Glucagon

Glucagon is secreted by pancreatic alpha cells when glucose falls, binding the Gs-coupled glucagon receptor on hepatocytes to raise cAMP, activate glycogen phosphorylase and suppress glycogen synthase. The result is rapid glycogenolysis and, more slowly, increased gluconeogenesis and hepatic fatty-acid oxidation. Those metabolic effects - increased energy expenditure and hepatic fat mobilisation - are exactly what the glucagon arm of retatrutide, survodutide, mazdutide and pemvidutide is exploiting. As a rescue drug its limitation is that it requires hepatic glycogen: it fails in starvation, prolonged fasting, alcoholic hypoglycaemia or adrenal insufficiency. Dasiglucagon is a stabilised analogue that can be supplied ready-to-use rather than requiring reconstitution.

Targets: Glucagon receptor

• · 1 mg for adults and children over 25 kg; 0.5 mg for children under 25 kg. Roll the person on their side - vomiting on waking is very common. Emergency services still need calling.
• · Baqsimi 3 mg is a dry powder that does not need to be inhaled - it absorbs passively, so it works even in an unconscious person.
• · Used to relax gastrointestinal smooth muscle for endoscopy and radiology, and in beta-blocker overdose.

Work out your exact syringe units →

• very commonNausea and vomiting— Very common on waking - aspiration risk if the person is left on their back.
• commonRebound hyperglycaemia— Expected and generally acceptable in a rescue context.
• commonHeadache
• commonNasal irritation and watery eyes— Specific to the intranasal powder.
• rareHypertensive crisis in phaeochromocytoma— Glucagon triggers catecholamine release from the tumour.

• Phaeochromocytoma - risk of catecholamine surge and hypertensive crisis.
• Insulinoma - can provoke rebound hypoglycaemia.
• Glucagonoma.
• Depleted hepatic glycogen (starvation, prolonged fasting, alcohol-related hypoglycaemia, adrenal insufficiency) - glucagon will not work and glucose must be given instead.

• conflictinsulin-analogues — Directly opposing hormones - glucagon exists as the antidote to insulin overdose.
• redundantretatrutide — Retatrutide already contains glucagon receptor agonism as a therapeutic arm.

• · Blood glucose after administration.
• · Level of consciousness and airway.
• · Follow-up carbohydrate once the person can swallow safely.

FDA- and EMA-approved in multiple presentations; prescription-only.

• Baqsimi, Gvoke and Zegalogue US prescribing information (label)
• ADA Standards of Care - severe hypoglycaemia management (guideline)

Glucagon is the counter-regulatory half of the pancreatic glucose system and understanding it properly explains a lot about the dual and triple agonists in this class. The glucagon receptor is a Gs-coupled class B GPCR concentrated in hepatocytes. Activation raises cAMP, activates PKA, and PKA does three things in the liver: it phosphorylates and activates glycogen phosphorylase to break down glycogen, it inhibits glycogen synthase, and it drives gluconeogenic gene expression. The result is a rapid rise in hepatic glucose output - glucose starts climbing within ten to fifteen minutes. The critical clinical limitation follows directly from the mechanism: glucagon rescue works by mobilising hepatic glycogen, so it does not work in someone whose glycogen is depleted. In prolonged starvation, in advanced liver disease, and above all in alcohol-related hypoglycaemia, glucagon may do nothing at all, and that is the situation where people most often reach for it. Intravenous dextrose is the answer there. The same PKA cascade in adipose tissue activates hormone-sensitive lipase, and in the heart it produces positive inotropic and chronotropic effects independent of beta-adrenergic receptors - which is why glucagon is used as an antidote in beta-blocker overdose, and also why every glucagon-containing dual and triple agonist raises resting heart rate. Glucagon also relaxes gastrointestinal smooth muscle, which is why radiologists and endoscopists use it. The modern ready-to-use presentations exist because the old reconstitution kits were failed by caregivers under stress with alarming frequency.

The classic failure is expecting glucagon to work when there is no glycogen to mobilise. Alcohol-related hypoglycaemia is the textbook case: alcohol suppresses gluconeogenesis and the person is often glycogen-depleted, so glucagon does very little and the delay while waiting for it can be dangerous. The second failure is device-related - traditional two-part reconstitution kits are frequently used incorrectly by frightened caregivers, which is exactly why ready-to-use autoinjectors and the nasal powder were developed and why they have their own registration trials showing faster and more reliable administration. The third is not anticipating rebound: glucagon buys 60-90 minutes, and if the cause was long-acting insulin or a sulfonylurea, the hypoglycaemia comes back.

• Glucagon receptor (GCGR), class B1 GPCR — High-affinity endogenous ligand

  Hepatic glycogenolysis and gluconeogenesis raising blood glucose within 10-15 minutes; adipose lipolysis; positive inotropic and chronotropic cardiac effects independent of beta-adrenergic receptors; relaxation of gastrointestinal smooth muscle.

• GLP-1 receptor (GLP1R) — Weak cross-reactivity at supraphysiological concentrations

  Minor and generally not clinically relevant at rescue doses, but it is the structural reason glucagon-based scaffolds can be engineered into GLP-1/glucagon dual agonists in the first place.

Glucose begins rising within 10-15 minutes of subcutaneous or intramuscular injection and within about 15 minutes of the nasal powder. Peak effect at roughly 30 minutes. Duration of the glucose-raising effect is 60-90 minutes, which is the window in which carbohydrate must be eaten.

Glucagon is not a stackable compound - it is emergency therapy and a procedural tool. The relevant interaction knowledge is the reverse direction: anyone using insulin, a sulfonylurea, or a high-dose incretin alongside insulin should have a glucagon rescue product in the house and someone else who knows how to use it, because the person who needs it will not be able to administer it themselves. Beta-blockers blunt the adrenergic warning symptoms of hypoglycaemia, which makes rescue more likely to be needed and later. Note also that a glucagon receptor agonist is the active arm of retatrutide, survodutide, mazdutide, pemvidutide, efinopegdutide and cotadutide - understanding glucagon physiology is what lets you predict their heart-rate and fasting-glucose effects.

Against the glucagon arms of retatrutide, survodutide, mazdutide and pemvidutide: same receptor, entirely different exposure. Rescue glucagon is a single large pulse cleared in minutes; the dual and triple agonists produce weeks of continuous low-level agonism, which is why they raise energy expenditure and heart rate rather than blood glucose. Against dextrose for hypoglycaemia rescue: dextrose is more reliable because it does not depend on hepatic glycogen, but it requires intravenous access. Against the ready-to-use presentations versus the old kits: the newer devices exist because the old ones failed in practice, and that is a genuine improvement rather than a marketing one.

$150–$400/month. Per rescue device rather than per month - glucagon is not a chronic therapy. US retail for a ready-to-use autoinjector or nasal device sits in this range without coverage. Market observation, not verified pricing.

• ?No individual glucagon label was fetched and verified in this session, so bioavailability, volume of distribution and protein binding are left null rather than quoted from memory.
• ?The sequence given is the standard native human glucagon sequence and was not verified against a primary source in this session.
• ?Pharmacokinetics differ substantially between the reconstituted, ready-to-use subcutaneous and nasal presentations, and those differences are not characterised here.
• ?Cost figures are market observations, not verified pricing.

• Glucagon for injection and ready-to-use glucagon presentations - US prescribing information Multiple manufacturers, DailyMed

  Further reading. The individual glucagon presentations (reconstituted kits, ready-to-use subcutaneous autoinjectors and the nasal powder) each have their own label with their own pharmacokinetic section; no single label was fetched and verified in this session, so the pharmacokinetic entries above are left largely null.