Pharmacokinetics of Oseltamivir Carboxylate In Morbidly Obese Subjects: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacokinetics of Oseltamivir Carboxylate In Morbidly Obese Subjects (NCT01179919), a na phase 1, phase 2 study. The primary outcome is Steady-State AUC of Oseltamivir Carboxylate.

2. Clinical Question

The study addresses a pharmacokinetic question: whether the exposure to oseltamivir carboxylate after the stated dosing schedule can be characterized in obese adults. It does not, on the information reported, directly test whether a dose changes clinical outcomes or compare treatment outcomes between obesity groups. The registry summary says the motivation was to assess whether the FDA-approved dose would achieve concentrations similar to those previously shown in non-obese volunteers. However, it does not report the non-obese reference data, a prespecified similarity margin, or an analysis comparing the study participants with that reference. Thus the broad motivation is clear, while the precise statistical criterion for judging similarity is not reported in the registry record.

3. Trial Design

The registry describes a completed, single-group drug study with allocation listed as not applicable and masking listed as none. The study is identified as Phase 1 and Phase 2. Its enrollment is 21. The intervention was oseltamivir, administered as 75 mg by mouth every 12 hours for 9 doses. The registry lists a start date of 2010-07 and a primary completion date of 2010-09. The listed condition is obesity.

A single-group design can describe pharmacokinetic measurements after participants receive a treatment, but it does not create a concurrent control comparison. In this study, there is no randomized arm receiving a different dose, placebo, or a non-obese comparator group. The registry summary refers to concentrations previously shown in non-obese volunteers as context for the question, but those observations are not described as a study arm. Whether the historical reference was selected in advance, and how any comparison with it was planned, is not reported in the registry record.

The primary endpoint is a continuous measure: steady-state AUC of oseltamivir carboxylate. The primary endpoint population is described as subjects who received all 9 doses. The recorded summary statistic is the mean, and the recorded dispersion measure is the standard deviation. The timeframe is 6 days. The registry also names steady-state maximum and minimum concentrations of oseltamivir carboxylate as secondary outcomes. The observed values for the primary and secondary outcomes are not reported in the registry record.

Although the registry entry is marked completed, completion status does not itself establish that outcome results or a statistical analysis are available in the record. It lists two outcome measures and no analyses. The protocol details beyond the dosing schedule and listed endpoints, including the pharmacokinetic sampling schedule, are not reported in the registry record. The record also does not describe an allocation procedure, which is consistent with the single-group design, or a masking procedure beyond stating that masking was none. The sample-size justification and any interim analyses 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Subjects who received all 9 doses of oseltamivir

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.

Population: Subjects administered at least 1 dose of oseltamivir

6. Primary Endpoint

The registry lists the primary outcome as Steady-State AUC of Oseltamivir Carboxylate, measured over 6 days.

The primary endpoint is steady-state AUC of oseltamivir carboxylate, expressed in hour*ng/mL. AUC is the area under a concentration-time curve: plasma concentration, measured in nanograms per milliliter, is considered across time in hours. Rather than representing a concentration at just one sampling point, AUC is intended to capture exposure over the measured interval. The registry gives the endpoint timeframe as 6 days and identifies the population as subjects who received all 9 doses of oseltamivir.

In pharmacokinetic studies, AUC is used to describe overall drug exposure under a specified dosing schedule. That makes it relevant to the registry’s stated question about whether the approved oseltamivir dose achieves concentrations in obese healthy volunteers similar to those previously shown in non-obese volunteers. AUC alone does not establish clinical benefit, nor does it show whether any observed exposure is sufficient for a particular clinical outcome. Those questions require evidence and criteria beyond the endpoint definition.

The registry specifies a mean as the summary measure and standard deviation as the dispersion measure. The mean would describe the average AUC in the analyzed population; the standard deviation would describe variation among the measured AUC values. Neither value is reported in the registry record. The record also does not report a confidence interval, an individual-level distribution, or a comparison with non-obese reference values. Consequently, the endpoint’s intended measurement is clear, but its observed magnitude and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s AUC is a quantitative measurement rather than a category such as event or no event. The registry specifies a mean and standard deviation as the summary statistics. In general, the mean gives the arithmetic center of measured values, while the standard deviation describes their spread. Reporting both can give a basic picture of an observed distribution, but they do not describe every feature of that distribution. For example, they do not by themselves establish whether values are symmetric or whether a small number of extreme observations influence the mean. The registry record does not provide the observed AUC values or an analysis of their distribution.

