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.
When direct evidence supports a curve, HalfLifeDB selects one representative value and labels the modeled parent compound, metabolite, formulation, or pharmacokinetic phase. When the source set cannot support that selection, the profile publishes as an evidence note with no numerical input or calculator.
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 substance can publish as a source-linked evidence note. Those records can explain uncertainty, but they do not power a public calculator or enter curve comparisons and downloadable model data.
What each profile should contain
- A clear model status: a supported curve or an evidence note with no curve.
- A compound-specific pharmacokinetic summary and category context.
- For modeled profiles, checkpoints showing what one through five half-lives mean.
- Direct source links with notes that distinguish numerical support from 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: research standards, sources,disclaimer, and evidence guides.