This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Study of AzaSite Versus Vigamox Concentrations in the Conjunctiva and Aqueous Humor in Subjects Undergoing Routine Cataract Surgery (NCT00575380), a randomized phase 4 study. The primary outcome is Conjunctiva Concentration Prior to Cataract Surgery at One of Ten Time Points Ranging From 1 to 14 Days (Per Protocol Pharmacokinetic Population).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00575380 |
| Phase | Phase 4 |
| Condition | Bacterial Infections, Eye Infections, Cataract Extraction |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 116 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Merck Sharp & Dohme LLC |
| Results posted | Yes |
2. Clinical Question
Population
Participants were undergoing routine cataract surgery. The study enrolled 116 participants, and the primary outcome names a per-protocol pharmacokinetic population. Further details about eligibility criteria and the characteristics of the analyzed population are not reported in the registry record.
Intervention
AzaSite eye drops were given as one drop two times a day for two days and once a day for the next five days. The study evaluated concentrations of the drug in conjunctiva and aqueous humor before cataract surgery at scheduled times after administration began.
Comparator
Vigamox eye drops were given as one drop three times a day for seven days. As with AzaSite, drug concentrations were to be evaluated in conjunctiva and aqueous humor before surgery. The dosing schedules were not identical.
Primary question
The primary outcome was conjunctiva concentration before cataract surgery, measured at one of ten scheduled time points ranging from 1 to 14 days. The registry record also lists aqueous humor concentration as a secondary outcome. The outcome values and direct comparisons between the treatments are not reported in the registry record.
3. Trial Design
This was a Phase 4, randomized, open-label, parallel-group study. The registry record describes it as multicenter and gives the enrollment as 116. Participants were assigned to AzaSite eye drops or Vigamox eye drops; masking was listed as none. The study was completed, with a start date of 2007-12 and primary completion in 2008-06.
The treatment schedules differed. AzaSite was administered as one drop two times a day for two days and once a day for the next five days. Vigamox was administered as one drop three times a day for seven days. These details matter when interpreting concentration measurements: the time since the first administration and the pattern of repeated dosing are relevant context for a pharmacokinetic measurement. The registry record does not describe additional protocol details about dose administration or adherence.
The primary outcome concerned conjunctiva concentration before cataract surgery, measured at one of ten scheduled time points ranging from 1 to 14 days. Its time frame lists nominal hours relative to the first eye drop. The listed schedules are Az(hr): 1,12,48,49,72,144,145,168,216,312 and Vig(hr): 1,8,48,49,56,144,145,168,216,312. Aqueous humor concentration before surgery at one of ten time points is listed as a secondary outcome.
The registry record does not report how participants were assigned to particular sampling times, whether allocation was concealed, or the number assigned to each treatment in the outcome population. It lists 58 participants at risk for adverse-event reporting in each treatment group, but those figures do not establish the analyzed sample size for either concentration outcome. Details of the randomization procedure and the study’s sample-size justification 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
| Stage | Azasite | Vigamox |
|---|---|---|
| STARTED | 58 | 58 |
| COMPLETED | 57 | 55 |
| NOT COMPLETED | 1 | 3 |
Reasons for not completing this period:
| Reason | Azasite | Vigamox |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
| Adverse Event | 0 | 1 |
| Various | 0 | 2 |
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.
| Characteristic | Unit | Azasite | Vigamox | Total |
|---|---|---|---|---|
| Participants analysed | 58 | 58 | 116 | |
| Age Continuous | years | 71.0 (SD 7.57) | 66.3 (SD 10.02) | 68.6 (SD 9.15) |
| Sex: Female, Male: Female | Participants | 34 | 28 | 62 |
| Sex: Female, Male: Male | Participants | 24 | 30 | 54 |
6. Primary Endpoint
The registry lists the primary outcome as Conjunctiva Concentration Prior to Cataract Surgery at One of Ten Time Points Ranging From 1 to 14 Days (Per Protocol Pharmacokinetic Population), measured over Az(hr): 1,12,48,49,72,144,145,168,216,312; Vig(hr): 1,8,48,49,56,144,145,168,216,312.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | ug/g |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was conjunctiva concentration before cataract surgery. Concentration is a continuous measurement, and the registry record specifies that the outcome was to be expressed as a mean with standard deviation in ug/g. It describes the nominal measurement time as scheduled time relative to administration of the first eye drop.
Concentration in conjunctiva is relevant to the study’s pharmacokinetic question because it describes the amount of drug measured in that tissue after administration. Measurements at different scheduled times can characterize how concentrations vary with time. This is a general explanation of the role of a pharmacokinetic endpoint; it does not establish what the measurements in this trial showed.
