# Caffeine pathway

Source: Orca session `omp_ac57d63a_0517_495a_bb5d_94be9f125bc2`, native session `01a155d0-4b5f-7446-a47a-a0082b42b981`, October 19, 2026.

This is the original session write-up, preserved verbatim below. Desktop paths and verification claims refer to that original session, not this import. The full physician-level reference notes are preserved in `../renders/anatomy-caffeine/notes.html` and embedded below the figure in both rendered HTML pages.

Educational material only; not a clinical protocol. The original author explicitly states that the medical notes were written from memory and not checked against sources. Independent clinical review is required before teaching or patient-care use.

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I built the caffeine figure and opened the light version in your browser. It's in `~/Desktop/02_projects/anatomy-caffeine/`. Both themes pass the skill's line check with no floating line ends, and the browser console is clean.

**How to read it.** It's a lab bench where each part stands for one step of the caffeine pathway:
- **Gut column (left):** holds a 200 mg dose (about two cups of coffee) and drains into the blood. About 100% is absorbed, peaking at about 50 min.
- **Plasma column (centre):** blood level in mg/L. Caffeine spreads through total body water (0.6 L/kg). The red tick marks the level where caffeine's binding strength equals the receptor's (15 µM).
- **CYP1A2 block (liver):** its valve sets how fast caffeine is cleared. Three tubes collect what it turns into: paraxanthine 84%, theobromine 12%, theophylline 4%.
- **Receptor board and flywheel (front):** 12 sockets are the brain's adenosine receptors (A1/A2A).
  - Grey pegs are adenosine, the sleep-pressure signal; they press a brake on the flywheel, which stands for wakefulness.
  - Lit pegs are caffeine; they fill sockets but push nothing, so the brake lifts and the wheel spins faster.
  - The teaching point: caffeine doesn't stimulate, it takes the brake off.
- **Timer dial:** hours since the dose.

**Controls.** Hover the figure to move through time; click it to switch patient. There's also a time slider below the card, since hover doesn't work on a phone.

| Patient | Half-life | Dose left at 8 h (2 pm coffee, 10 pm bed) |
|---|---|---|
| Healthy adult | 5 h | 34% |
| Smoker | 3 h | 17% |
| Oral contraceptive | 10 h | 58% |
| Third trimester | 15 h | 70% |
| Fluvoxamine | 30 h | 84% |

**Physician-level notes** sit below the figure:
- ADME numbers (absorption, distribution, metabolism, excretion)
- A table of the four receptor types: signalling, location, and what blocking each one does
- Organ-by-organ effects
- Pearls: hold caffeine 12–24 h before an adenosine or regadenoson stress test; it blunts adenosine for SVT; caffeine citrate dosing for apnoea of prematurity
- What changes the half-life: smoking cessation, OCPs, pregnancy, fluvoxamine, cirrhosis, neonates
- Withdrawal timeline
- Toxicity levels and management: esmolol, benzodiazepines, haemodialysis

**Limits.**
- The figure is a simplified teaching model: 70 kg patient, one fixed afternoon adenosine level, and one combined receptor binding value. Each patient gets a fixed typical half-life.
- The notes' numbers are from memory of the standard literature. I didn't check them against sources in this session, so verify before you teach from them.

Files are in `~/Desktop/02_projects/anatomy-caffeine/`:
- `caffeine.html`
- `caffeine-light.html`
- `preview-dark.png`
- `preview-light.png`
- `build.mjs` (rebuild with `node build.mjs` and `node build.mjs --light`)
- `notes.html`