It is a widespread minhag that during the mention of the makkos at the Seder one should either spill out wine or dip a finger into the cup and put it to the side.
I have heard that one should not drink this wine, or even the wine left on the fingers from dripping it on the plate. I'm told that just like the malachim were unable to sing shirah because it's rejoicing at others' downfall, we should not drink from the wine used to represent the Egyptians' downfall and gain benefit from it. Is this accurate, and if so, what is the source (i.e. sefer that discusses this)?
Artscroll's The Answer Is... Haggadah (page 148-149) quotes Rav Yechezkel Abramsky and Rav Eliyashiv as saying that this is why we spill it, and the Alter of Slabodka as saying that we should not be happy about human beings, created b'tzelem Elokim, being killed. It does not say. anything about drinking the wine, however.
Highly related: Is the wine spilled at the Seder "cursed"? This is not a duplicate, as that discusses actually discarding the wine, not refraining from drinking it.