If the need to differentiate between drunk and tipsy arises, use the quote "I'm a bit patchy" to signify tipsiness and just "I'm patchy" to signify drunkenness.
There is also such thing as patchiness, acting as either a noun that signifies the alcohol one has at hand or the overall patchy state of several people.
Random scene kid: WTF!! ROFL HxC SCENE!
European kid: Fag.
Guy: Have you brought the patchiness?
Girl: Hell yes, now let's get patchy!