracture, 1.2%. The percentages are reproduced as reported. The record does not specify the number of separate events for each term, whether an individual could contribute to multiple terms, or the method used to calculate each percentage. The listed terms do not establish that gabapentin caused them; the endpoint definition says relatedness was assessed by the investigator and sponsor, while the serious-term list is a descriptive record.

Serious adverse events and treatment-related adverse events are not interchangeable concepts. Seriousness is a classification of an event, whereas treatment relatedness is an attribution to gabapentin. The registry record does not provide an explicit overall primary treatment-related-event count alongside the serious-event count. These figures should not be added together, treated as mutually exclusive groups, or used to infer an unreported total.

13. What the Result Does, and Does Not, Mean

The results support a limited descriptive reading: the registry records adverse events among participants taking gabapentin, including 4 participants with serious adverse events and 25 participants in the other adverse-event category among 82 at risk. It also lists serious-event terms and their reported percentages. These are observations from the group described in this record. They offer a summary of what was recorded, not a controlled estimate of the risk attributable to gabapentin.

The results do not establish whether gabapentin increases or decreases adverse-event frequency relative to another treatment, because no comparator is listed and allocation is not stated. They do not show that every listed event was caused by gabapentin. The relatedness definition describes investigator and sponsor assessment; it does not remove the uncertainty that comes with attribution in an uncontrolled investigation. Nor do the counts describe the timing, duration, recurrence, or outcome of each event.

The primary endpoint is the number of participants with treatment-related adverse events, but an explicit overall result for that endpoint is not reported in the registry record. The serious and other category counts are not a replacement for a separately reported primary result. Numerical efficacy findings are also not reported, despite secondary outcome titles relating to treatment response and assessment by baseline characteristics or treatment period. The record therefore does not support a conclusion about the magnitude of any response or how it varied across those groups.

Interpretation is constrained by the information recorded about follow-up, participant characteristics, missing data, and analysis methods. The stated maximum timeframe does not indicate that every participant was observed for that duration. Without fuller denominators, precision estimates, and a defined comparative analysis, the counts cannot show how stable they might be in another population or setting. They are best understood as registry-level descriptive information from a post-marketing investigation, with important details not reported in the registry record.

14. Why This Trial Matters Statistically

This investigation matters statistically because it illustrates the distinction between describing events after treatment exposure and estimating a comparative treatment effect. Post-marketing safety work can collect information about treatment-related events and unexpected events in a population of interest. A single-group count can document what was recorded, but interpretation depends on clear event definitions, denominators, follow-up, and assessment of relatedness. The registry defines treatment-related events and identifies who belongs to the safety population, while leaving several details of the analysis unreported.

The record also demonstrates why counts need context. The serious-event count, the other adverse-event count, the listed serious terms, and the primary endpoint are related safety descriptions but are not necessarily the same measure. Separating participant counts from event episodes, seriousness from relatedness, and a subgroup term from an overall endpoint prevents unsupported arithmetic or causal interpretation. The absence of an explicit overall primary result is particularly important when the study's stated central aim concerns treatment-related adverse events.

The efficacy-related outcome titles create another useful distinction: a listed outcome is not the same as a reported result. The secondary outcomes refer to response across baseline severity, seizure frequency, concomitant antiepileptic drug count, and treatment period, but numerical efficacy findings are not reported in the registry record. Naming those analyses does not establish the size, precision, or consistency of an observed response.

Finally, planning calculations should be separated from design and results. The stated sample-size illustration uses assumptions for a hypothetical two-arm planning exercise, whereas this investigation lists a single treatment group. It cannot be treated as observed power or as evidence of the original design's adequacy. This distinction helps keep descriptive post-marketing findings, hypothetical planning, and causal comparisons conceptually separate.

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.

The most important limitation is the absence of a listed comparator group. Allocation is not stated, so the record does not support a controlled estimate of treatment effect or a direct comparison of event frequency under different treatment strategies. The setting and recruitment approach are not reported in the registry record, limiting assessment of how participants may represent a wider pediatric population.

The reported safety information is incomplete for detailed interpretation. The record lists 82 participants at risk, 4 with serious adverse events, and 25 in the other adverse-event category, but does not define the other category in the registry record. An explicit overall count for the primary treatment-related adverse-event endpoint is not reported. Event timing, duration, recurrence, outcome, and event-level totals are also not reported. The percentages attached to serious terms are not accompanied by a calculation method or term-specific participant counts.

Follow-up details are limited. MAX 104 weeks is the primary endpoint timeframe, but actual observation duration, assessment schedule, treatment duration, and follow-up completion are not reported in the registry record. Missing data, withdrawals, outcome-specific denominators, and methods for handling incomplete observations are likewise not reported. The record does not provide detailed baseline characteristics, including the distributions of seizure severity, seizure frequency, or concomitant antiepileptic drugs.

Statistical interpretation is further limited because the analysis plan, uncertainty estimates, and multiplicity handling are not reported. The efficacy outcome titles have no numerical results in the registry record for this record. These gaps mean that subgroup patterns, precision, and the robustness of any findings cannot be assessed from the registry record alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety and Efficacy of Gabapen for Pediatric (Regulatory Post Marketing Commitment Plan) — NCT01441401.
• Registry record last updated 2021-02-03; status last verified 2016-08.
• Results first posted 2016-10-06.
• 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.

19. Record Summary

NCT01441401 is a completed special investigation of gabapentin for pediatric participants with partial epilepsies, described as a regulatory post-marketing commitment plan. Enrollment was 82. The listed intervention was gabapentin, with participants described as taking Gabapen tablets and syrup. No comparator group is listed, and allocation is not stated. The study start is 2011-12 and primary completion is 2014-08.

The primary endpoint was the number of participants with treatment-related adverse events over a maximum timeframe of 104 weeks. The adverse-event summary lists 82 participants at risk, 4 with serious adverse events, and 25 in the other adverse-event category. Serious terms include Bronchitis, 2.4%; Febrile convulsion, 1.2%; and Humerus fracture, 1.2%. An explicit overall primary-endpoint count and numerical efficacy results are not reported in the registry record. Details on missing data, follow-up completeness, and statistical analysis methods are also not reported.