Multi-dose Pharmacokinetics and Dose Ranging of Inositol in Premature Infants (INS-2): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Multi-dose Pharmacokinetics and Dose Ranging of Inositol in Premature Infants (INS-2) (NCT01030575), a randomized phase 2 study. The primary outcome is Population Pharmacokinetics: V - Volume.

2. Clinical Question

The study rationale in the registry record is that maintaining inositol concentrations similar to those occurring naturally in utero might reduce retinopathy of prematurity and bronchopulmonary dysplasia. That rationale is not itself evidence of a clinical effect. The primary outcome focuses on pharmacokinetics, while listed secondary outcomes include ophthalmologic diagnoses and treatments, retinopathy of prematurity, and neurodevelopmental impairment or death at follow-up. The registry record does not report results that establish whether any dose changed these clinical outcomes.

3. Trial Design

This was a Phase II, randomized, placebo-controlled, parallel-group study. The registry classifies its masking as quadruple; the official title calls it double-masked. The record does not explain this difference in wording, so the masking procedures cannot be described further from the registry information alone.

The four assigned groups received 10 mg/kg/day, 40 mg/kg/day, or 80 mg/kg/day of 5% inositol, or 5% glucose placebo. The brief description says daily treatment began within 72 hours after birth and continued until infants reached 34 weeks post-menstrual age, 10 weeks chronologic age, or hospital discharge, whichever occurred first. Treatment was initially administered intravenously; with progression to full feeding, it was administered enterally, orally or by feeding tube. The record describes a follow-up examination at 18-22 months corrected age.

The registry lists enrollment of 125. The brief description, which presents the study as a pilot, says an estimated 96 infants would be enrolled at 17 NICHD Neonatal Research Network sites. These are distinct statements in the record: the estimate is not the same as the listed enrollment. The study is marked completed, with a start date of 2010-01 and primary completion date of 2011-05.

For pharmacokinetic analyses, the record says all four arms were used. One infant randomized to placebo incorrectly received the low dose; this infant was included in the low-dose arm for pharmacokinetic analyses and in the randomized placebo arm for other analyses. Further detail on randomization procedures, allocation concealment, and masking implementation is not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: All 4 arms of the study are used in the Pop-PK analysis population. 1 infant randomized to the placebo arm incorrectly received the low dose. The infant was included in the low dose arm for the pharmacokinetics analyses and as randomized to the placebo arm for all other analyzes.

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 Population Pharmacokinetics: V - Volume, measured over 8-10 blood samples per infant were drawn over 10 weeks for infant safety with the full study duration represented across all infants. Samples were drawn at baseline & on days 1, 2, 4, 6, 8, 10, 12, 14, 16, 20, 24, 28, 35, 42, 56, and 70..

The primary outcome is population pharmacokinetic volume, labelled V, measured in l/kg and reported as a mean with standard error. In pharmacokinetics, volume of distribution is a model-based quantity describing the apparent extent to which a substance is distributed relative to its concentration in the measured compartment. It is not a direct measurement of a physical body space. The registry record does not provide a fuller endpoint definition or describe the model used to estimate V.

The outcome is intended to characterize how inositol behaves in the body under repeated dosing. Pharmacokinetic information can help describe exposure and differences in disposition across a population, which is relevant when evaluating dose levels. It does not, by itself, establish an effect on retinopathy of prematurity, bronchopulmonary dysplasia, survival, or later neurodevelopment.

Blood and urine levels are described as being measured after repeated doses. For the primary population pharmacokinetic outcome, 8-10 blood samples per infant were drawn over 10 weeks, with the full study duration represented across infants. The record lists baseline and days 1, 2, 4, 6, 8, 10, 12, 14, 16, 20, 24, 28, 35, 42, 56, and 70 as sampling times. No mean V estimate, standard error, confidence interval, or arm-specific primary result is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study has four randomized parallel groups: three inositol dose levels and a glucose placebo. In a parallel-group design, participants remain assigned to one group rather than crossing among treatments. Random allocation is intended to make treatment groups comparable on average, although the registry record does not describe the sequence-generation or concealment methods. The record labels the study randomized and reports quadruple masking, while its official title says double-masked; operational details are not reported in the registry record.

The primary outcome is a continuous pharmacokinetic quantity, V, expressed in l/kg. The specified summary is the mean with standard error. A mean describes the average value in the analysed population. A standard error describes the sampling uncertainty of an estimated mean, rather than the spread of individual measurements. General statistical note: a confidence interval is often used to show uncertainty around an estimate, but the registry record does not report one for V.

