Bridge therapy

Bridge therapy is a temporary substitution meant to keep you on treatment when your usual medication is unavailable — a shortage, a stockout at your pharmacy, a coverage lapse between plan years, or a gap while an appeal is pending. The intent is to get you back to the original drug, not to change course permanently.

The reason this concept exists in GLP-1 care is that supply has been genuinely unreliable. FDA maintains a public drug shortage database where the current status of specific presentations can be checked, which is a more reliable starting point than a pharmacy’s verbal report.

Bridging within this class is not a simple swap, because the drugs are not interchangeable milligram for milligram. Moving between semaglutide and tirzepatide, or between a weight-indicated and a diabetes-indicated product of the same molecule, means re-entering a dose ladder rather than matching the number on your old pen. Restarting too high invites the nausea and vomiting that made titration schedules necessary in the first place; restarting too low costs you appetite control.

One bridging route deserves particular care. Compounded versions are sometimes used to cover a gap, and the regulatory footing there depends heavily on whether the pharmacy operates under section 503A or 503B and on whether FDA still lists the drug as in shortage. A compounded product is not an FDA-approved one, and the terms change when a shortage is resolved.

Worth asking your clinician before a gap happens: what the fallback plan is, what dose you would restart at on return, and how long you can safely be off. Our switching guide, dose-equivalence calculator and titration planner map the ladders, and our compounded rankings cover how we assess those suppliers.