The endpoint was planned at one of ten time points ranging from 1 to 14 days, rather than as a single measurement at one common time. The listed hourly schedules differ between the arms at some time points. That timing context is important for any comparison: a concentration is interpretable in relation to when it was measured and the dosing schedule preceding measurement.
The registry record describes the endpoint but does not report the mean concentrations, standard deviations, participant counts contributing to each time point, or treatment comparisons. It therefore does not permit a numerical assessment of the observed conjunctiva concentrations or their precision. Aqueous humor concentration was a separate secondary outcome, not the primary endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study’s question and design but does not report concentration values or statistical comparisons. Although it identifies conjunctiva concentration as the primary outcome and aqueous humor concentration as a secondary outcome, it contains no outcome estimates in the registry record recorded for these outcomes. The direction, size, and precision of any difference between AzaSite and Vigamox therefore cannot be described from the registry record.
The primary outcome was a continuous measure summarized as a mean and standard deviation. Those summary statistics would describe the concentration measurements within the relevant treatment and time groups. To assess a treatment contrast, readers would also need a clearly defined comparison, the number of participants contributing data, and an estimate of uncertainty. These outcome details are not reported in the registry record. No confidence intervals or p-values for the concentration outcomes are reported in the registry record.
Time is central to interpretation. The primary outcome was scheduled at one of ten time points, and the record lists nominal hours from the first eye drop. The listed schedules are not identical for the two treatments at every time point. Concentration values taken at different times after starting administration should not be treated as if they were measurements at a single shared time. The registry record does not report a time-specific comparison or an overall treatment effect across time points.
The study was randomized, which describes how assignment to treatments was intended to occur, but randomization alone does not supply the missing outcome estimates. The trial was open-label, and masking was listed as none. The registry record does not report whether knowledge of assignment could have influenced sample collection, laboratory measurement, or other aspects of the outcome assessment. No conclusion about the impact of those possibilities can be drawn from the record.
The adverse-event figures are separate from the pharmacokinetic outcomes. The record lists no serious adverse events in either group, and lists other adverse events affecting 3 participants in the AzaSite group and 2 in the Vigamox group. Those counts do not substitute for concentration data and do not establish comparative safety. The record does not report the concentration outcome findings needed to answer the study’s primary statistical question.
Accordingly, the posted information supports a description of the planned concentration outcomes, dosing schedules, and study design, but not a conclusion about which treatment had higher or lower concentrations, whether the treatments differed, or how precise any difference was. Such findings are not reported in the registry record.
9. Statistical Methods Explained
The registry record identifies a randomized, open-label, parallel-group study and defines the primary endpoint as conjunctiva concentration before cataract surgery. The endpoint is continuous and is specified to be expressed as a mean with standard deviation. These details identify the measurement and intended descriptive summary, but they do not provide a complete statistical analysis plan. The registry record does not report the methods used to compare treatment groups, the outcome estimates, or the uncertainty around those estimates.
What does a mean and standard deviation describe?
In general, the mean is a measure of the center of a set of numerical observations. The standard deviation describes how spread out the observations are around that mean. For a concentration outcome, these summaries can describe measurements within a treatment group and a scheduled sampling time. They are not, by themselves, a treatment comparison. A comparison also needs a specified contrast between groups and information about its uncertainty. The registry record does not report the concentration means or standard deviations for this trial.
Why does measurement time matter?
The primary outcome was scheduled at one of ten time points ranging from 1 to 14 days. The record gives nominal hours relative to administration of the first eye drop and lists the time schedules separately for the two treatments. This is important because concentration is interpreted in relation to the time since administration and the preceding dosing pattern. The AzaSite and Vigamox schedules differ, and some of their listed nominal sampling times differ as well. A comparison should therefore be understood in the context of the time point and treatment schedule, rather than treated as an unspecified single measurement.
The registry record does not explain whether each participant contributed a measurement at only one scheduled time or how participants were distributed among time points. It also does not describe a model that accounts for time, repeated observations, or potential differences in the number of observations across times. Those methods are not reported in the registry record, so no particular analysis should be assumed.
How should uncertainty be understood?
In general, a confidence interval expresses the range of estimates compatible with the data and a stated statistical procedure. A narrow interval indicates greater precision than a wide interval under that procedure. A p-value addresses compatibility between observed data and a specified null hypothesis under the assumptions of a test; it does not measure the size or clinical importance of an effect. Neither confidence intervals nor p-values for the concentration outcomes are reported in the registry record. No conclusion about the precision or statistical significance of a treatment contrast can be made from the endpoint description alone.
