Resources & Guides

Dive deep into pharmacokinetic principles, from basic half-life concepts to complex compartmental models, and understand how individual factors affect drug concentrations.

The definitive guide to retatrutide (reta) pharmacokinetics: approximately 6 days half-life from the Phase 1b trial (Lancet 2022), about 97% gone after 5 half-lives (30 days, by half-life arithmetic), and about 4 weeks to steady state per dose level (estimated from the half-life). Includes half-life comparison to tirzepatide and semaglutide, dosing implications, and FAQ.

How GLP3Planner's calculators model drug levels: a one-compartment model with first-order absorption and elimination (the Bateman function), plotted as milligrams in the body. Each parameter is listed with its source, the assumptions are marked, and the page explains the concentration estimate in the hourly table. Also covers the reconstitution math and the standard titration ladders.

A twice-weekly retatrutide split takes the same total weekly dose and divides it into two injections about 3 to 4 days apart. The 6-day half-life is what makes that spacing logical. Here is the pharmacokinetic reasoning, the practical mechanics, and the honest evidence picture.

Split dosing semaglutide twice weekly takes the same total weekly dose and divides it into two injections about 3 to 4 days apart. Every semaglutide injection is FDA-approved for once-weekly dosing only, so this is off-label. Here is the pharmacokinetic reasoning, the pen-mechanics problem, and the evidence gap.

Everything you need to know about semaglutide (Ozempic/Wegovy): GLP-1 mechanism, FDA-approved dosing protocols, half-life pharmacokinetics, side effects, and our free calculator to track your journey.