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 Effect of Weight and/or Obesity on Sulfamethoxazole and Trimethoprim Concentrations (NCT01167452), a na phase 4 study. The primary outcome is Elimination Rate Constants for Sulfamethoxazole and Trimethoprim.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01167452 |
| Phase | Phase 4 |
| Condition | Obesity, Pharmacokinetics, MRSA |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 36 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Texas Tech University Health Sciences Center |
| Results posted | Yes |
2. Clinical Question
Population
Volunteers described in the official title as normal weight, overweight, and obese. BMI groups were used for recruitment purposes, not for ordinal data analysis. Other participant characteristics are not reported in the registry record.
Intervention
Participants received sulfamethoxazole/trimethoprim, described as 2 DS tablets containing 1600 mg/320 mg.
Comparator
No comparator group is identified. The record describes a single-group study, so it does not support a like-for-like comparison between treatment groups.
Primary question
The study examined elimination rate constants for sulfamethoxazole and trimethoprim over 24 hours, in the context of the effect of weight and obesity on concentrations of the drugs. The numerical endpoint results are not reported in the registry record.
The clinical question is pharmacokinetic: how the drugs’ concentrations change over time after administration, and whether weight-related characteristics may be relevant to those patterns. The registry description frames the study around dosing across body weights, while the stated primary outcome is an elimination rate constant for each drug. Such a constant describes the rate at which a drug is eliminated under the conditions being studied; it is not itself a direct measure of clinical benefit or harm.
The record says the entire cohort was analyzed for study outcomes and that BMI groups were for recruitment purposes only. It therefore does not describe a primary analysis comparing outcomes across BMI categories. The record also does not report concentration values, estimated rate constants, or an association between weight and either drug’s pharmacokinetics. The question can be identified from the study description, but the posted record does not provide the numerical results needed to assess the observed pattern or its precision.
3. Trial Design
This is a Phase 4, completed, single-group study sponsored by Texas Tech University Health Sciences Center. The registry reports an enrollment of 36. Study start is recorded as 2010-07 and primary completion as 2012-05. Allocation is listed as not applicable, and masking is listed as none. These features describe a study without randomized allocation to separate treatment groups and without masking.
The intervention is sulfamethoxazole/trimethoprim. The arm description specifies 2 DS tablets containing 1600 mg/320 mg. The design is not a controlled comparison: the registry identifies a single group, and the record does not describe an untreated or alternative-treatment group. Accordingly, the design can describe pharmacokinetic observations under the study conditions, but it does not establish a treatment contrast against a concurrent control.
The official title describes normal-weight, overweight, and obese volunteers. The brief summary clarifies that BMI groups were used for recruitment, not for ordinal data analysis, and says the entire cohort was analyzed for study outcomes. This means the registry does not describe an analysis that treats those BMI groups as an ordered exposure or reports group-specific comparisons. More detailed eligibility criteria, recruitment procedures, participant characteristics, administration schedule beyond the arm description, and blood-sampling schedule are not reported in the registry record.
The primary outcome is elimination rate constants for sulfamethoxazole and trimethoprim, with a 24-hour timeframe and median as the summary measure, accompanied by the full range. The record lists one outcome measure and two analyses, but does not specify the analysis procedures or report numerical estimates. The study is marked completed; completion status alone does not supply the missing outcome estimates or determine how precisely the study addressed its pharmacokinetic question.
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 | Sulfamethoxazole/Trimethoprim |
|---|---|
| STARTED | 36 |
| COMPLETED | 36 |
| NOT COMPLETED | 0 |
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 | Sulfamethoxazole/Trimethoprim |
|---|---|---|
| Participants analysed | 36 | |
| Age, Categorical: <=18 years | Participants | 1 |
| Age, Categorical: Between 18 and 65 years | Participants | 34 |
| Age, Categorical: >=65 years | Participants | 1 |
| Age, Continuous | years | 37 (18 to 77) |
| Sex: Female, Male: Female | Participants | 18 |
| Sex: Female, Male: Male | Participants | 18 |
| Region of Enrollment: United States | participants | 36 |
6. Primary Endpoint
The registry lists the primary outcome as Elimination Rate Constants for Sulfamethoxazole and Trimethoprim, measured over 24 hours.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | hr-1 |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “Elimination Rate Constants for Sulfamethoxazole and Trimethoprim.” It concerns the elimination of each drug over a 24-hour timeframe. In general, an elimination rate constant represents how quickly drug concentration declines through elimination under the conditions of a pharmacokinetic study. It is a description of drug disposition, rather than a direct measure of a patient-centered clinical outcome.
