Varenicline (Chantix™) for the Treatment of Alcohol Dependence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Varenicline (Chantix™) for the Treatment of Alcohol Dependence (NCT00705523), a randomized phase 2 study. The primary outcome is Rate of Heavy Drinking Days Per Week..

2. Clinical Question

The registry describes a randomized, double-blind pilot trial and identifies varenicline as the experimental treatment. The central outcome is a weekly rate, not simply whether a participant ever had a heavy-drinking day. The posted arm summaries give a median rate of 0.89 for varenicline and 1.21 for placebo. The registry also reports a sponsor analysis with p = 0.10, but it does not provide a comparison estimate or confidence interval for that analysis.

Those details frame a comparison, but they do not establish how precisely the groups differ or whether the observed values represent a broader population. The analysis population, eligibility criteria, and missing-data approach are not reported in the registry record. The trial is identified as a pilot, and the record does not report a sample-size justification or a detailed statistical analysis plan. The secondary endpoint provides another outcome measure, but it should be interpreted as supporting context rather than as a substitute for an incomplete primary comparison.

3. Trial Design

This was a completed Phase II, randomized, quadruple-masked, parallel-group pilot trial sponsored by the University of Pennsylvania. The registry lists enrollment of 40 and the two interventions as varenicline and placebo. The posted arm summaries include 19 participants for varenicline and 21 for placebo. The record identifies the study as randomized and quadruple-masked; it does not describe the precise allocation procedure or identify the roles covered by the masking label.

The study began in 2008-06, had primary completion in 2010-03, and is marked completed. The primary outcome timeframe was 12 weeks of treatment and one month of follow-up. The secondary Addiction Severity Index alcohol composite score was assessed at the end of 12 weeks of treatment, with a follow-up one month after treatment. Additional visit schedules and the timing of individual measurements are not reported in the registry record.

The record calls the trial a pilot and lists the primary outcome as a median rate of heavy drinking days per week, with standard deviation as the dispersion measure. The arm descriptions are blank. Dose, treatment adherence procedures, treatment duration details beyond the stated outcome timeframe, and study withdrawal rules are not reported in the registry record. The registry also does not report how the planned enrollment was chosen, whether enrollment targets changed, or how participants were assigned to the reported analysis populations.

The parallel design means that the two treatment groups are compared as separate arms rather than as a crossover sequence. Randomization is intended, in general, to support a fair comparison by distributing measured and unmeasured participant characteristics across groups, though the record does not provide enough detail to assess implementation. Masking can reduce the influence of expectations on participant reporting and study conduct; the registry’s quadruple-masking label is recorded, but its operational details are not. These design features describe the intended structure, not proof that bias was absent.

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

Reasons for not completing this period:

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 Rate of Heavy Drinking Days Per Week., measured over 12 weeks of treatment and one month follow-up.

The primary endpoint is the rate of heavy drinking days per week over 12 weeks of treatment and one month of follow-up. A heavy drinking day was defined as five drinks per day for men and four drinks per day for women. The outcome was determined from participant self-report using the time-line follow-back (TLFB) method. The registry describes the endpoint using a median and standard deviation.

A weekly rate expresses drinking days relative to time observed, which can summarize frequency rather than only recording whether any heavy drinking occurred. The TLFB is a retrospective self-report approach for recording drinking over time. In general, such measurement can capture day-to-day patterns, but it depends on participants recalling and reporting their behavior. The registry does not report the specific recall window, verification procedures, or how periods without complete self-report were handled.

The endpoint is relevant to the stated study purpose because it quantifies the frequency of days meeting the trial’s heavy-drinking definition. The sex-specific drink thresholds are part of the recorded definition and should be kept in view when interpreting the outcome. The registry gives arm medians of 0.89 for varenicline and 1.21 for placebo, with standard deviations of 0.18 and 0.31, respectively. These summaries alone do not provide a complete inferential comparison: the posted primary analysis does not include an effect estimate or confidence interval, and the registry notes that a two-arm comparison was not estimable for this median endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary endpoint as a median rate of heavy drinking days per week and lists standard deviation as its dispersion measure. The reported sponsor method is logistic regression. The record does not explain the model’s outcome coding, covariates, or estimation details. Those omissions matter because an analysis method must be interpreted in relation to how the outcome was represented and which observations were included.

What does a median describe?