What does randomization contribute?
In general, random assignment can support a fair comparison by reducing systematic differences between treatment groups at the point of assignment, subject to the conduct and analysis of the study. The registry record says the study was randomized but does not report the randomization sequence method, allocation concealment, or the method used to analyze the assigned groups. The record also identifies the primary outcome population as per-protocol, but does not give the population’s size or define the criteria used to determine per-protocol inclusion. The effect of any exclusions cannot be assessed from the information reported.
What can be said about planning calculations?
The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect and that non-time-to-event planning figures are participants per arm. These are planning assumptions, not evidence of power achieved in the trial. The numerical planning results and the effect estimates on which they depend are not reported in the registry record. The trial’s own sample-size justification is also not reported in the registry record. A planning illustration must not be read as observed power or as a result from participants’ outcomes.
More generally, statistical methods should be interpreted in light of the endpoint, analysis population, timing, and missing observations. The registry record does not report a comparison model, a missing-data method, an interim analysis plan, or a multiplicity procedure. These omissions limit what can be inferred about the intended handling of multiple sampling times and outcomes. They do not imply that a particular method was or was not used outside the information in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The primary concentration outcome was scheduled at one of ten time points, and aqueous humor concentration was listed as a secondary outcome. Examining multiple outcomes or time-specific comparisons can raise a multiplicity question: in general, when several statistical hypotheses are tested, the chance of at least one apparently unusual result may increase unless the analysis plan addresses that issue. This general concern does not establish that multiple tests were performed in this trial.
A multiplicity procedure, a prespecified hierarchy among outcomes, or another approach to interpreting multiple comparisons is not reported in the registry record. The record also does not report a set of outcome test results or p-values, so the number and nature of any comparisons actually conducted cannot be assessed from the registry information.
The primary outcome names a per-protocol pharmacokinetic population. The registry record does not provide the population’s definition, the number analyzed at each time point, or a participant flow for the concentration outcomes. It also does not describe an intention-to-treat analysis or a comparison between analysis populations. The adverse-event groups each list 58 participants at risk, but those figures should not be assumed to represent the analysis population for the pharmacokinetic endpoints.
Missing-data amounts, reasons for missing measurements, and methods for handling missing concentration values are not reported in the registry record. In general, missingness can affect the interpretation of estimates if participants with observed measurements differ from those whose measurements are unavailable. Without counts and methods, the direction or extent of any such effect cannot be assessed. The registry record also does not report interim analyses or stopping rules.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Azasite | 0 | 58 | 0.0% |
| Vigamox | 0 | 58 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Azasite | 3 of 58 |
| Vigamox | 2 of 58 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Azasite | Vigamox |
|---|---|---|---|
| Intraocular pressure increased | Investigations | 3 of 58 | 2 of 58 |
The registry record lists serious adverse events for 58 participants at risk in the AzaSite group and 58 in the Vigamox group. It records 0 serious adverse events in each group. These are event counts as recorded; the record does not list serious adverse-event terms. The figures do not establish that no other safety outcomes occurred or that the groups had equivalent safety.
For other, non-serious adverse events, the record lists 3 affected participants in the AzaSite group and 2 in the Vigamox group, with 58 participants at risk in each. These counts do not show the severity, timing, duration, or relationship of the events to treatment. The registry record does not provide event terms for these non-serious events in the information recorded here, so their clinical meaning cannot be assessed.
Deaths are not reported in the registry record. The adverse-event counts should be read as a limited safety summary, not as a complete accounting of all harms or as a statistical comparison. They are distinct from the concentration outcomes that formed the study’s primary and secondary pharmacokinetic questions.
12. What the Result Does, and Does Not, Mean
This study was designed to compare concentrations of azithromycin, administered as AzaSite, with moxifloxacin, administered as Vigamox, in conjunctiva and aqueous humor around routine cataract surgery. Its randomized, open-label, parallel-group design and the two dosing schedules are described in the registry record. The primary outcome was conjunctiva concentration before surgery, and aqueous humor concentration was listed as a secondary outcome.
What the record does not establish is the observed concentration in either group or the size and direction of a treatment difference. It does not report the means, standard deviations, participant counts for the concentration analyses, confidence intervals, or p-values. It therefore cannot show whether concentrations differed at any scheduled time, how consistent the measurements were, or how precisely any comparison was estimated. Those outcome findings are not reported in the registry record.
