Alkalis should be given before food. Iodin and iodids should be given
on an empty stomach, when they rapidly diffuse into the blood. If given
during digestion the acids and starch alter and weaken the digestion.
Acids, as a rule, should be given between the digestive acts, because
the mucous membrane of the stomach is in a favorable condition for
the diffusion of the acids into the blood. Acids may be given before
food when prescribed to check the excessive formation of the acids of
the gastric juice. By giving it before meals you check the osmosis
stomachward of the acid-forming materials. Irritating and dangerous
drugs should be given directly after food, such as the salts of
arsenic, copper, zinc, and iron, except where local conditions require
their administration in small doses before food. Oxid and nitrate
of silver should be given after process of digestion is ended; if
given during food, chemic reactions destroy or impair their special
attributes and defeat the object for which they were prescribed.
Metallic salts, especially corrosive sublimate, also tannin and pure
alcohol, impair the digestive power of the active principle of the
gastric juice, so should appear in the stomach during its period of
inactivity. Malt extracts, cod-liver oil, phosphates, etc., should be
given with or directly after food, so that they may enter the blood
with the products of digestion.