Pharmacokinetic and Pharmacodynamic Effects of Passive Cannabis Inhalation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacokinetic and Pharmacodynamic Effects of Passive Cannabis Inhalation (NCT01798186), a randomized phase 1 study. The primary outcome is Delta-9-tetrahydrocannabinol (THC) Cmax in Blood.

2. Clinical Question

3. Trial Design

The registry identifies this as a Phase 1, randomized, single-masked, parallel study. Randomization indicates that assignment to study conditions was intended to use a random process. The record does not describe the randomization sequence, allocation concealment, or the people who were masked. It also does not report further protocol details explaining how exposure sessions were conducted.

The listed conditions compare passive exposure to cannabis smoke with 5% THC and no ventilation, 11% THC and no ventilation, or 11% THC with active ventilation. The 11% THC conditions therefore differ in ventilation, while the no-ventilation conditions differ in stated THC concentration. The record does not describe a factorial analysis or a prespecified plan for interpreting these contrasts, so the condition descriptions alone should not be treated as a complete account of the planned comparisons.

The registry lists enrollment of 26. The posted primary-outcome summaries give n=6 for each listed arm. The reason the enrollment figure and the arm-level outcome counts differ is not reported in the registry record; the enrollment figure should not be assumed to represent the analysis population for this outcome.

The study is marked completed. Its recorded start is 2013-05 and its primary completion is 2013-08. The primary outcome is blood THC Cmax, with a stated assessment timeframe of 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 22, 26, 30, and 34 hours post cannabis exposure. The registry also lists oral-fluid THC Cmax and subjective VAS drug effect as secondary outcomes. Details of participant characteristics, follow-up completion, and analysis populations 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.

Before assignment: Participants were randomized to 3 experimental sessions. Additionally, participants were recruited to smoke cannabis in order to generate the smoke that was passively inhaled by the experimental groups.

Overall Study

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 Delta-9-tetrahydrocannabinol (THC) Cmax in Blood, measured over 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 22, 26, 30, and 34 hours post cannabis exposure.

The primary endpoint is the maximum concentration, or Cmax, of delta-9-tetrahydrocannabinol (THC) measured in blood after exposure. It is reported in ng/mL, with the mean and standard deviation for each listed condition. In general, Cmax is used in pharmacokinetic studies to describe the peak measured concentration over a defined sampling period. It can summarize the concentration profile in a single value, but it does not by itself describe how long a concentration persisted or the full pattern of change over time.

The registry lists blood collection timepoints from 0.25 through 34 hours post cannabis exposure. The record does not specify how the maximum was selected from the measurements, how values below an assay’s detection limit were handled, or whether the reported peak was observed directly or estimated. Those details matter when interpreting a peak based on repeated measurements.

The posted means are 1.4 ng/mL for 5% THC cannabis without ventilation, 3.07 ng/mL for 11% THC cannabis smoke without ventilation, and 0.5 ng/mL for 11% THC cannabis with ventilation. The corresponding standard deviations are 0.5, 1.6, and 0.4. These are descriptive summaries of the endpoint. They do not, on their own, establish the precision of a between-condition contrast or whether any difference is statistically distinguishable from chance.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports the primary outcome as a continuous measure summarized by its mean and standard deviation. In general, a mean is the arithmetic average of observed values, and the standard deviation describes how dispersed those values are around the mean. These summaries are useful for describing an arm, but neither supplies a direct estimate of uncertainty in a difference between arms.

What does Cmax represent?

In general, Cmax is the highest concentration recorded or estimated during a defined observation period. The registry names blood THC Cmax as the primary endpoint and lists repeated collection times after exposure. It does not explain the operational rule used to obtain each participant’s Cmax from those measurements. If measurements are sparse, a true peak between collection times may not be captured; this is a general consideration, not a claim about what happened in this study.

The timepoints in the record run from 0.25 to 34 hours post cannabis exposure. Repeated measurements can characterize concentration over time, while Cmax compresses that trajectory into a peak value. Other aspects of the concentration profile, such as timing of the peak or persistence, cannot be recovered from the reported mean Cmax and standard deviation alone.

How should the arm summaries be read?

The posted arm summaries report the mean and standard deviation separately for each exposure condition. The mean is not an estimate of the difference between conditions. To make a comparative claim, an analysis would ordinarily specify a contrast and quantify its uncertainty, for example with a confidence interval, and may also report a test result. No such primary-outcome analysis is reported in the registry record. Confidence intervals and p-values are not reported for the endpoint.

In general, a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the analysis. It is not the range containing every participant’s value, and it is not a guarantee that the true value lies within the interval. Since the record does not report confidence intervals for the arm means or their contrasts, the precision of those estimates cannot be assessed from the posted summaries alone.