A standard deviation and a standard error answer different questions. The standard deviation describes variability among participants. A standard error describes uncertainty in an estimated statistic, such as a mean, under assumptions about sampling and the analysis. A confidence interval is commonly constructed to express that estimation uncertainty over a range of plausible values. These are general statistical distinctions. The registry identifies standard deviation as the dispersion measure, but it does not report an observed standard deviation, standard error, or confidence interval for the primary outcome. Thus the precision of the estimated mean cannot be evaluated from the record.

The AUC endpoint combines concentration and time, with units of hour*ng/mL. In general, a concentration-time curve can be summarized by the area under that curve, allowing the measurement to represent exposure over an interval rather than a single concentration reading. The registry names steady-state AUC and sets the timeframe at 6 days. It also lists steady-state Cmax and Cmin as secondary outcomes; these describe maximum and minimum concentrations at steady state. The registry does not provide the sampling times, assay details, calculation method, or observed values for these measures. Those methodological details are not reported in the registry record.

The endpoint population is subjects who received all 9 doses. That definition matters because a pharmacokinetic summary can depend on which participants and measurements contribute to it. In general, limiting analysis to participants who complete a dosing schedule may answer a question about exposure among those completing that schedule, while a broader analysis population may answer a different question. This is a general distinction, not a claim about the investigators’ analysis. The number of participants who received all 9 doses and the actual population used to calculate the outcome are not reported in the registry record.

The trial is single-group, with allocation listed as not applicable and masking listed as none. A single-group design can characterize measurements after a regimen, but it cannot by itself separate treatment-related changes from other influences using a concurrent randomized group. It also cannot directly estimate a between-group treatment contrast. The registry’s context invokes concentrations previously shown in non-obese volunteers, but those values are not included as a comparator arm or reported as data. How the historical observations were selected or compared is not reported in the registry record.

The registry reports an enrollment of 21 and says there are two outcome measures, but it lists no analyses. Enrollment is a design or record-level count; it does not establish the number contributing data to each endpoint. In general, sample size influences the precision of estimates, but the precision also depends on outcome variability and the analysis population. Here, the outcome variability and endpoint analysis count are not reported, so no estimate of precision should be inferred from enrollment alone.

The record includes assumptions for a planning illustration: two-sided significance level 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. It specifies that the illustration is computed from the observed effect, not from the trial’s own design. These assumptions describe a hypothetical planning exercise, not an observed analysis of this single-group study. Equal allocation between two arms does not describe the trial’s single-group structure. The illustration should therefore be read as a planning scenario rather than as the study’s original sample-size justification or evidence of observed power. The sample-size justification for the trial is not reported in the registry record.

For continuous outcomes, a normal approximation is a general method that can be used in planning or inference when its assumptions are suitable. The record does not describe diagnostic checks, transformation of AUC, treatment of extreme observations, or an alternative model. It also does not report a statistical plan or any inferential result. Accordingly, no particular analysis method beyond the stated summary measure and dispersion measure can be attributed to the investigators from the registry entry. Any recalculated estimate would require posted summary statistics; the record does not contain the values needed for such a recalculation.

Over-dispersion is a general concern when observed variability is greater than a model assumes. For continuous pharmacokinetic measurements, substantial variation can affect the uncertainty around an average and the suitability of a simple model. This is a general statistical consideration, not a reported finding about this study. The record provides no individual values, variance estimate, or model diagnostics with which to assess over-dispersion or other distributional features. It would be speculative to claim that the endpoint followed a particular distribution or required a particular correction.

Interpretation also depends on whether the question is estimation or comparison. A mean AUC can estimate average exposure in the analyzed group; a comparison with another group requires an identified comparator and a defined contrast. A claim of similarity requires more than a non-significant difference in a conventional test: generally, an acceptable difference must be defined and uncertainty assessed against that criterion. This explanation is general. The registry does not report a comparison method, margin, test, or confidence interval for the non-obese reference. Therefore, neither a formal similarity conclusion nor a treatment-group contrast can be reconstructed from the entry.

