Like Barrister said, not much to do but stay hydrated, try to replace those mineral salts that you have lost by sipping something replenishing (coconut water or gatorade or pedialyte) and if anything happens that starts to worry you beyond the 'normal' running from both ends then head to the hospital...fast.
Abnormal includes fainting, severe headache, sharp pains so strong that you are doubled over, chills, a fever above 99°, vomiting strong and uncontrollable to the point of feeling like your guts are coming out etc...you probably know this already.
Things that you can use to help this along would be rice water (cook a pot of rice with double the water and then drink the excess...it is pure starch and thickens output nicely), charcoal tablets or burnt toast (the charcoal absorbs some of the impurities in the guts supposedly)...also I have personally found that Gravol or Dramamine (the motion sickness medication that is OTC) is good to slow things down. I use the children's version that dissolves under the tongue...it slows the gut nicely and helps you to get some sleep.
Feel better
Sharon