Is liraglutide at 4 mg/mL stable enough for twelve weeks of multi-withdrawal use?

The particulars: liraglutide · 4 mg/mL · twelve weeks.

I would like to know whether this claim survives contact with evidence.

If the answer is "nobody has tested that", I would like that stated so I can stop looking.

What would count as evidence here, and does it exist?

twelve weeks is 84 days and, on a weekly schedule, 12 stopper punctures out of one vial at 4 mg/mL. Set the chemical question aside for a moment, because the puncture count is the one with a convention attached: 84 days is 3 times the twenty-eight days conventionally allowed for a preserved multi-dose preparation once it has been entered. Chemically, 4 mg/mL is high enough that adsorption to the glass is a rounding error and low enough that it is not protecting you from anything. What 12 withdrawals do add is 12 opportunities to introduce air, 12 coring events on the same stopper, and a headspace that grows with every draw — none of which show up on a certificate and all of which are avoided by splitting into aliquots at reconstitution.

Answer first: the degradation pathways worth knowing are hydrolysis, deamidation, oxidation, aggregation and adsorption, and each has a different trigger and a different mitigation.

Deamidation converts asparagine or glutamine to the corresponding acid via a succinimide intermediate, adding one dalton. It is base-catalysed, accelerates above neutral pH and is the dominant aqueous pathway for many peptides.

Hydrolysis cleaves the backbone, most readily at aspartate-proline and aspartate-glycine sequences, and is acid-catalysed. In a dry solid it barely proceeds at all.

Cold, dry, dark, still. Those four words cover most of the mitigation.

The short version: water enables most of it, oxygen enables oxidation, surfaces enable adsorption, and agitation enables aggregation.

Oxidation targets methionine, cysteine and tryptophan, adding sixteen daltons per oxygen. It is catalysed by trace metals and promoted by dissolved oxygen and by light.

Mechanically, light exposure matters for tryptophan-containing sequences and for anything with a chromophore. Amber vials and a closed box are free mitigations.

Sequence decides which pathways are even available. Check the residues.

Asparagine and glutamine are the deamidation risk, and methionine is the oxidation risk.

Adsorption onto glass and plastic is significant at low concentrations — micrograms per millilitre — and negligible at milligrams per millilitre. It is the usual explanation for an apparent loss in a dilute preparation.

Stated carefully, freeze-thaw cycling drives aggregation through concentration at the ice interface and pH shifts as buffer components crystallise out at different rates. Each cycle costs something.

The caveat is that none of these pathways can be seen by looking at a vial, and a clear solution can be substantially degraded.

At dilute concentrations, suspect adsorption before you suspect chemistry.

edited 22 Mar 2026 by tyndall_haze — removed a claim I could not source