Is it though? I mean. Presumably – she’s just taken a drink. Couldn’t she just spit it out? Couldn’t he give her something to help her puke it up? I mean. It’s clear it’s a pretty fast acting poison – but she probably hasn’t even swallowed yet at the point it’s too late.
Granted, it would be hard for Claudius to do anything at this point without making a scene. It is not a surprise to realize that Claudius cares more about protecting himself and/or making a scene than saving his wife’s life – but it does feel important to recognize that that is probably the choice he’s making.