Methodology
HalfLifeDB is an educational pharmacokinetics reference. The site is built around one narrow task: making half-life curves easier to understand while clearly separating a simplified model from medical, legal, safety, or laboratory guidance.
Model used by the calculators
Each calculator uses a first-order elimination equation: remaining amount = starting amount x (1/2)^(elapsed time / half-life). The chart displays a relative amount remaining, not a measured blood, urine, saliva, tissue, or breath concentration.
This model is useful because it shows the shape of exponential decline. It is limited because many real pharmacokinetic profiles include absorption, distribution, active metabolites, multiple compartments, nonlinear elimination, or repeated dosing.
How representative half-life values are selected
A substance can have several reported half-life values. Differences may come from dose, route, formulation, population, assay method, sampling duration, or whether the reported value describes a terminal phase, an effective half-life, a parent compound, or a metabolite.
For each profile, HalfLifeDB selects one representative value to power the educational curve. When a range or note is available in the entry, the page displays it near the calculator so readers can see that the value is not universal.
Source hierarchy
The site prefers sources that let readers inspect the pharmacokinetic context directly. Stronger references include peer-reviewed pharmacokinetic studies, official product labeling, regulatory documents, and focused pharmacokinetic reviews.
Compound databases may be included for identity and background context, but an identity record does not support the numerical value by itself. A published profile must also link to a source that discusses the selected half-life or a range that contains it. Search-result pages are not used as citations.
When only indirect evidence is available, such as animal pharmacokinetics, in vitro metabolism, postmortem toxicology, or class-level review literature, the entry remains unpublished until stronger support is found. Those sources can explain uncertainty, but they are not enough to power a public calculator presented as a human pharmacokinetic reference.
What each profile should contain
- A representative half-life value used by the calculator.
- A short pharmacokinetic summary and category context.
- Model checkpoints showing what one through five half-lives mean.
- A source that supports the selected value, plus any useful background records.
- Clear limitations explaining what the page does not answer.
What HalfLifeDB intentionally avoids
- Dosing, redosing, treatment, tapering, or medication-change advice.
- Instructions for intoxication, misuse, manufacturing, purchasing, or sourcing substances.
- Claims about impairment, safety-sensitive tasks, or fitness to drive.
- Predictions for drug testing, detection windows, or evasion.
- Personalized medical decision support.
Corrections and updates
Pages may be updated when better references are identified or when a limitation needs clearer language. Correction requests can be sent to admin@halflifedb.co with the page URL, the proposed correction, and any supporting source.
Related pages: editorial policy, sources,disclaimer, and Learning Center.