The reason for a hangover is dehydration.
If you drank a glass of water between drinks, it is likely you will not get a hangover.
However, if you do...
Within an hour or so, you will feel right as rain.
Do not take anything with acetaminophen, unless you want to die of liver failure. It produces a toxin that acts as a pain killer, but if your liver is already taxed from too much alcohol, there is a likelihood it could become overwhelmed and shut down.