Instructor Notes — Chapter 29

Part 5 · intermediate · prerequisites: Chapters 3, 11, 28 Estimated contact time: one 90-minute session, or two 50-minute sessions split at §29.7.

What this chapter is actually doing

Chapter 29 looks like a survey chapter. It is not. It is an argument chapter wearing a survey's clothes, and if you teach it as a list of drugs to memorize you will have taught the wrong thing.

The argument has two moves. The first is easy and satisfying: students discover that a category they thought was small and speculative is large and mature. The second is harder and is the whole point: having built the inventory, students look at what is in it and notice what is not — that no approved peptide drug exists to broadly support, optimize, or enhance a healthy system.

The chapter is quietly persuasive rather than loudly persuasive, and that is deliberate. It makes no accusation. It contains no scandal. It never says a gray-market compound does not work. It simply lays out the approved pharmacopeia and lets the shape of it do the arguing. Students who have been mildly resistant to earlier chapters often come around here, precisely because nothing is being sold to them.

Protect that. The temptation in the classroom is to make the point louder than the text does. Don't. The text's restraint is the mechanism.

Open with the recall test — do not skip it

Begin the session by asking students, cold, to name three peptide drugs. Write the answers on the board. Do this before any framing.

You will get insulin and semaglutide, and then silence, and then possibly oxytocin from someone who remembers Chapter 21. Write down how many distinct molecules the whole room produced. Leave it on the board for the entire session and return to it at the end.

This takes four minutes and it does more work than any lecture opening you could write. The gap between the board at minute four and the board at minute eighty-five is the chapter.

Section-by-section teaching notes

§29.1 — the inventory. The hospital-pharmacy paragraph is the one to read aloud. Then push the "note on the count" harder than the text does: ask students to propose an inclusion rule, then ask what their rule does to the total. This is the chapter's first small lesson in the difference between a number and a claim.

§29.2 — teriparatide. Budget the most time here. This is the best story in the chapter and it is the one students remember six months later.

The teaching sequence that works: establish that PTH destroys bone (uncontroversial, well documented, classic hyperparathyroidism), let that sit, then announce that PTH is an approved osteoporosis drug and let the room object. Take the objections seriously — they are correct objections. Only then introduce the temporal variable.

The payoff line is that the only variable that changed is the shape of the exposure over time. If students leave with one sentence from this chapter, that is a good candidate.

Handle the osteosarcoma labeling history carefully. The failure mode is students concluding that animal safety findings are overblown. The text explicitly forecloses that reading and you should too. The correct lesson is narrow: the specific question got answered by evidence and the label followed the evidence, in both directions.

§29.3 — desmopressin. This section teaches receptor subtype selectivity better than an abstract treatment would. The diagram earns its space; put it up.

The rule-6 demonstration here is worth pausing on. Two ratings, same molecule, same receptor, same mechanism — and one of them is a permanent physiological correction while the other is a symptomatic treatment that frequently stops working when stopped. Ask the class what a single molecule-level rating would have hidden.

§29.4 — calcitonin. The pedagogically richest section, and the one most likely to generate real discussion. See the discussion guide below.

The transferable skill here is the dose-response reading. Most students have never been taught to read a multi-arm trial for whether the arms line up rather than for which arm carries the p-value. Teach it explicitly; it generalizes to everything.

§29.5 — critical care. Light touch. The 💊 In the Clinic callout is the deliverable: clinicians organize by function and therefore cannot see the category. Read it, make the point, move on.

§29.6 — glucagon. The delivery-problem contrast is the teaching asset. Every delivery problem in Chapter 4 is molecule-versus-body. This one is product-versus-user, and no technique from Chapter 4 touches it.

Ask the class: who is holding this device? The answer — a frightened bystander at 2 a.m. — reframes the whole engineering problem in one sentence. Students in health professions often find this section the most immediately useful in the chapter.

§29.7 — diagnostics. Short and pleasant. The secretin callback to Chapter 3 is a nice moment; flag it. The transferable idea is that diagnostic peptides get retired by better measurement, not by being disproven — a third mode of obsolescence alongside §29.4's.

§29.8 — the surprise. Deliver cyclosporine as a reveal. "It is a cyclic undecapeptide" gets a mild reaction; "and it is taken orally" gets the real one, because by Chapter 29 students know exactly why that should be impossible.

Then be strict about what the exception licenses. It proves oral peptide bioavailability is an engineering problem rather than a physical impossibility. It does not license believing any given oral peptide product. The burden stays with the seller (Ch 1 §1.6).

§29.9 — modern approvals. Linaclotide is the conceptual inversion: bioavailability as the enemy. The generalizable line — a peptide's confinement to a compartment is a limitation only relative to a target outside that compartment — is worth writing on the board.

§29.10 — the payoff. Do not rush this and do not soften the objection. The regulatory-artifact objection is genuinely good, the text concedes that it is partly right, and the concession is what makes the three responses credible. A class that has been handed the objection at full strength and then talked through the responses will hold the conclusion much more firmly than a class that was told the conclusion.

End by returning to the board from minute four.

Common student difficulties

"So you're saying these gray-market peptides don't work." No. The chapter is careful about this and you must be too. The prior says a claim of that type has never obtained approval. It does not say any particular claim is false. Students who overshoot here have learned a slogan, not a method.

Confusing "not approved for X" with "shown not to work for X." Recurs throughout. Worth a direct five-minute treatment.

Treating the empty box six as self-evidently damning. The objection exists, it is partly right, and a student who cannot state it in its strongest form does not understand the argument.

Assuming teriparatide means "pulsatile dosing is better." It means temporal pattern is a design parameter with a determinable answer. Sometimes the answer is intermittent. Sometimes it is not.

Reading the calcitonin story as a scandal. Some students cannot accept a story with no villain. That resistance is itself worth discussing.

Assessment notes

• exercises.md ships without answers; marking guidance is in _scratch/answers/ch29.md, including explicit instructions to penalize (a) confident extrapolation of the teriparatide rating to unstudied populations, (b) drift into management protocols on the desmopressin item, and (c) any answer concluding a compound "does not work" from the box-six prior.
• The † items are the ones to grade for reasoning rather than recall. AJ (steelman the objection) and AK (apply the prior with discipline) are the two best single indicators of whether a student has the chapter.
• Quiz items 3, 12, 21, and 22 are the short-answer items that separate students; the multiple-choice items are recall checks.
• Case Study 1 pairs naturally with a Chapter 3 review; Case Study 2 pairs with Chapter 5's rating rules and works well as a standalone seminar reading for students who have not read the chapter.