The registry specifies the median and full range as the endpoint summary. The median describes the middle of the observed values and is less influenced by extreme observations than the arithmetic mean. The full range gives the lowest and highest observed values, but does not show how values are distributed between those endpoints. These summaries can be useful when observations are skewed or when a small study makes the shape of the data important to inspect. General statistical interpretation should still consider the underlying distribution and the amount of data available.
A rate constant can help characterize pharmacokinetic behavior and can be relevant to questions about drug exposure. However, a rate constant alone does not establish whether a dose is appropriate for a particular person, nor does it directly establish efficacy or safety. The registry record does not report the actual medians, full ranges, units beyond hr-1, or concentration measurements. It also does not report an estimated relationship between weight and the endpoint. The reason for selecting this endpoint beyond its stated pharmacokinetic focus is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a pharmacokinetic study of sulfamethoxazole and trimethoprim in volunteers recruited across weight categories. Its primary endpoint is the median elimination rate constant for each drug, with the full range, over 24 hours. Yet numerical endpoint estimates are not reported in the registry record. Without those values, the observed rate constants, the range of participant-level results, and the size or direction of any weight-related pattern cannot be assessed from this record.
The record says the entire cohort was analyzed for study outcomes, while BMI groups were used only for recruitment and not for ordinal data analysis. This description does not establish that the outcome was compared across weight categories. It would therefore be inappropriate to read the study title as evidence that a particular category had a higher or lower rate constant, or that the study estimated a dose adjustment by weight. No such result is reported in the registry record.
Precision also cannot be evaluated from the posted endpoint description. A confidence interval would indicate the range of values compatible with the data under the analysis assumptions, and would help distinguish a relatively precise estimate from one with substantial uncertainty. No confidence interval, standard error, or other measure of inferential precision is reported in the registry record. The full range is a descriptive spread of observed values, not a confidence interval for the median.
The study has no listed comparator group and is identified as single-group with allocation not applicable. Thus, its design does not provide a randomized treatment comparison. Pharmacokinetic observations within a single group may describe what was measured after administration, but they cannot by themselves separate an effect of weight from other explanations or show a comparative treatment effect.
The record lists two analyses for the outcome, but does not describe their estimands, statistical models, covariates, or inferential procedures. It is not possible to determine whether the analyses were exploratory or confirmatory, how they related to each other, or whether uncertainty was adjusted for multiple analyses. The available information supports describing the study question and design, but not drawing a numerical conclusion about the size, direction, or precision of the pharmacokinetic findings.
9. Statistical Methods Explained
The registry gives a limited description of the statistical methods. It identifies the primary outcome as elimination rate constants for sulfamethoxazole and trimethoprim, summarized by the median and full range over 24 hours. It also states that BMI groups were used for recruitment purposes only and were not used for ordinal data analysis. The entire cohort was analyzed for study outcomes. The detailed statistical analysis plan, model specification, handling of repeated observations, and inferential methods are not reported in the registry record.
What does a median and full range describe?
In general, the median is the central value when observations are ordered. It can be a useful summary when data are asymmetric or include unusually high or low observations, because the median is less sensitive to extremes than the mean. The full range describes the observed minimum and maximum. It communicates the outer spread, but it does not show where most observations lie, whether there are clusters, or how much uncertainty surrounds the median. A range is a descriptive summary of the observed data and should not be interpreted as an interval estimate for the underlying population value.
For this endpoint, the registry says that the median and full range were used. It does not provide the actual values. The record therefore does not allow readers to assess skewness, unusual observations, or the extent of participant-to-participant variation. Nor does the listing say whether any additional summaries or graphical checks were used.
What does an elimination rate constant represent?
In general, a pharmacokinetic elimination rate constant characterizes the rate of drug elimination within a specified model and set of study conditions. Interpreting it depends on how samples were collected, how concentrations were measured, and how the model represented the concentration-time profile. These procedural and modelling details are not reported in the registry record. A rate constant should not be treated as a direct measure of clinical outcome, and its meaning does not by itself establish a dosing recommendation.
The timeframe is recorded as 24 hours. The registry does not describe the timing or number of blood draws within that interval, the treatment of concentrations below assay limits, or the pharmacokinetic model used to obtain the constants. Those details matter because estimates can depend on the observed portion of the concentration-time profile and on modelling assumptions.
How should the analysis population be understood?