In general, the median is the central value when observations are ordered: half of the observed values fall at or below it and half at or above it, subject to ties. It is often used when a distribution is skewed or contains unusually large values. A standard deviation, by contrast, describes spread around a mean under its usual interpretation. Reporting a median together with a standard deviation does not make the endpoint a mean-based outcome, and the registry does not explain why this particular combination was selected.

The primary summaries are medians of 0.89 for varenicline and 1.21 for placebo. The standard deviations are 0.18 and 0.31. These summaries indicate what was posted for each arm, but they do not furnish a standard error or confidence interval for the difference between medians. A valid uncertainty calculation for a median comparison generally requires information about the distribution or a suitable model, beyond these arm summaries. The registry explicitly notes that the two-arm comparison was missing or not estimable for this endpoint, so a recalculated primary contrast is not available.

What does the sponsor’s p-value convey?

The primary reported analysis is described as logistic regression, with p = 0.10. In general, logistic regression models the probability of a binary outcome as a function of predictor variables. The registry does not report the binary outcome used, its threshold, the covariates in the model, or the coefficient and uncertainty estimate. It is therefore not possible to translate the reported p-value into a size or direction of the modeled effect from the registry record alone. The result can be reported faithfully as the sponsor’s analysis, but its model-specific interpretation remains constrained by the missing details.

A p-value measures compatibility between data and a null model under stated statistical assumptions. It does not quantify the probability that the null hypothesis is true. Nor does it tell readers whether an estimated difference is large, small, or precise. An effect estimate paired with a confidence interval would ordinarily help communicate magnitude and uncertainty, but neither is reported for the primary comparison.

How was the secondary comparison recalculated?

The secondary endpoint is a continuous Addiction Severity Index alcohol composite score. The registry reports means and standard deviations for both groups. The recalculated mean difference uses the posted group summaries, with varenicline expressed relative to placebo. This is an unadjusted comparison: it does not incorporate covariates or any other adjustment not present in the posted summary statistics. The recalculated estimate is -0.17, its confidence interval excludes zero, and its unadjusted p-value is 0.012.

In general, an unadjusted mean difference describes the difference between group averages without accounting for other variables. Its confidence interval reflects sampling uncertainty under the calculation’s assumptions. The recalculation relies on the posted group means, standard deviations, and arm sizes. It is not a reproduction of a sponsor model, because the registry lists no sponsor-reported analysis for this secondary endpoint. It also cannot address missing-data procedures, departures from the intended analysis population, or adjustments that may have been made but are not reported in the registry record.

What do the planning illustrations mean?

The planning illustrations use the observed secondary effect as a reference and consider planning for 100%, 75%, and 50% of that observed effect. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The illustrations give participants per arm for 80% power and for 90% power. They are prospective planning examples based on an observed effect, not the trial’s original design justification and not a measure of the trial’s observed power.

In general, a planning calculation asks how many participants might be needed under specified assumptions to detect a chosen effect with a target probability of a statistically significant result. Smaller effects generally require larger samples under otherwise unchanged assumptions. These illustrations depend on the observed estimate, which may itself be unstable in a pilot trial, and on the stated statistical assumptions. They do not establish that the original trial was designed with those assumptions. The registry does not report the original sample-size rationale.

For this secondary endpoint, the planning illustrations list 26 participants per arm for 80% power and 35 for 90% when planning for 100% of the observed effect; 46 and 61 when planning for 75%; and 102 and 137 when planning for 50%. These figures are planning targets per arm, not observed enrollment counts and not evidence that the trial had a particular probability of detecting an effect. They should be read as conditional examples, not as retrospective validation.

Why does multiplicity matter?

When several outcomes or analyses are examined, the chance of at least one apparently notable result can increase. In general, multiplicity procedures address that issue by controlling error rates or by distinguishing planned primary tests from exploratory analyses. The registry lists two outcome measures and one analysis for the primary endpoint, and it posts one secondary outcome. It does not report a multiplicity strategy or specify whether analyses were prespecified in a detailed analysis plan. The unadjusted secondary p-value therefore should not be treated as though it necessarily accounts for all outcomes or analyses considered during the study.

The registry also does not report the analysis population, missing-data method, interim analyses, or detailed model specifications. Those details can affect estimates and their uncertainty. The reported quantities remain interpretable as posted summaries and analyses, but a fuller assessment of the statistical methods would require information absent from the registry record.

10. Analyses Reported by the Sponsor

The sponsor’s primary analysis is reported as logistic regression with p = 0.10. The registry does not provide an effect estimate or confidence interval for that analysis, nor does it describe the model outcome, covariates, or analysis population. The posted primary arm summaries are medians and standard deviations, but the record states that values were missing or not estimable for a two-arm comparison of the median endpoint. A recalculated primary comparison is therefore not available from the posted summaries.

