Text taken from e-mail to Mike Maul by Teddy Lancaster
The calcium in PNW is readily dissolved in water and therefore is in an 
ionized form while in the intestine, unlike a solid form of calcium, 
requiring the gastric secretions to aid in absorption.  In the ionized 
form, electrolytes travel down the concentration gradient through the ion 
channels in the intestinal tract. The ion moves from the high 
concentration in the gut to a lower concentration in the plasma of the 
capillaries around the intestinal tract.
The dosage for PNW is 3 oz for each hour of exercise, and will provide 
the glucose/carbohydrate blend to optimize absorption of the electrolytes 
and water as well as providing a source of energy that is absorbed by the 
blood over time (preventing the glucose spikes).  This is a guideline and 
must be adjusted for your horse and the conditions.  We see maximum 
levels in the blood in 45-60' following ingestion, therefore, when 
determining dosage, repeat your metabolic checks at that time if possible 
to see if there has been a change in hydration (there should be if water 
is provided at time of ingestion).  If you are offering water from a 
bucket, it is best to mix up the PNW into the water, as this will 
optimize absorption.  Otherwise, administer immediately following a 
drink, for best results.