The brief summary says the entire cohort was analyzed for study outcomes. This describes the intended analysis population in broad terms, but does not establish that every enrolled participant contributed complete data to every endpoint or analysis. The number included in each analysis, exclusions, incomplete observations, and reasons for missing measurements are not reported in the registry record.
The summary also states that BMI groups were for recruitment purposes and were not used for ordinal data analysis. In general, an ordinal analysis would use an ordering among categories as part of the statistical model. The registry’s statement indicates that this was not the stated approach for these groups. It does not, however, identify another model for weight or BMI, nor does it state whether these characteristics were entered as continuous variables or used in any other analysis.
What can be inferred from the listed analyses?
The record lists two analyses, but does not describe their separate aims or methods. A count of analyses does not reveal whether they represent separate drugs, alternative models, or another distinction. The model, covariates, assumptions, hypothesis tests, confidence intervals, and decision criteria are not reported in the registry record. Consequently, the numerical analysis cannot be reproduced or critically assessed from the registry description alone.
In general, pharmacokinetic observations collected over time may be correlated within a participant. Statistical methods should account for that dependence when appropriate rather than treating every measurement as independent. The registry does not state how repeated measurements were handled. Over-dispersion, in general, means that observed variability exceeds what a chosen statistical model expects; when present, it can make model-based uncertainty too small if ignored. Whether over-dispersion was relevant or assessed in this study is not reported in the registry record.
The record also gives planning assumptions for sample-size illustrations: two-sided significance level 0.05, equal allocation between two hypothetical arms, and a normal approximation, with effects expressed as fractions of the observed effect. These are described as planning illustrations based on the observed effect, not as the trial’s own design. The actual study is single-group, so the hypothetical equal-allocation assumption should not be mistaken for its design. No sample-size illustration values are reported in the registry record. Such planning calculations are not observed power and cannot replace an estimate of the uncertainty around the study’s own results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and two analyses. It does not explain how the analyses relate to one another, whether they were specified before data collection, or whether either analysis was designated as primary for inference. The statistical plan for handling multiple analyses, including any adjustment to control the chance of false-positive findings, is not reported in the registry record. It is therefore not possible to assess the implications of multiplicity from the description alone.
Missing-data procedures are also not reported in the registry record. The brief summary says the entire cohort was analyzed for study outcomes, but this does not state how many participants contributed usable data to each analysis, whether all planned concentration measurements were available, or how incomplete observations were handled. The registry does not report reasons for missing data, imputation procedures, or sensitivity analyses. In general, missing measurements can affect an estimate if the probability of missingness is related to participant characteristics or outcomes; the available record does not permit assessment of that possibility.
The record does not provide a detailed analysis-population definition, such as endpoint-specific inclusion criteria. It also does not state whether exclusions were made after enrollment or how such exclusions were treated. The broad statement that the entire cohort was analyzed should be read as a description in the summary, not as evidence that every enrolled participant had complete data in every analysis.
Finally, BMI groups were used for recruitment and not for ordinal data analysis. The registry does not report whether BMI or another measure of weight was analyzed in a different form. These omissions limit interpretation of how the study addressed its stated interest in weight and pharmacokinetics.
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 |
|---|---|---|---|
| Sulfamethoxazole/Trimethoprim | 0 | 36 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 2% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Sulfamethoxazole/Trimethoprim | 4 of 36 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Sulfamethoxazole/Trimethoprim |
|---|---|---|
| Headache | Nervous system disorders | 3 of 36 |
| Fainting | Nervous system disorders | 1 of 36 |
The registry reports serious adverse events for the sulfamethoxazole/trimethoprim group as 0 of 36 participants affected, with 36 at risk. It reports other adverse events as 4 of 36 participants affected, with 36 at risk. The record does not identify the types of the other adverse events in the information, so their nature, severity, timing, and relationship to study medication cannot be characterized.
These figures are counts recorded for the study group, not a comparison between treatments. With no comparator group, they do not estimate a relative difference in adverse events versus another intervention or versus no intervention. They also do not establish that an event was caused by the study medication. The registry does not provide further details about event definitions, monitoring procedures, or how attribution was assessed.
Deaths are not reported in the registry record. The serious adverse event count and the other adverse event count are distinct registry categories; the available record does not provide event-level detail with which to examine overlap or timing. These safety figures should therefore be read as limited descriptive reporting, not as a complete characterization of safety.
12. What the Result Does, and Does Not, Mean
This study addresses a relevant pharmacokinetic question: whether weight-related characteristics may be associated with how sulfamethoxazole and trimethoprim are eliminated. The record identifies a defined primary outcome and describes a single-group study in volunteers recruited across weight categories. That information helps clarify what the investigators intended to examine.
