Open the menu, select the item and use it.
Humor me, why has it not occurred to you to try this? Why was a bug report the immediate conclusion?
Viewing post in [Bug] Cannot fill vials in the lab
Because up until now, whenever an item was required, I could just walk up to it, press the interact key and the item menu would automatically come up. I didn't even know there was a designated item menu until just now, I just thought that was how it worked.
Given that the interact key was the only one that was introduced on screen when the disembodied penis attacked. In any case, sorry for the false alarm.