Case study

See the curve before you commit.

The math describing how a drug builds up and washes out of the body has been published for decades. It just usually lives in journal papers, not in anything a person can use. This tool puts a pharmacokinetic model behind an interactive chart — change the plan, watch the curve.

Product: Tirzepatide PK Scheduler — a personal project
Scope: PK math engine, comparison UI, dose logging, self-hosted
Stack: React · TypeScript · Recharts · Express
Fine print: Educational tool — not medical advice, not a medical product

The problem: dosing decisions are made blind

Tirzepatide — like many long-half-life drugs — doesn't do anything intuitive between injections. Concentration climbs for a day and a half, decays for days, and stacks dose over dose for weeks before reaching steady state. Questions like "what actually happens if I stretch the interval from 7 days to 10?" have precise, computable answers. Nobody computes them.

So this does: a one-compartment pharmacokinetic model with first-order absorption, with parameters validated against the published literature, running live under a chart. Every dose you add or move recomputes the whole concentration curve by superposition, instantly.

The scheduler comparing two dosing plans: a blue baseline curve and an orange experiment curve on one chart, with key metrics showing the percentage change in peak, trough, and total dose — Baseline in blue, experiment in orange — and every metric shows what the change costs you.

The mobile chart view showing both concentration curves — A phone-first mode for logging doses and checking today's level.

Baseline, experiment, actual

The design centers on comparison. A baseline plan — say, the FDA's standard titration schedule, available as a one-click template — sits next to an experiment: a different dose, a different interval, a skipped week. The chart overlays both curves, and the metrics panel scores the difference — peak, trough, average, peak-to-trough ratio, total milligrams — each with a percentage delta. What-if becomes a number instead of a guess.

A third plan type, actual, holds what really happened: logged doses, weights, injection sites, how the day felt. That turns the tool from a calculator into a record — plan against model, then check the model against life.

Built for personal use, self-hosted, and deliberately labeled: it's an educational tool, not medical advice. The engineering point stands on its own — published math, turned into something a person can hold.

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