Stated plainly: dulaglutide · 2–8 °C.
This is a procedural question rather than a theoretical one, and I would like the procedure rather than the theory.
What I have done so far is read the label documentation where it exists and the two pharmacopoeial monographs that are publicly available, which cover the licensed presentation and say nothing about a research one.
What is the correct sequence, and where is the step that people usually skip?
Whatever the refrigerated figure is, divide it by about 1. 2–8 °C is the condition the rule of thumb is anchored to, so it is the baseline rather than a multiplier: everything else in this thread is quoted relative to it. So a preparation with a twenty-eight day refrigerated figure has roughly 28 days at 2–8 °C on the same assumption — an order-of-magnitude answer, not a shelf life, and it says nothing about sterility, which has its own clock. "Within specification" also needs a specification: purity, content, or both, and at what limit. Without that the question has no numerical answer at all.
Aggregation is a physical process and is the one most often caused by handling rather than by time.
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.
A mass spectrum resolves most of this: minus eighteen is dehydration or succinimide, plus one is deamidation, plus sixteen is oxidation, and an unchanged mass with a shifted retention time is an isomer.
Metal-catalysed oxidation of methionine is documented across peptide and protein formulations and is why chelators appear in some formulations.
Sequence decides which pathways are even available. Check the residues.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemAnswering this needs the physical state, since a dry powder is protected from most of these and a solution is protected from none.
Aggregation is physical: peptides unfold at air-liquid interfaces and associate. Shaking maximises that interface, which is why swirling and shaking produce visibly different outcomes on the same vial.
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.
Aggregation at air-liquid interfaces is established from surface-tension and particle-count studies and is the basis for anti-agitation handling guidance.
Nothing here is medical advice, and research-use compounds are not approved for human use.
A mass spectrum names the pathway. Plus one, plus sixteen, minus eighteen.
The short version: water enables most of it, oxygen enables oxidation, surfaces enable adsorption, and agitation enables aggregation.
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.
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.
The caveat is that none of these pathways can be seen by looking at a vial, and a clear solution can be substantially degraded.
Swirl, never shake. Aggregation is a handling problem more than a time problem.
edited 15 Jul 2024 by deamidation_watch — clarified the distinction between purity and content
This is answerable from the chemistry rather than from anecdote, which is unusual and welcome.
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.
Adsorption losses at low concentrations are quantified in formulation studies and are the reason carrier proteins are used in dilute preparations.
Apparent loss in a dilute preparation is usually adsorption rather than degradation and is worth ruling out first.
Cold, dry, dark, still. Those four words cover most of the mitigation.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.