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Daily Challenge
5 questions · time bonus

Plasma concentration simulator

Adjust half-life and dose interval to see single-dose and repeated-dose curves. Steady state is reached at roughly 5 half-lives. The model is a simple one-compartment first-order absorption / elimination textbook approximation.
Single dose Repeated dosing Steady-state line

Receptor lab — agonists, antagonists, and friends

Imagine a receptor with some baseline activity. Different ligands change it in different ways. Click any ligand to see what happens.
Baseline activity
Activity: 50%
Click a ligand to see how it changes receptor activity.

Educational interaction checker

Pick at least two items below. This is a curated teaching dataset — not a clinical tool. Real interactions depend on dose, timing, kidney/liver function, genetics, and other meds.
⚠ This is not exhaustive. Tell your pharmacist about every medication, supplement, and herbal product you take — including OTC pain relievers, antacids, and grapefruit juice.

1. How pills are identified — the 4 axes

Every US prescription tablet/capsule has an FDA-registered identity built from four visible features. Pharmacists and the FDA's Pillbox database use the same axes.

① Imprint

Letters, numbers, or logos stamped or printed on the pill. Manufacturers register these with the FDA. Always the most specific identifier — look here first.

② Shape

Round, oval, capsule, square, diamond, triangle, pentagon, hexagon, oblong, kidney/bean. Often manufacturer-specific.

③ Color

Primary (and sometimes secondary). Capsules often have two halves of different colors.

④ Scoring

Score lines for breaking the pill. Options: none, single (one line), cross (two lines crossing). Scored pills can usually be split; unscored ones often shouldn't be.

2. Educational gallery — 12 example pills

Pick a pill below to see how its 4 identifying features describe it. These are publicly known generic examples for learning — many distinct pills share the same shape/color/score, so the imprint is critical.

3. Red flags — when NOT to take a pill

Stop and ask a pharmacist if you see:
  • No imprint at all — could be a supplement, an over-the-counter generic, or a counterfeit. US prescription tablets must have an imprint (a few OTC and some homeopathic products are exempt).
  • Worn, smudged, or partial imprints — old or improperly stored pills. Even a partial code can sometimes be matched, but a pharmacist should confirm.
  • Loose pills not in original packaging — you lose the manufacturer, lot number, and expiration date. Never combine pills from different bottles "to save space".
  • Pills that look slightly different from your usual refill — generic manufacturers can change. Confirm with your pharmacist before taking; never assume.
  • Pills bought online from unverified sources — counterfeit fentanyl-laced pills are a documented cause of US overdose deaths. The DEA, FDA, and CDC warn that pills bought outside a licensed US pharmacy may be deadly.

Sources

Based on: FDA Pillbox program (National Library of Medicine educational pages), USP General Chapter <1051> tablet identification framework, DEA imprint code registry, and DailyMed structured product labels. Every prescription pill made or distributed in the United States must have a unique, FDA-registered imprint code — see FDA NDC Directory for manufacturer lookups.

Achievements

Reset progress

Clears scores, achievements, SRS state, and the saved daily result. Cannot be undone.