The sponsor’s p-value should be kept distinct from the secondary recalculation. The latter is an unadjusted calculation from the posted means and standard deviations for the Addiction Severity Index alcohol composite score; no sponsor analysis is reported for that outcome. It does not reproduce or supersede the primary logistic regression result. The registry does not flag a discrepancy between sponsor results and recalculations, but the different endpoints and methods also mean the secondary calculation cannot fill in missing primary effect information.

In general, the sponsor’s analysis is the relevant report of the trial’s planned or conducted primary inference when its details are available. Here, the registry record supplies only a method label and p-value, so the conclusion that can be drawn from the sponsor result is limited to that reported statistic. The descriptive arm medians give context, but they do not establish an adjusted or modeled treatment contrast.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, including the primary heavy-drinking-days endpoint and the secondary Addiction Severity Index alcohol composite score. It reports one primary analysis and no sponsor analysis for the secondary outcome. A multiplicity adjustment, hierarchy among secondary outcomes, or prespecified strategy for interpreting several tests is not reported in the registry record. In general, multiplicity matters because examining several outcomes or analyses can raise the chance of seeing a nominally notable result even when effects are absent. The unadjusted secondary p-value should therefore be interpreted with that limitation in mind.

The record does not report how missing observations were handled, whether participants were analyzed according to randomized assignment, or which analysis population was used for either outcome. It also does not describe whether participants with incomplete follow-up contributed to the primary endpoint, or how incomplete TLFB reports were treated. These details can influence both the estimates and their precision. The registry’s statement that the primary two-arm comparison was missing or not estimable does not explain whether the obstacle was missing data, the endpoint’s analysis method, or another reason.

Interim analyses and any stopping rules are not reported in the registry record. A detailed statistical analysis plan, including model specifications and covariate adjustments, is also not reported. These omissions do not show that such procedures were absent; they mean that the registry entry does not establish whether they were used. Likewise, although the trial is described as randomized and quadruple-masked, the record does not describe allocation concealment or how masking was maintained.

These gaps limit assessment of bias, analytic flexibility, and the robustness of the findings. The posted estimates and sponsor p-value can be described, but their interpretation cannot be fully audited without information on analysis populations, missing-data handling, prespecification, and multiplicity. The secondary recalculation is explicitly unadjusted and should not be mistaken for an analysis that resolves these uncertainties.

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 non-serious adverse event terms

The registry reports no serious adverse events among the 19 participants at risk in the varenicline group and none among the 21 participants at risk in the placebo group. It reports other adverse events affecting 17 of 19 participants in the varenicline group and 19 of 21 in the placebo group. No serious adverse event terms are listed. Death counts are not reported in the registry record.

These figures describe the adverse-event counts posted for this trial; they do not identify event types, timing, duration, or severity for the non-serious events. The record does not explain how events were collected or whether the listed counts represent participants with at least one event under a specified observation window. The study’s enrollment was 40, and the safety summaries cover the arm sizes stated above, but the registry does not provide additional detail about safety analysis populations or missing safety follow-up.

In general, the absence of reported serious events in a small trial does not rule out uncommon harms, and counts from one study do not establish comparative safety in other populations or settings. These data should be read as what the registry reports, not as a complete safety profile or a treatment recommendation.

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

The registry describes a randomized Phase II pilot comparison of varenicline and placebo for alcohol dependence. For the primary outcome, the posted medians are 0.89 and 1.21 heavy drinking days per week, respectively. The sponsor reports a logistic regression p-value of 0.10. Because no primary comparison estimate or confidence interval is reported, the magnitude and precision of the sponsor’s modeled result cannot be assessed from the registry record.

The secondary alcohol composite score has lower posted mean values in the varenicline arm, and an unadjusted summary-based recalculation gives a mean difference of -0.17 with an interval excluding zero. This is a secondary result without a sponsor-reported analysis or a reported multiplicity strategy. It offers additional descriptive context but does not resolve the missing primary comparison or establish a confirmatory effect.

In general, statistical evidence is strongest when an estimate, its uncertainty, the analysis method, and the handling of missing data are all clear and aligned with a prespecified question. Here, several of those details are not reported. The p-value alone cannot show the size or practical importance of a difference, while arm summaries alone cannot establish a reliable treatment contrast. The pilot designation and enrollment further make precision and generalizability important considerations, although the registry does not report the intended sample-size rationale.

