Lofexidine for Management of Opioid Withdrawal With XR-NTX Treatment: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Lofexidine for Management of Opioid Withdrawal With XR-NTX Treatment (NCT04056182), a na phase 2 study. The primary outcome is Successful Vivitrol Induction.

2. Clinical Question

The trial examined whether participants with opioid-use disorder who began a detoxification and induction process while receiving lofexidine were subsequently inducted onto Vivitrol, an extended-release naltrexone injection. It was an open-label pilot, with lofexidine used before the injection during a flexible detoxification lasting 2 to 10 days.

This question is about completion of a specified treatment-initiation process, not a randomized estimate of lofexidine's effect relative to another medication or to no lofexidine. The registry describes the study as a safety and tolerability pilot. As an open-label single-group study, its outcome can describe what happened in the enrolled group, but cannot by itself separate the contribution of lofexidine from other aspects of care or participants' circumstances. The primary endpoint result is not reported in the registry record, so the recorded information does not answer how many participants were inducted.

3. Trial Design

This is a phase 2, open-label pilot trial registered as a single-group study. The record lists enrollment of 20 and the status as completed. The sponsor is New York State Psychiatric Institute. The record lists a start date of 2019-09-01 and a primary completion date of 2021-01-29.

Participants received lofexidine during an outpatient detoxification and induction process intended to conclude with an injection of XR-Naltrexone, identified in the registry description as Vivitrol. The detoxification was flexible and lasted 2 to 10 days. Lofexidine is described as three 0.18mg tablets taken orally 4 times daily at 4-to 6-hour intervals for 2-10 days before receiving Vivitrol. No randomized allocation or masking is recorded.

The primary measure is a count of participants inducted onto Vivitrol. Its stated population is people who enrolled and initiated detoxification and induction, and its timeframe is up to 10 days of detoxification and induction. Although the record reports one outcome measure, it lists no analyses. It does not include the observed primary outcome count, an estimate of uncertainty, or a comparative analysis.

The trial's single-group structure is central to interpretation. The outcome can describe induction in this enrolled cohort if a result is available, but there is no like-for-like control group in the registry record to support a treatment contrast. The registry also does not report a protocol rationale for the enrollment target, a detailed statistical analysis plan, or details of participant flow beyond the outcome's stated population.

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: number of individuals who enrolled in the trial and initiated the detoxification/induction process

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 Successful Vivitrol Induction, measured over up to 10 days of detoxification and induction.

The primary endpoint is the number of participants inducted onto Vivitrol. It is defined as a count among individuals who enrolled and initiated the detoxification and induction process, measured over up to 10 days of detoxification and induction. This is a binary-outcome summary expressed as a count: each eligible participant either contributes to the induction count or does not.

A count is useful for describing whether a treatment-initiation pathway was completed in the group studied. It is directly interpretable as the number of people reaching the defined milestone, rather than as a laboratory value or a time-to-event estimate. The endpoint also matches the trial's stated focus on managing withdrawal symptoms while initiating outpatient treatment with naltrexone. It does not, by itself, measure withdrawal severity, duration of symptoms, or the comparative effect of lofexidine.

The registry defines the measure and its timeframe but does not report the observed count. Consequently, the endpoint's magnitude in this trial, and how precisely it was estimated, cannot be assessed from the registry record. No confidence interval or other uncertainty measure for this endpoint is reported there.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The main statistical feature of this study is its single-group design. In a single-group study, outcomes are described for participants receiving the study intervention, rather than estimated as a contrast between concurrently randomized groups. Here, the registry lists allocation as NA, masking as none, and the model as single group. A count of participants inducted onto Vivitrol would describe the observed cohort, but would not provide a randomized estimate of what would have happened under a different intervention.

What does a count endpoint convey?

A count records how many participants meet a defined outcome. The registry's primary measure is the number inducted onto Vivitrol among people who enrolled and initiated detoxification and induction, within up to 10 days of that process. A count is straightforward to understand, but its interpretation depends on a clearly defined population and complete outcome ascertainment. The registry describes the endpoint population, but does not report the observed count or explain how outcomes were handled when induction status was unavailable.

Counts alone do not describe sampling uncertainty. A confidence interval is a statistical range intended to express uncertainty around an estimate under stated assumptions. In general, such an interval can help readers distinguish a well-estimated quantity from one with substantial uncertainty. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from this record.

What can a single-group result establish?