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("Oseltamivir Dosed Group")
n   <- c(19)
m   <- c(2579)
sp  <- c(510)
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  Oseltamivir Dosed Group  19  2579.000  510.000  2333.188  2824.812

11. Multiplicity, Missing Data and Analysis Populations

The registry names a primary endpoint, steady-state AUC of oseltamivir carboxylate, and a secondary outcome covering steady-state Cmax and Cmin. It lists two outcome measures and no analyses. The record does not report whether the outcomes were assigned a hierarchy for formal testing, whether any multiplicity adjustment was planned, or whether an outcome-specific analysis plan was prespecified. These details are not reported in the registry record.

Multiplicity is a general issue when several outcomes or comparisons are examined. Conducting multiple statistical tests can increase the chance of a seemingly notable result arising by chance, depending on the testing strategy. Whether adjustment is needed depends on the inferential goals and how outcomes are used. No such strategy can be inferred from the list of endpoints alone, particularly because no inferential results are reported.

The endpoint population is described as subjects who received all 9 doses. The number meeting that definition, the number with usable AUC measurements, and any departures from the intended dosing schedule are not reported in the registry record. The record does not say how missing measurements, incomplete dosing, withdrawals, or other unavailable outcome data were handled. It also does not state whether any imputation was used or whether analyses were restricted to observed measurements. It is therefore not possible to determine whether missingness could have affected the reported endpoint estimate.

The registry’s enrollment count does not resolve these questions. Enrollment and analysis populations can differ, and the actual analysis population is not reported. No participant-level accounting or reasons for exclusions are reported in the registry record. The record also does not describe an intention-to-treat framework or another analysis-population definition beyond the endpoint’s all-9-doses description. These omissions limit assessment of both completeness and the prespecification of the outcome analyses.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists 21 participants at risk for serious adverse events in the Oseltamivir Dosed Group and 0 affected by serious adverse events. For other adverse events, it lists 21 at risk and 1 affected. The serious adverse event terms list is empty. The death count is not reported in the registry record. These are the safety figures recorded for the group, not a comparison with another treatment or control group.

Counts should be read as descriptive registry entries. The record does not provide event descriptions for the other adverse-event category, details of timing or duration, severity classifications beyond the serious-event distinction, or a judgment about whether events were caused by oseltamivir. The absence of listed serious event terms does not supply those missing details, and the listed counts alone do not characterize the full safety profile.

The at-risk count is a registry field and should not be assumed to establish that every participant contributed complete safety follow-up. Follow-up duration and the process used to collect adverse events are not reported in the registry record. Because the study has a single group and no concurrent comparator, these counts cannot provide a comparative estimate of adverse-event risk. They describe only the entries recorded for the treated group.

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

The record documents a study of oseltamivir pharmacokinetics in obese adults, using 75 mg by mouth every 12 hours for 9 doses. Its primary endpoint is steady-state AUC of oseltamivir carboxylate over a timeframe of 6 days, with a mean and standard deviation specified as the intended summary. This identifies the measurement and the question the study set out to address. However, the registry record does not report the observed endpoint values, so it does not show the measured average exposure or variation among participants.

The study’s context is whether the FDA-approved dose would achieve concentrations similar to those previously shown in non-obese volunteers. The record does not report those reference concentrations, a concurrent non-obese group, or a prespecified criterion for similarity. It therefore does not establish similarity or a difference between obese and non-obese populations. The single-group design can describe exposure in participants receiving the regimen, but it does not itself provide a controlled group comparison.

The pharmacokinetic endpoint is not a clinical outcome. AUC characterizes exposure over time; it does not, on its own, indicate whether a treatment prevents or improves illness, or whether a dose is appropriate for a particular person. No clinical efficacy outcome is identified as the primary measure in the registry record. The study’s information should be understood as addressing a measurement question, not as a basis for medical advice.

The entry also does not support a conclusion about the precision of the primary estimate. Neither a confidence interval nor an observed standard deviation is reported, and the number included in the endpoint analysis is not reported. The enrollment of 21 does not fill those gaps. The listed safety counts are similarly descriptive and lack the detail needed to compare event risks or attribute events to treatment. Thus, the registry record establishes the study’s design, regimen, endpoints, and selected safety counts, but leaves the central outcome estimate and its uncertainty unreported.