Why can spread matter?

The standard deviations vary across the reported conditions. In general, greater dispersion can make a mean less precise when the amount of information is otherwise similar. For count outcomes, over-dispersion means the observed variability exceeds what a particular model assumes; it can make standard errors and tests unreliable if ignored. The primary outcome is continuous, and the record does not report a model or an over-dispersion assessment. The general concept should not be taken as evidence that over-dispersion was present in this study.

The outcome summaries have n=6 in each listed arm. Small arm-level counts can make estimates sensitive to individual observations, but the degree of sensitivity cannot be determined without individual data. The standard deviations provide a description of spread, not a substitute for the individual observations or an inferential model.

What do the planned sample-size calculations mean?

In general, a sample-size calculation for a future study depends on an assumed effect, variability, significance level, allocation, and target power. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of the observed effect. Such planning values, when available, are illustrations based on assumptions; they are not observed findings and are not observed power for this trial.

The record indicates that values are missing or not estimable for a two-arm comparison of this continuous endpoint. Consequently, the reported details do not support a numerical planning estimate for that comparison. A planning illustration should not be interpreted as a recommendation for a future trial or as evidence that this trial had a particular probability of detecting an effect.

What analysis details are absent?

The registry reports no analyses for the posted outcome. It does not report a statistical model, covariate adjustment, handling of repeated measurements, a prespecified contrast, or an approach to multiplicity. It also does not report a missing-data method or an analysis population definition. These omissions prevent readers from reconstructing an inferential analysis or determining whether the descriptive summaries match the original analysis plan.

Randomization is reported, but randomization alone does not specify how outcome data were analyzed. In general, a randomized design can support comparisons under appropriate analysis assumptions, but interpretation still depends on which participants and measurements were included, how missing observations were handled, and what comparisons were planned. Those details are not reported in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("5% THC Cannabis, no Vent", "11% THC Cannabis Smoke, no Vent", "11% THC Cannabis, Vent")
n   <- c(6, 6, 6)
m   <- c(1.4, 3.07, 0.5)
sp  <- c(0.5, 1.6, 0.4)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  5% THC Cannabis, no Vent  6  1.400  0.500  0.875  1.925
CARM  11% THC Cannabis Smoke, no Vent  6  3.070  1.600  1.391  4.749
CARM  11% THC Cannabis, Vent  6  0.500  0.400  0.080  0.920

11. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary blood THC Cmax outcome and two secondary outcomes: oral-fluid THC Cmax and subjective VAS drug effect. It does not report a multiplicity strategy, such as a prespecified hierarchy or adjustment across outcomes. In general, when several outcomes or contrasts are tested, the chance of at least one false-positive finding can increase unless the analysis plan accounts for multiple testing. No claim about the study’s actual testing burden or adjustment can be made from the registry record.

The registry entries give descriptive blood Cmax summaries, but do not provide results for the listed secondary outcomes. The record also reports no analyses for the outcome summaries, so there are no reported inferential results to assess across endpoints or contrasts.

Missing-data handling is not reported in the registry record. The primary outcome summaries have n=6 in each listed arm, while the registry lists enrollment of 26. The record does not explain the difference, identify missing measurements, give reasons for missingness, or state whether all randomized participants were included in the summaries. It also does not define an intention-to-treat, per-protocol, or other analysis population.

In general, missingness can affect interpretation if the availability of measurements is related to participant characteristics or outcomes. Without a participant flow, missing-data description, or analysis-population definition, it is not possible to assess that issue for this study. The posted arm summaries should therefore be understood as descriptive results for the reported outcome counts, not necessarily as summaries of every participant enrolled or assigned.

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 5% reporting threshold.

The registry reports serious adverse event figures for each listed exposure group. For each group, the number at risk for serious adverse events is 6 and the number affected is 0. The reported deaths are also 0 in each group. The record lists no serious adverse event terms.

For other adverse events, each group has 6 at risk and 0 affected. These are the figures recorded for the groups; they do not establish that no adverse events of any kind occurred outside the registry’s recorded categories or reporting period. The record does not provide definitions of adverse-event collection, attribution, severity grading, or duration of follow-up.

Zero recorded events in these groups should not be read as proof that an event is impossible or that the study establishes safety. In general, absence of recorded events is different from evidence that risk is absent, especially when the available group counts are limited. The adverse-event figures are descriptive registry data and should be interpreted with the study’s size and reporting details in mind.

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

The posted results describe blood THC Cmax after passive exposure under the listed conditions. They report a mean and standard deviation for each condition, with n=6 per arm. These figures provide a snapshot of the recorded peak blood concentration values and their within-arm spread.

They do not establish a statistically significant difference between conditions. The registry record does not report an inferential comparison, confidence interval, or p-value for the primary endpoint. The means cannot, on their own, show whether observed differences are precise, reproducible, or attributable to a particular feature of the conditions.