In general, a single-group outcome can show what was observed among the people studied under the recorded treatment process. It cannot directly answer a comparative question because there is no concurrent control group. Randomization, when used, helps balance measured and unmeasured factors on average across groups; that protection is not available in this single-group design. As a result, even a reported induction count would not isolate the effect of lofexidine from the rest of the care pathway or from factors that may affect completion.

The study is open-label, so masking is not recorded. In general, lack of masking can influence care decisions, participant experience, and outcome assessment, depending on the outcome and procedures. Induction onto Vivitrol is a concrete milestone, but the registry does not describe independent outcome adjudication or procedures to limit assessment bias. Those details are not reported in the registry record.

How should planning illustrations be read?

The registry information describes a separate planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It frames the effect to detect as a stated fraction of an observed effect. For time-to-event calculations, the illustration concerns total events under the Schoenfeld approach; other calculations are expressed as participants per arm. These are planning conventions, not a description of the trial's actual design, which is single-group.

The illustration is not observed power. In general, power calculations describe the chance that a planned statistical procedure will identify an effect under chosen assumptions; they do not measure the strength of evidence after a study is complete. Planning numbers are not outcomes and do not show that a treatment effect was present. The primary endpoint result needed to understand an observed effect is not reported in the registry record. The study's own sample-size justification and detailed planning rationale are also not reported there.

Why does over-dispersion matter in general?

Over-dispersion arises when outcome variability is greater than a statistical model assumes. It can make standard errors too small and confidence intervals too narrow if the model does not allow for the extra variability. This is a general consideration for count outcomes, but the primary endpoint is reported as a participant count, and the registry does not describe a count regression model or a dispersion estimate. There is no reported basis for concluding that over-dispersion was assessed or relevant to the analysis.

The registry lists no analyses. It therefore does not state a model, an inferential procedure, an adjustment strategy, or a method for handling missing endpoint values. Without these details and without the primary result, statistical interpretation is limited to the design and definitions in the record, rather than an assessment of an estimated treatment effect.

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("Lofexidine")
n      <- c(20)
events <- c(10)
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  Lofexidine  20  10  50.0  27.2  72.8  29.9  70.1  29.8  70.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no analyses. It does not report whether the primary endpoint was tested using a formal hypothesis test, whether additional outcomes were collected but not listed, or whether any interim analyses were conducted. Those matters are not reported in the registry record.

Multiplicity refers, in general, to the statistical issue created by making several inferences, such as testing multiple outcomes or examining multiple timepoints. When many tests are conducted, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the testing strategy. The registry information does not describe a multiplicity procedure or a broader testing plan, so no conclusion about adjustment can be drawn.

The primary endpoint population is described as people who enrolled and initiated detoxification and induction. The record does not report whether all participants in that population had ascertainable induction status, how missing outcome data were handled, or whether any participants were excluded from an analysis. It also does not report an intention-to-treat, per-protocol, or other analysis-population definition. The endpoint's stated population is not enough to determine the actual analysis set.

In general, missing outcomes can affect interpretation when the likelihood of missingness is related to participants' circumstances or outcomes. Methods such as imputation or sensitivity analysis may be used in some studies, but no such approach is reported. There is no reported missing-data count for the primary outcome, so the extent of this issue cannot be assessed from the registry record.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: inpatient detoxification (5.0%), myocardial infarction (5.0%).

The registry lists safety counts for the lofexidine group. Serious adverse events affected 2 participants among 20 at risk; other adverse events affected 12 participants among 20 at risk; and deaths were 0. These categories should be read as separate registry summaries. The record does not explain whether a participant could contribute to more than one category, so the figures should not be combined or treated as mutually exclusive.

The top serious-event terms are inpatient detoxification and myocardial infarction, each listed as 5.0%. The registry does not provide additional details in the record about event timing, severity beyond the serious classification, clinical course, or the basis for attributing an event to treatment. The event terms and percentages are descriptive entries, not proof that lofexidine caused the events.

Because the study has no concurrent comparator, these figures cannot establish whether event frequency was higher or lower than it would have been under another approach. A small pilot safety summary can identify events recorded during the study, but cannot by itself resolve comparative safety. The registry record does not report a broader safety analysis or statistical comparison.

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

The record describes a completed phase 2 pilot in which lofexidine was used during a flexible detoxification and induction process intended to end with Vivitrol. It makes the study's primary question clear: how many participants who began the process were inducted onto Vivitrol within up to 10 days. The record does not report the answer to that question. Therefore, it does not support a statement about the observed frequency of induction or the precision of an estimated frequency.

