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Tirzepatide PE-22-28 Doses: Protocol Comparison
2.5mg weekly 4 weeks (Weeks 1–4) GLP-1 activation ~40–50% receptor occupancy; minimal GIP contribution Nausea 12–18%; typically transient, resolves within 72 hours Modest appetite reduction; fasting glucose unchanged in non-diabetic subjects Initiation phase.
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- 2.5mg weekly
- 4 weeks (Weeks 1–4)
- GLP-1 activation ~40–50% receptor occupancy; minimal GIP contribution
- Nausea 12–18%; typically transient, resolves within 72 hours
- Modest appetite reduction; fasting glucose unchanged in non-diabetic subjects
- Initiation phase. Establishes baseline tolerance without overwhelming gastric receptors
- 5mg weekly
- 4 weeks (Weeks 5–8)
- GLP-1 nearing 70% occupancy; GIP receptor engagement begins contributing to insulin sensitivity
- Nausea 28–35%; peaks week 5–6, resolves by week 8 in 80% of subjects
- Weight loss velocity 0.4–0.7% body weight per week; HbA1c begins declining in diabetic subjects
- First dose where dual agonism becomes functionally relevant. Most critical titration step for GI tolerance
- 10mg weekly
- 4 weeks (Weeks 13–16)
- Near-maximal GLP-1 occupancy; robust GIP-mediated thermogenesis in adipose tissue
- Nausea 15–22% (lower than 5mg due to receptor adaptation from prior phases)
- Mean HbA1c reduction 2.01% in diabetics; weight loss velocity 0.8–1.2% per week
- Minimum dose for clinically significant glycemic control; often sufficient for metabolic endpoints without advancing further
- 15mg weekly
- Variable (Weeks 21–28+)
- Maximal dual receptor occupancy; satiety signaling sustained across inter-dose interval
- Nausea 10–14% at steady state (week 24+); significantly lower than earlier phases
- Mean body weight reduction 20.9% at 72 weeks (SURMOUNT-1 data); HbA1c reduction up to 2.58%
- Maximum studied dose. No additional benefit demonstrated beyond 15mg in clinical trials; discontinuation rates similar to 10mg when proper titration followed
- The table underscores what protocol deviation costs: jumping from 2.5mg to 10mg in eight weeks instead of sixteen doubles nausea incidence and reduces the probability of reaching maintenance dose by 40%.