The record does not report the median elimination rate constants or their full ranges. It also does not report concentration values, a numerical relationship between weight and drug elimination, or precision estimates. As a result, the posted information does not establish the direction or magnitude of an observed association, how variable the observations were, or how compatible the findings are with other possible values. It cannot support a conclusion that a weight-based dosing approach is or is not warranted.
The design also limits what can be concluded. There is no listed comparator group, and the BMI groups were for recruitment rather than ordinal data analysis. A single-group pharmacokinetic study can describe measurements made under its conditions, but it does not provide a randomized comparison and cannot by itself establish causal effects of body weight or compare treatment strategies.
Elimination rate constants are pharmacokinetic measures, not direct clinical outcomes. Even if numerical estimates were available, interpreting their clinical implications would require attention to the study methods, uncertainty, drug exposure, and clinical context. Those further details are not reported in the registry record. The completed status and enrollment description do not substitute for outcome results. The strongest interpretation supported by the record is that the study was designed to characterize drug elimination in a volunteer cohort; its numerical findings and their precision are not available in the registry record.
13. Why This Trial Matters Statistically
This study is statistically interesting because it links a practical question about weight and drug dosing to a measurable pharmacokinetic endpoint. Elimination rate constants offer a way to describe drug disposition, while a median and full range can communicate a central observation and the observed spread without assuming that the data are well represented by a mean alone.
The design information is equally important. A single-group study and a recruitment approach spanning weight categories are not the same as a planned comparative analysis across those categories. The registry explicitly says BMI groups were not used for ordinal data analysis. That distinction prevents readers from assuming that the study estimated a trend across categories merely because the categories appear in the official title.
The record also illustrates why endpoint definitions and results need to be considered together. Naming the measure and summary statistic does not show the observed values, their uncertainty, or the analysis used to produce them. Without numerical estimates and methods, readers cannot judge whether the data were precise, whether the pattern was consistent, or how the findings relate to the study question.
Finally, the safety reporting is descriptive and lacks a comparator. Adverse-event counts can provide useful context, but without event details and comparative data they do not answer broader questions about relative safety. The study’s statistical contribution cannot be fully assessed from the registry description because its endpoint results and detailed analysis methods are not reported in the registry record.
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.
A central limitation for interpretation is that the registry record does not report numerical results for the primary endpoint. The median elimination rate constants and full ranges are not available, and neither are confidence intervals or other measures of precision. Without these, readers cannot assess the magnitude, variability, or uncertainty of the pharmacokinetic observations.
The design is single-group, with allocation listed as not applicable and no masking. No comparator is described, so the record does not support a treatment-group contrast. Although the official title refers to normal-weight, overweight, and obese volunteers, the brief summary says BMI groups were for recruitment and were not used for ordinal data analysis. The registry does not report another specific analysis of weight or BMI.
Methodological details that would help interpret the endpoint are also absent. Sampling times, assay details, the pharmacokinetic model, covariates, missing-data handling, and analysis-specific participant counts are not reported in the registry record. The record lists two analyses but does not explain their aims or methods, and it does not describe any multiplicity procedure.
The adverse-event reporting is limited to aggregate counts. Event types and other details are not reported in the registry record, and the figures are not comparative. Deaths are not reported in the registry record. Enrollment and completed status describe the study’s scale and status, but do not resolve these limitations or supply the missing outcome information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Effect of Weight and/or Obesity on Sulfamethoxazole and Trimethoprim Concentrations — NCT01167452.
- Registry record last updated 2017-06-14; status last verified 2017-05.
- Results first posted 2016-11-02.
- 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
The registry describes a completed Phase 4, single-group study sponsored by Texas Tech University Health Sciences Center, with enrollment of 36. The study examined sulfamethoxazole/trimethoprim in volunteers described in the official title as normal weight, overweight, and obese. The intervention description specifies 2 DS tablets containing 1600 mg/320 mg.
The primary outcome was elimination rate constants for sulfamethoxazole and trimethoprim over 24 hours, summarized by median and full range. BMI groups were used for recruitment rather than ordinal data analysis, and the brief summary says the entire cohort was analyzed for outcomes. The record lists two analyses but does not describe their methods or provide numerical endpoint results.
The registry reports 0 of 36 participants with serious adverse events and 4 of 36 with other adverse events. Event details and deaths are not reported in the registry record. The single-group design and absence of numerical pharmacokinetic results limit interpretation of the study’s findings.