The study design also shapes what its results could mean. With a single group and no comparator, an observed outcome would characterize this cohort and treatment process. It could not establish that lofexidine itself caused a particular induction outcome. The same design limitation applies to adverse events: event counts are descriptive and do not provide a comparative estimate of risk.

The safety entries show serious adverse events affecting 2 participants among 20 at risk, other adverse events affecting 12 among 20 at risk, and 0 deaths. Inpatient detoxification and myocardial infarction are listed as serious-event terms at 5.0% each. These data should not be interpreted as a causal verdict about lofexidine, nor as evidence that the intervention is safe or unsafe relative to an alternative.

The record can establish that this pilot was conducted and can describe its stated design, endpoint definition, and posted safety counts. It cannot answer the primary endpoint question from the information recorded, provide a controlled estimate of treatment effect, or quantify uncertainty around the induction outcome. The registry does not report an analysis plan, missing-outcome handling, or an analysis population, which further limits statistical assessment.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of how a meaningful clinical milestone can be framed as a count while still leaving important interpretive questions unanswered. Induction onto Vivitrol is the defined primary outcome, and the registry specifies the population and timeframe. Yet the outcome count itself is not reported in the registry record. A carefully defined endpoint does not substitute for the observed result needed to assess its magnitude.

The design also makes the distinction between description and comparison especially important. A single-group pilot can provide descriptive experience with a treatment-initiation process, but it does not provide a randomized control contrast. Readers should not mistake a cohort outcome for evidence that the intervention produced that outcome, or infer what would have occurred under another care pathway.

The planning assumptions illustrate another statistical distinction: sample-size planning is not the same as analysis of observed trial data. The record describes an illustration using assumptions for a two-arm comparison, even though this registered trial is single-group. Such planning conventions do not turn the pilot into a comparative trial, and planning calculations are not evidence of observed treatment effects or observed power.

Finally, the safety counts demonstrate why event definitions and denominators matter. Serious events, other events, and deaths are reported separately, and the listed serious-event terms are descriptive. Without comparative data and further event details, these counts should not be converted into causal claims. The record's limitations are therefore not only about sample size; they concern the missing primary outcome result, absent comparison, and unreported analysis details.

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 immediate limitation of the registry record is that it does not report the primary outcome count. Although the outcome, population, and timeframe are defined, no observed induction result or uncertainty estimate is available. This prevents assessment of the main outcome the trial set out to measure.

The single-group, open-label design has no concurrent comparator and no recorded masking. Any outcome or adverse event count would therefore be descriptive rather than a controlled estimate of the effect of lofexidine. The registry record does not report detailed eligibility criteria, participant flow, reasons for not reaching induction, or how induction status was verified. These details are not reported in the registry record.

The record lists no analyses. It does not report the statistical method for the endpoint, an analysis population, a missing-data approach, or whether any interim analyses occurred. A sample-size justification for the trial itself is not reported; the planning illustration is not a substitute for that justification and uses two-arm planning assumptions distinct from the registered single-group design.

Safety interpretation is also constrained. The record gives affected counts and selected serious-event terms but does not provide event-level timing, duration, severity detail, or a comparative safety group. It does not establish whether the events were related to the intervention. The posted information is therefore insufficient for a causal or comparative safety conclusion.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Lofexidine for Management of Opioid Withdrawal With XR-NTX Treatment — NCT04056182.
• Registry record last updated 2021-12-09; status last verified 2021-12.
• Results first posted 2021-12-09.
• 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

NCT04056182 is a completed phase 2, open-label, single-group pilot sponsored by New York State Psychiatric Institute. It studied lofexidine during outpatient opioid detoxification and induction onto XR-Naltrexone (Vivitrol), with a flexible detoxification process lasting 2 to 10 days. The registry lists enrollment of 20 and identifies successful Vivitrol induction as the primary outcome.

The primary measure is the number of participants inducted onto Vivitrol among those who enrolled and initiated detoxification and induction, within up to 10 days. The observed primary outcome is not reported in the registry record, and no analyses are listed. Safety entries report serious adverse events affecting 2 participants among 20 at risk, other adverse events affecting 12 among 20 at risk, and 0 deaths. With no comparator and limited analysis details, the record supports description of the design and posted safety counts, but not a comparative treatment-effect conclusion.