14. Why This Trial Matters Statistically

This study illustrates why a clearly stated pharmacokinetic question and a reported outcome estimate are both needed for statistical interpretation. The registry defines the primary measure as steady-state AUC of oseltamivir carboxylate and identifies the population as participants who received all 9 doses. Those definitions describe what the measurement is intended to represent. Without the observed mean, standard deviation, analysis population size, or an uncertainty estimate, however, readers cannot assess the exposure estimate or its precision.

The design also highlights the distinction between describing a treated group and comparing groups. A single-group study can measure pharmacokinetic exposure under a specified regimen. It cannot make a concurrent randomized comparison with non-obese participants or another dose. Historical values may provide context, but a formal comparison depends on having the reference data, the method of comparison, and a criterion for interpreting the difference. Those elements are not reported in the registry record.

Another statistical lesson is that enrollment is not interchangeable with the analysis population. The record reports enrollment of 21, while the endpoint is defined for subjects who received all 9 doses. Because the number meeting that definition is not reported, readers cannot determine how many observations contribute to the primary estimate. This distinction is important for understanding both representativeness and uncertainty.

Finally, the record separates the study’s stated purpose from what can be concluded from posted results. The motivation concerns comparison of concentrations, while the posted registry information does not include the numerical endpoint results or a comparative analysis. Recognizing that gap prevents a study objective from being mistaken for a finding. The entry remains useful for identifying the design, regimen, endpoints, and reporting limitations, but it does not resolve the stated pharmacokinetic question on its own.

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 central limitation for interpreting this trial record is that the primary endpoint’s observed mean and standard deviation are not reported. No confidence interval or other measure of uncertainty is reported either. Consequently, the registry does not provide the estimate needed to describe the measured steady-state AUC or its precision. The listed enrollment of 21 cannot substitute for those results.

The study is single-group and has no concurrent comparator. Although the registry summary frames the question against prior concentrations in non-obese volunteers, the record does not provide those concentrations, explain how they were obtained, or specify a formal comparison. A similarity margin and a comparison analysis are also not reported. This limits what can be concluded about exposure relative to non-obese volunteers.

The primary population is described as subjects who received all 9 doses, but the number in that population is not reported. The record does not state how many participants had usable endpoint data, whether dosing or sampling was incomplete, or how missing measurements were handled. Those omissions make it difficult to assess the completeness of the endpoint analysis and the possibility that the analyzed participants differed from those enrolled.

Other trial details relevant to interpretation are not reported in the registry record, including the pharmacokinetic sampling schedule, assay methods, observed Cmax and Cmin values, and statistical analysis plan. The record lists no analyses. It also does not report participant characteristics beyond obesity and the summary’s description of healthy volunteers, so the population cannot be characterized in greater detail from this entry.

Safety reporting is limited to the recorded serious and other adverse-event counts. The serious-event terms are not listed, the death count is not reported, and detailed event descriptions and follow-up information are absent. These limitations apply to the registry record and do not establish whether additional information exists elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pharmacokinetics of Oseltamivir Carboxylate In Morbidly Obese Subjects — NCT01179919.
• Registry record last updated 2017-02-09; status last verified 2016-12.
• Results first posted 2016-12-06.
• 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

The registry record describes a completed Phase 1 and Phase 2, single-group study of oseltamivir in obese adults, with enrollment of 21. Participants in the Oseltamivir Dosed Group received 75 mg by mouth every 12 hours for 9 doses. The primary endpoint was steady-state AUC of oseltamivir carboxylate, measured over 6 days and intended to be summarized by a mean and standard deviation. Steady-state Cmax and Cmin were listed as secondary outcomes.

The record lists two outcome measures and no analyses. It does not report the primary outcome values, the endpoint analysis population count, or a comparison with non-obese reference concentrations. Safety entries list 0 affected by serious adverse events and 1 affected by other adverse events among 21 at risk; the death count is not reported in the registry record. The design and endpoint are documented, but the numerical results needed to evaluate the main pharmacokinetic question are not reported.