The conditions vary in THC concentration and ventilation, but the posted summaries do not isolate those factors through reported contrasts. The registry does not report the statistical plan or the analyses needed to distinguish the contribution of each condition feature. The summaries also do not establish the duration of any concentration pattern, since the reported endpoint is Cmax rather than a complete time-course analysis.

The study’s stated aim includes toxicological analysis of oral fluid, urine, and blood after passive cannabis-smoke exposure. The available primary endpoint results concern blood Cmax only. They do not establish oral-fluid or urine findings, whether a toxicology test would be positive, or how long any positive result might persist. The secondary outcomes are listed, but their results are not reported in the registry record for this analysis.

Nor do the summaries establish how broadly the findings apply beyond the study conditions. Participant characteristics, assay details, exposure procedures beyond the brief condition descriptions, and the reason for the difference between enrollment and outcome counts are not reported in the registry record. The most defensible reading is therefore descriptive: the record gives arm-level blood Cmax summaries, while leaving comparative uncertainty, completeness of outcome data, and broader interpretation unresolved.

14. Why This Trial Matters Statistically

This trial is statistically interesting because its exposure conditions vary along features that are relevant to interpretation: THC concentration and ventilation. The posted endpoint summaries allow readers to see the reported mean blood Cmax and variability for each condition. That is useful descriptive information, but it also illustrates why arm summaries should not be mistaken for a controlled estimate of a specific contrast.

In general, interpreting a randomized study requires a clear comparison, an estimate of that comparison, and an account of its uncertainty. Here, the registry identifies randomization and reports arm-level results, but does not report an inferential analysis for the primary endpoint. Without a reported contrast and confidence interval, readers cannot judge the precision of a difference using the registry results alone.

The record also illustrates the importance of connecting enrollment, analysis counts, and missing-data reporting. Enrollment is listed as 26, while the primary outcome summaries have n=6 in each condition. The reason for this difference is not reported. That gap leaves uncertainty about which measurements contributed to the summaries and whether the arms represent all assigned participants.

Finally, the endpoint is a peak concentration measured during a specified series of collection times. This is a focused pharmacokinetic summary, not a complete account of exposure or toxicological detection. The broader question raised by the study requires attention to other biological specimens, time patterns, and assay procedures, none of which can be resolved from the blood Cmax summaries alone. The statistical value of the record is therefore both its descriptive reporting and the clear limits of what those summaries support.

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 registry description does not provide participant demographics, eligibility criteria, or detailed exposure procedures. It gives brief descriptions of the THC concentrations and ventilation conditions, but does not report the duration or other operational details of exposure. Those omissions limit assessment of how closely the listed conditions correspond to a particular real-world exposure setting.

Although the study is identified as randomized and single-masked, the record does not identify who was masked, explain the randomization process, or describe allocation concealment. It does not report a protocol-level statistical plan, prespecified contrasts, covariate adjustments, or a method for analyzing the repeated concentration measurements.

The primary endpoint summaries include n=6 per arm, while the listed enrollment is 26. The reason for that difference, participant flow, and any exclusions are not reported in the registry record. The record also does not explain missing outcome data or define the population used for analysis.

For blood THC Cmax, the record does not state the assay method, detection limits, handling of values below those limits, or how Cmax was derived from the timepoint measurements. It provides arm means and standard deviations but no confidence intervals or inferential comparisons. Results for the listed secondary outcomes are not included in the registry record. These limitations constrain both the statistical interpretation and the ability to connect the blood endpoint to the study’s wider toxicology aims.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pharmacokinetic and Pharmacodynamic Effects of Passive Cannabis Inhalation — NCT01798186.
• Registry record last updated 2017-08-03; status last verified 2017-08.
• Results first posted 2017-08-03.
• 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

The registry identifies a completed, randomized, single-masked, parallel Phase 1 study of passive cannabis-smoke exposure. The listed conditions are 5% THC without ventilation, 11% THC without ventilation, and 11% THC with ventilation. The primary endpoint is mean blood THC Cmax in ng/mL, assessed after exposure across the stated collection timepoints.

The posted arm summaries report means of 1.4, 3.07, and 0.5, with standard deviations of 0.5, 1.6, and 0.4, respectively; each arm summary has n=6. The registry lists enrollment of 26, but does not explain the difference between that figure and the outcome counts. No inferential analysis for the primary outcome is reported. The registry also lists oral-fluid THC Cmax and subjective VAS drug effect as secondary outcomes, without results in the registry record for this analysis.

Serious adverse events, other adverse events, and deaths are recorded as 0 in each listed group. Details about adverse-event collection and analysis are not reported in the registry record.