The primary outcome is described as population pharmacokinetics. That typically involves estimating parameters that characterize drug disposition across a group, rather than reporting a simple value from one measurement per infant. This is a general explanation; the model form, estimation method, covariates, and handling of below- or above-range measurements are not reported in the registry record. It is therefore not possible to assess the model assumptions or reproduce the estimate from the registry description.

Repeated sampling is central to this outcome. The record describes 8-10 blood samples per infant over 10 weeks and lists sampling times from baseline through day 70. Sampling across time can provide information about concentration patterns after dosing. The record says the full study duration was represented across all infants, but does not state that every infant contributed a sample at every listed time. The schedule should not be read as evidence that all listed samples were available for each participant.

The record identifies a deviation between randomized assignment and treatment received for one infant. For pharmacokinetics, this infant was included in the low-dose group; for other analyses, the infant remained in the placebo group as randomized. General statistical note: analyses grouped by randomized assignment preserve the original treatment comparison, while analyses grouped by treatment received describe exposure more directly but can be affected by departures from random assignment. The record does not report additional sensitivity analyses or explain whether this handling was prespecified.

The safety data give numbers of participants at risk and numbers affected for serious and other adverse events, plus death counts. These are descriptive summaries. A participant count is not the same as an event count: the registry labels the measure as participants with events, but does not describe recurrence or how multiple events within a participant were handled. No statistical comparisons or uncertainty estimates for the safety groups are reported in the registry record.

General statistical note: over-dispersion occurs when observed variability exceeds what a chosen probability model assumes. It can make standard errors too small if the model does not accommodate the extra variability. This concern can arise in analyses of counts, but the registry record does not specify a count model for the clinical outcomes or report a diagnostic assessment, so no claim can be made about whether over-dispersion was relevant in this study.

The record lists 21 outcome measures and no analysis entries. It does not report the statistical analysis plan, model details, hypothesis tests, missing-data procedures, interim analyses, or multiplicity adjustments. The record’s planning description for sample-size illustrations states that they use an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; these are planning illustrations, not a report of the trial’s design justification or observed power. The illustrations are not numerical primary results and do not fill the gap in reported outcome estimates.

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("PK Population")
n   <- c(122)
m   <- c(0.6572)
sp  <- c(0.0707)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  PK Population  122  0.657  0.781  0.517  0.797

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 21 outcome measures, including the primary population pharmacokinetic outcome and clinical measures related to ophthalmologic diagnoses, treatment, retinopathy of prematurity, and neurodevelopmental impairment or death. When a study assesses multiple outcomes or comparisons, the chance of at least one apparently unusual result can increase if each is tested independently. General statistical note: multiplicity procedures can address that issue, but the registry record does not report whether any adjustment was planned or applied.

The registry contains no analysis entries. It does not report a statistical analysis plan, a hierarchy among secondary outcomes, or the tests used for the listed clinical outcomes. It is therefore not possible to determine which comparisons were prespecified, how the analysis controlled for multiple testing, or whether outcome reporting reflects all analyses conducted.

Missing-data methods are not reported in the registry record. The record describes sampling times and a follow-up examination, but does not give the amount of missing outcome data, reasons for missingness, imputation procedures, or sensitivity analyses. The one infant assigned to placebo who received low-dose inositol is described separately: the infant was included with low dose for pharmacokinetics and as randomized for other analyses. No broader analysis-population definitions are reported.

These omissions limit assessment of the robustness and completeness of the outcome analyses. They do not show that a particular method was absent from the investigators’ work; they mean that the method is not reported in 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: anemia (37.1%), apnea (32.1%), delayed gastric emptying (23.3%), poor perfusion or hypotension (22.9%), thrombocytosis (14.3%).

The safety record lists four groups. For serious adverse events, 17 of 29 participants in the low-volume inositol group, 20 of 30 in the mid-level group, 17 of 28 in the high-volume group, and 28 of 35 in the placebo group were affected. For other adverse events, the corresponding counts were 24 of 29, 20 of 30, 19 of 28, and 24 of 35. Death counts were 2, 5, 1, and 6, respectively. These are reported counts, not adjusted comparisons.

The most frequently listed serious adverse event terms are anemia (37.1%), apnea (32.1%), delayed gastric emptying (23.3%), poor perfusion or hypotension (22.9%), thrombocytosis (14.3%), and hyperglycemia (11.4%). The registry record does not explain the denominator or calculation basis for these term percentages, so they should be read as reported rather than used to infer group-specific risk.

Serious-event and other-event counts do not show severity, timing, recurrence, or causal relationship to treatment. The registry record does not report statistical tests or uncertainty intervals for these safety summaries. Differences in counts across groups should therefore be treated descriptively, not as proof of a treatment effect or its absence.

