PK Curve Comparison: Psychiatric Drug Half-Lives

What it shows

This tool draws estimated plasma concentration-over-time curves for psychiatric medications so you can see, side by side, how quickly each drug peaks and how long it lingers. It is useful for teaching and for thinking through dosing intervals, washout and the timing of side effects. Choose a category (antidepressants, antipsychotics, anxiolytics, mood stabilizers, sleep aids, stimulants, non-stimulant ADHD drugs, VMAT2 inhibitors, substance use, or other), then tick up to 8 drugs to overlay. Only drugs with both a Tmax and a half-life on file appear.

How the curves are built

Each curve uses a simplified Bateman equation, a single-compartment oral absorption model. The elimination rate comes from the drug's half-life, and the absorption rate is solved so that the curve peaks exactly at the listed Tmax. A dot on each curve marks one half-life after the peak.

Peak height is not a concentration. It is scaled to the drug's strongest receptor binding affinity (lowest Ki) on file: lower Ki means stronger binding and a taller peak. Heights range from 15% to 100%. Drugs with no receptor Ki data get a neutral height of 50%. The y-axis is therefore a relative scale for comparing shapes, not a measure of plasma level.

Controls

• Time window: Auto (long enough to show about 2.5 half-lives past the latest peak) or fixed windows of 6, 12, 24, 48 or 72 hours, or 1 week.
• Top 5: loads the first five drugs in the selected category, in alphabetical order.
• Zoom: scroll on the graph to zoom the time axis; Reset Zoom restores it.
• Hover: shows each drug's relative level at that time point.
• Legend: lists each drug's Tmax, half-life, primary receptor and any formulation note; click an entry to hide or show its curve.

Limitations

Real pharmacokinetics vary with food, genetics, formulation, drug interactions and individual metabolism. The model ignores active metabolites, multi-compartment distribution, steady state with repeated dosing, and non-oral routes. The curves are a teaching aid and are not for clinical dosing decisions.