The record also does not establish that any concentration difference, if one was found in an analysis not reported there, would translate into a clinical benefit or harm. Drug concentration is a pharmacokinetic measurement. Interpreting its clinical relevance would require appropriate outcome evidence and context; neither can be inferred from a design description or from the adverse-event counts alone.
The absence of a reported statistical analysis in the registry record is not evidence that the treatments produced the same concentrations. It is also not evidence that one produced higher concentrations. The appropriate interpretation is limited: the record identifies the question, measurement schedule, and treatment regimens, while the numerical answers are not reported. The listed adverse-event counts are similarly limited and do not establish comparative safety or equivalence.
Thus, the registry record supports a description of what was intended to be measured and how participants were assigned to treatments. It does not support a conclusion about concentration differences, their precision, or their clinical meaning.
13. Why This Trial Matters Statistically
Statistically, this trial illustrates why an endpoint description and a study design are not substitutes for posted outcome results. Randomization, a defined concentration endpoint, and a schedule of measurements identify the intended comparison. Without the actual concentration summaries and treatment contrasts, readers cannot estimate the size, direction, or precision of the result.
It also highlights the importance of time in pharmacokinetic comparisons. The primary endpoint was measured at one of ten time points, and the record lists scheduled hours relative to the first eye drop. The treatment regimens differed, and the schedules list some different nominal measurement times. Any interpretation of a concentration comparison would need to retain those timing details rather than collapse the endpoint into an undifferentiated measure.
The study also distinguishes a primary outcome from a secondary outcome: conjunctiva concentration was primary and aqueous humor concentration was secondary. With multiple time points and outcomes, the analysis plan for comparisons and multiplicity can affect how evidence is interpreted. Those methods are not reported in the registry record. This leaves readers unable to determine how any multiple comparisons were handled.
Finally, the registry record names a per-protocol pharmacokinetic population but does not report its size or definition. That makes it important to distinguish enrollment and adverse-event reporting counts from the population used for concentration analyses. The record’s lack of concentration findings prevents a complete statistical appraisal, but the design details still make clear what information would be needed for one: time-specific estimates, analysis counts, and measures of uncertainty.
14. 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 important limitation of the registry information is that the primary and secondary concentration results are not reported in the registry record. The record does not give concentration means, standard deviations, treatment contrasts, confidence intervals, or p-values. Without these, the magnitude, direction, and precision of the pharmacokinetic findings cannot be evaluated.
The primary outcome spans ten scheduled time points, with hourly schedules listed separately for AzaSite and Vigamox. Some nominal times differ between arms. The registry record does not report how comparisons across time were defined, whether measurements were repeated within participants, or whether an overall time-based analysis was used. This means the intended handling of the timing structure is unclear.
The endpoint population is described as per-protocol, but the record does not define that population or report its size. Participant counts contributing to each time point, exclusions, and reasons for missing measurements are not reported in the registry record. The impact of exclusions or missing data on the estimates therefore cannot be assessed.
The study was open-label and masking was listed as none. The record does not describe laboratory masking or other procedures that might affect outcome assessment. It also does not report the randomization method or allocation concealment. These details limit assessment of how the study was conducted, without establishing that any specific bias occurred.
The record does not report the statistical comparison method, multiplicity handling, interim analyses, or the trial’s sample-size justification. The adverse-event summary is also limited: it lists affected counts but provides no event terms for the serious-event group and does not report deaths. These limitations restrict conclusions about both the pharmacokinetic outcomes and the broader safety profile.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of AzaSite Versus Vigamox Concentrations in the Conjunctiva and Aqueous Humor in Subjects Undergoing Routine Cataract Surgery — NCT00575380.
- Registry record last updated 2011-09-22; status last verified 2011-09.
- Results first posted 2009-09-16.
- 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.
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18. Record Summary
NCT00575380 is a completed Phase 4, multicenter, randomized, open-label, parallel-group study of AzaSite versus Vigamox in subjects undergoing routine cataract surgery. Enrollment was 116. The study began in 2007-12 and reached primary completion in 2008-06.
The primary outcome was conjunctiva concentration before cataract surgery at one of ten scheduled time points; aqueous humor concentration was listed as a secondary outcome. AzaSite and Vigamox had different dosing schedules. The primary outcome was described as a mean with standard deviation in ug/g and named a per-protocol pharmacokinetic population.
The registry record does not report concentration outcome values, statistical comparisons, or analysis details. It lists 0 serious adverse events among 58 participants at risk in each group, and other adverse events affecting 3 participants in the AzaSite group and 2 in the Vigamox group. Deaths are not reported in the registry record.