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

The registry record documents a randomized, placebo-controlled study of three inositol dose levels in premature infants, with a primary focus on population pharmacokinetics and additional safety and clinical outcomes. It identifies the primary measure as mean pharmacokinetic volume in l/kg, with standard error, and describes repeated blood sampling over 10 weeks. It also provides group-level adverse-event and death counts.

The record does not report the numerical primary outcome estimate or its uncertainty. It also does not provide numerical results for the listed clinical outcomes, statistical comparisons, or analysis details. As a result, it cannot support a conclusion about the size or precision of any pharmacokinetic difference, or whether clinical outcomes differed between dose groups and placebo.

The study rationale proposes that maintaining inositol concentrations similar to those occurring naturally in utero might reduce retinopathy of prematurity and bronchopulmonary dysplasia. That is the rationale described in the registry, not a result. Pharmacokinetic characterization can inform understanding of drug disposition, but it is distinct from evidence about clinical outcomes.

In general, a non-significant test would not by itself demonstrate equivalence, and a difference in observed counts would not by itself establish causation. Here, the registry record does not report the tests or estimates needed to make either kind of inference. The reported safety figures describe participants affected in the listed groups, without adjusted comparisons or uncertainty estimates.

Accordingly, the most defensible interpretation is limited to the study structure, endpoint definition, sampling plan, analysis-population note, and descriptive safety counts. The registry record does not establish that inositol did or did not alter pharmacokinetics, retinopathy of prematurity, bronchopulmonary dysplasia, or later neurodevelopment.

14. Why This Trial Matters Statistically

This trial illustrates why the endpoint and the clinical question must be distinguished. Its primary outcome is a pharmacokinetic parameter, whereas its rationale concerns possible clinical outcomes in premature infants. A pharmacokinetic estimate can describe drug disposition, but it does not directly answer whether a clinical condition or later outcome changed.

The design also highlights the importance of analysis population. One infant was randomized to placebo but received the low dose, and the record assigns this infant differently for pharmacokinetic and other analyses. Readers need to know whether results are organized by randomized group or by received treatment because those approaches address different estimands and can have different vulnerabilities.

Repeated sampling creates another interpretive issue: a population pharmacokinetic estimate depends on the data collected over time and on the model used to characterize those measurements. The registry describes the sampling schedule but does not report the model or the estimate. Thus, the design can be understood more fully than its primary result can be evaluated.

Finally, the record lists many outcome measures but no analysis entries. This makes transparency about outcome definitions, missing data, multiplicity, and statistical methods especially relevant. The case demonstrates that a completed trial record may document its design and safety counts while leaving key elements needed to assess the precision and robustness of treatment comparisons 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.

The main limitation for interpreting results is that the registry record does not report a numerical result for the primary pharmacokinetic outcome. It identifies the measure, unit, summary statistic, and sampling schedule, but gives no mean estimate, standard error, confidence interval, or dose-group comparison. Clinical outcome results and statistical analyses are also not reported in the registry record.

Methods details are limited. The model used for population pharmacokinetics, analysis assumptions, missing-data handling, interim analyses, multiplicity approach, and statistical analysis plan are not reported. The record lists 21 outcome measures and no analysis entries, leaving the relationship between planned and reported analyses unclear.

The enrollment information has two forms: listed enrollment is 125, while the brief description gives an estimated enrollment of 96. The record does not explain the difference. The official title says double-masked, whereas the registry masking classification is quadruple; operational details that might clarify the distinction are not reported.

For the safety summaries, the record gives counts but not inferential comparisons, uncertainty intervals, event timing, or causal attribution. It also does not explain the denominator for the percentages attached to the leading serious adverse event terms. These limits do not invalidate the descriptive information, but restrict conclusions that can be drawn from it.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Multi-dose Pharmacokinetics and Dose Ranging of Inositol in Premature Infants (INS-2) — NCT01030575.
• Registry record last updated 2022-06-14; status last verified 2022-03.
• Results first posted 2021-03-12.
• 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

NCT01030575 is a completed Phase II randomized, placebo-controlled, parallel-group study of multiple doses of inositol in premature infants. The groups received 10 mg/kg/day, 40 mg/kg/day, or 80 mg/kg/day of 5% inositol, or 5% glucose placebo. Listed enrollment is 125; the brief description gives an estimated enrollment of 96. The study start is recorded as 2010-01 and primary completion as 2011-05.

The primary outcome is population pharmacokinetic volume, measured in l/kg and summarized as a mean with standard error. The record describes repeated blood sampling over 10 weeks but does not report a numerical primary result. It lists 21 outcome measures and no analysis entries. Safety information includes counts of participants with serious and other adverse events and deaths in each group. Numerical clinical outcome analyses, missing-data methods, multiplicity procedures, and further statistical-plan details are not reported in the registry record.