Tmax: An Unconfounded Metric for Rate of Absorption in Single Dose Bioequivalence Studies
Abstract
Purpose While peak drug concentration (Cmax) is recognized to be contaminated by the extent of absorption, it has long served as the indicator of change in absorption rate in bioequivalence studies. This concentration measure per se is a measure of extreme drug exposure, not absorption rate. This paper redirects attention to Tmax as the absorption rate variable.Methods We show that the time to peak measure (Tmax), if obtained from equally spaced sampling times during the suspected absorption phase, defines a count process which encapsulates the rate of absorption. Furthermore such count data appear to follow the single parameter Poisson distribution which characterizes the rate of many a discrete process, and which therefore supplies the proper theoretical basis to compare two or more formulations for differences in the rate of absorption. This paper urges limiting the use of peak height measures based on Cmax to evaluate only for dose-dumping, a legitimate safety concern with any formulation. These principles and techniques are illustrated by a bioequivalence study in which two test suspensions are compared to a reference formulation.Results Appropriate statistical evaluation of absorption rate via Tmax supports bioequivalence, whereas the customary analysis with Cmax leads to rejection of bioequivalence. This suggests that the inappropriate use of Cmax as a surrogate metric for absorption rate contributes to the unpredictable and uncertain outcome in bioequivalence evaluation today.
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The rate of absorption can be profoundly affected by the drug formulation and route of administration.
“The rate of absorption can be profoundly affected by the drug formulation and route of administration [16, 17], which has implications for the onset and duration of action for oral and LAI antipsychotics.”
From Pharmacokinetic Characteristics of Long-Acting Injectable Antipsychotics for Schizophrenia: An Overview (2021) · cites this paper as [17]
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- Authors
- Basson, R. P., Cerimele, B. J., DeSante, K. A., & Howey, D. C.
- Affiliations
- Eli Lilly (United States) (US)
- Venue
- Pharmaceutical Research
- Published
- 1996-02
- Volume
- 13
- Issue
- 2
- Pages
- 324-328
- ISSN
- 0724-8741 (ISSN-L)
- 1573-904X
- OpenAlex
- W1563687119
- Cited by
- 22
- References
- 13
- Citations by year
- 2024: 2 · 2023: 2 · 2022: 1 · 2021: 1 · 2018: 1 · 2016: 2 · 2013: 1 · 2012: 3
- FWCI
- 0.81
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- Locations
- Pharmaceutical Research (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Health Sciences › Medicine › Pediatrics, Perinatology and Child Health › Pharmaceutical studies and practices
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Drug Solubulity and Delivery Systems
- Keywords
- Tmax, time to peak concentration, bioequivalence, Cmax, counting processes, Poisson distribution, dose dumping, pharmacokinetics
- MeSH terms
- Absorption, Adult, Anti-Bacterial Agents, Chemistry, Pharmaceutical, Drug Administration Schedule, Humans, Male, Pharmacokinetics, Therapeutic Equivalency, Cross-Over Studies
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