When to switch, how to taper, what dose to start the new agent. Clinical guidance from our endocrinology reviewer.
About this article
Reasons to switch
- Intolerable side effects on current agent.
- Plateau at maximum dose with no further weight loss.
- Coverage/cost change.
- Indication-specific labeling (e.g., Zepbound OSA).
Sema → Tirz (most common switch)
No washout typically required, but coordinate with prescriber. Start tirz at 2.5 mg for 4 weeks then standard titration — do not skip ahead even if you were on max sema.
Tolerance to GI side effects on sema does not fully transfer to tirz; the second mechanism (GIP) creates new exposures.
Tirz → Sema (less common)
If switching for cost or weight stall on tirz: start sema at 0.25 mg for 4 weeks then standard titration. Weight loss with sema after maximum-dose tirz is usually modest.
Branded → compounded
Same active ingredient (sema → sema, tirz → tirz): typically resume at the dose you were at, with brief observation for tolerance changes from any excipient differences. Confirm with prescriber.
Compounded → branded
Insurance considerations driving the switch. Same active ingredient: resume at corresponding dose. Pen-injector technique may need brief training if coming from vial.