Sealed, lyophilized vials

  • Long term: −20 °C, in the original sealed vial, protected from light. Most peptides are stable for years under these conditions.
  • Short term: 2–8 °C is adequate for several weeks; room temperature is fine for the days a shipment is in transit.
  • Moisture: lyophilized peptides are hygroscopic. Always let a vial warm to room temperature before removing the cap or piercing the stopper, so water vapour does not condense on the cold powder.
  • Light: residues such as tryptophan, tyrosine and methionine are light- and oxygen-sensitive. Keep vials in their box.

Reconstituted vials

  • Store at 2–8 °C. With bacteriostatic water (0.9% benzyl alcohol) as the diluent, 28 days is the usual limit for a vial that is punctured repeatedly.
  • Sterile water without preservative supports microbial growth; solutions made with it should be used promptly or divided into single-use aliquots and frozen.
  • Avoid freeze–thaw cycles. If a solution must be frozen, aliquot it first and thaw each aliquot once.
  • Do not shake. Agitation causes foaming and can promote aggregation; swirl or roll the vial gently.

Sequence-specific notes

Peptides containing cysteine (AOD-9604), methionine (Semax, MOTS-c) or tryptophan (MOTS-c, PT-141) oxidise more readily and benefit most from cold, dark storage and prompt use after reconstitution. Peptides with aspartate–glycine or asparagine–glycine motifs can undergo isomerisation or deamidation in solution over weeks. Hydrophobic, acylated peptides such as semaglutide and tirzepatide can adsorb to plastic; glass vials and minimal transfer steps help.

Signs a vial should be discarded

Cloudiness, visible particles, discolouration or a cake that has collapsed into a sticky film before reconstitution all indicate the material is out of specification.