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Tirzepatide

Metabolic

Also known as Mounjaro, Zepbound, LY3298176

GIP and GLP-1 receptor dual agonist. FDA approved.

How it works

A GIP-based peptide that activates both the GIP and GLP-1 receptors. Slows gastric emptying, increases insulin secretion in response to glucose, and reduces appetite. Bound to albumin via a C20 diacid, which is what gives it a weekly half-life.

Subcutaneous

In the body

Half-life
5 days
Time to peak
24 h
90% gone after
16.6 d
Builds up to
1.61×
Steady state after about 25.3 d at once weekly.
Aug 3Aug 6Aug 9Aug 12Aug 15Aug 18Aug 2112:09 PM

Shape of a single dose, modelled as one compartment with first-order absorption. The peak is normalised to 100% because bioavailability and volume of distribution are not published for most of these compounds.

About 5 days per the label; population PK gives 5.4 days.

What happens, and when

  1. 0 min, 8 hAbsorbing. Gastric emptying starts to slow.
  2. 8 h, 2 dPeak plasma levels, median at 24 hours. Nausea, if it comes, usually peaks here.
  3. 2 d, 5 dHalf of peak by day 5. Steady appetite suppression.
  4. 5 d, 7 dTrough. About 41% of peak remains at day 7 before the next dose.

Doses

2.5 mg, 15 mgonce weeklyApproved label

2.5 mg is a starting dose only and is not intended for glycaemic control.

Label escalation to 15 mg

Zepbound and Mounjaro prescribing information, section 2 · 32 weeks total

  1. wk 1, 42.5 mgStarting dose.
  2. wk 5, 85 mg4 weeks
  3. wk 9, 127.5 mg4 weeks
  4. wk 13, 1610 mg4 weeks
  5. wk 17, 2012.5 mg4 weeks
  6. wk 21, 3215 mg12 weeks

Each step is held at least 4 weeks. Maintenance doses for weight management are 5, 10 or 15 mg.

Vial sizes

2.5 mg5 mg7.5 mg10 mg12.5 mg15 mg

Commonly treated as good for 30 days refrigerated once reconstituted.

Side effects

  • Nausea, diarrhoea, vomiting, constipation, the dose-limiting effects
  • Injection site reactions
  • Delayed gastric emptying, strongest after the first 5 mg dose and diminishing thereafter
  • Gallbladder disease and pancreatitis, uncommon

Cautions

  • Boxed warning: thyroid C-cell tumours in rats. Contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
  • Known hypersensitivity to tirzepatide.
  • Caution with insulin or sulfonylureas, risk of hypoglycaemia.

Status

FDA approved as Mounjaro (type 2 diabetes) and Zepbound (weight management, obstructive sleep apnoea).

Sources

Reference information for personal record-keeping. Not medical advice, and not a recommendation to use any of these compounds.