Etoposide is soluble in DMSO up to 50mM concentration. I Prepared the solution accordingly and stored in -20 C a year back, now when I checked my stocks I found the solution was clear and a pellet at the bottom of vials. I tapped the vial but it's not solubilizing, what can be done to solubilize etoposide in the same vial.
I have just started working with etoposide but I have noticed it is very sensitive to temperature; at RT the solubility is much better in a 10% DMSO/PBS solution than when the solution is on ice. However, I would be concerned that your etoposide may no longer be active. The white precipitate is a sign of loss of stability (http://link.springer.com/article/10.1007/BF00685638). I store mine in 100% DMSO at -20 then dilute as needed for injections, since Sigma has the stability of etoposide in aqueous solutions at only a few hours/days.
dear michelle,
thank you very much for the link. Its very helpful, now i know that the stocks in which i can see the precipitate might not work. I will check the toxicity of it again and compare with fresh stock. But I am surprised that its stability in -20 C has compromised.
thanks again.
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