The record does not establish that the observed differences would persist in a larger or different study, nor does it describe how results varied across participant subgroups. It reports no detailed information about adherence, dose, eligibility criteria, or follow-up completeness. The posted findings should therefore be understood as outcome summaries and analyses from this completed study, not as proof about treatment effects in other settings. They do not support medical advice.

14. Why This Trial Matters Statistically

This trial illustrates a distinction that is central to clinical statistics: descriptive group summaries and an inferential comparison answer related but different questions. The registry provides primary arm medians and standard deviations, but the two-arm median comparison is missing or not estimable. The sponsor’s analysis supplies a p-value but not an effect estimate or confidence interval. Readers can see the direction of the arm summaries, yet cannot fully assess the modeled magnitude or precision of the primary comparison.

The secondary endpoint shows why calculations from posted summaries can be useful but must be labeled carefully. An unadjusted recalculation offers an estimate and interval for the alcohol composite score, while remaining distinct from the sponsor’s primary analysis. It does not account for unreported model choices, missingness, or multiplicity. Keeping these analyses separate prevents a secondary result from being used to fill gaps in a primary analysis.

The record also demonstrates the limits of retrospective sample-size illustrations. Planning examples based on the observed secondary effect can show how assumed effect size relates to participant requirements under stated conditions. They are not observed power, do not establish the original design rationale, and may rely on an unstable pilot estimate. The registry does not report the original sample-size justification.

For biostatisticians and clinical researchers, the case highlights the value of reporting an interpretable primary contrast with uncertainty, alongside the analysis population, model specification, missing-data procedures, and multiplicity approach. Such information helps readers distinguish a descriptive pattern from a robust estimate and judge how much weight to place on secondary findings. The registry record supplies useful design and outcome information, but leaves important components of that assessment unreported.

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 limitations are specific to the information available for this trial. The primary endpoint is reported as a median rate with standard deviation, while the registry also labels the endpoint using median-time terminology. The record does not explain this characterization or show a two-arm comparison estimate. It explicitly notes that values were missing or not estimable for that comparison. Consequently, the principal endpoint has group summaries and a sponsor p-value but no reported effect magnitude or confidence interval.

The primary sponsor analysis is described only as logistic regression. The outcome coding, covariates, model assumptions, coefficient, and analysis population are not reported. Without those details, it is not possible to determine how the regression result corresponds to the posted median rate. The record also does not explain whether the discrepancy between the descriptive endpoint format and the analysis label reflects a particular transformation or modeling choice.

The secondary comparison is a recalculation from summary statistics rather than a sponsor-reported analysis. It is unadjusted and cannot account for participant-level covariates, missing observations, or any analytic choices not documented in the record. No multiplicity procedure is reported, so its p-value should not be interpreted as though it necessarily controlled for all outcomes or analyses.

Other important trial details are not reported in the registry record, including eligibility criteria, dose and treatment schedule, allocation procedure, adherence, missing-data handling, interim analyses, and the sample-size rationale. The arm descriptions are blank. The safety record lists adverse-event counts but does not provide event types beyond the absence of serious-event terms, or detailed event timing and ascertainment. These limitations restrict interpretation of the posted results and assessment of how broadly they may apply.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Varenicline (Chantix™) for the Treatment of Alcohol Dependence — NCT00705523.
• Registry record last updated 2015-06-02; status last verified 2015-06.
• Results first posted 2015-06-02.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT00705523 is a completed Phase II randomized, quadruple-masked, parallel-group pilot trial sponsored by the University of Pennsylvania. The registry lists enrollment of 40 and compares varenicline with placebo for alcohol dependence. The primary outcome is the rate of heavy drinking days per week over 12 weeks of treatment and one month of follow-up, based on self-report using the TLFB.

The posted primary medians are 0.89 for varenicline and 1.21 for placebo. The sponsor reports a logistic regression p-value of 0.10, but no primary comparison estimate or confidence interval is reported; the registry notes that a two-arm comparison was not estimable. The secondary alcohol composite score has posted means of 0.12 and 0.29. An unadjusted recalculation gives a mean difference of -0.17, with a confidence interval excluding zero and p = 0.012.

The registry reports no serious adverse events in either arm and lists other adverse events affecting 17 of 19 participants on varenicline and 19 of 21 on placebo. Multiplicity, missing-data procedures, analysis populations, and the original sample-size rationale are not reported in the registry record.