If you want your medication to kick in as fast as possible, lay down on your right side. It beats standing up, according to a computer model of the human stomach.
From New Atlas:
Led by Prof. Rajat Mittal, a team at Johns Hopkins University set out to see which body position would work best for getting a pill the lowest in the shortest amount of time. In order to do so, they created a computer model of the human stomach, known as StomachSim. That model simulates what takes place inside the stomach as food – or in this case a pill – is digested.
Common sense would seem to dictate that an upright posture would be the best bet. However, due to the asymmetric shape of the stomach, it was found that lying on the right side allowed a pill to dissolve 2.3 times faster than if it were taken while standing upright.
In other words, whereas a pill taken when standing would take 23 minutes to dissolve, it would only take 10 minutes when lying on the right side. Lying on the left side is the worst choice, with the pill taking over 100 minutes to dissolve.