When a drug is given upon an empty stomach, it is usually absorbed much more rapidly. Thus the same quantity of alcohol which would have no effect on a man if taken during or after dinner, might intoxicate him if taken on an empty stomach, and especially if he were thirsty, so that absorption occurred rapidly. Curare, although it is usually inert when placed in the stomach, is sometimes absorbed so rapidly from an empty stomach as to produce a certain amount of paralysis.

Besides the alterations in absorption we have to consider also the local action on the stomach itself, and the reflex effects which may be produced through the gastric nerves on other organs. Thus where we give a drug for its local action on the stomach itself, it is administered with the greatest effect during fasting, as it will come in contact with all parts of the gastric mucous membrane. An example of this is the use of a small dose of arsenic for gastric neuralgia or lientery.

But when we wish to prevent local action on the stomach - as, for example, when we give arsenic for its general effect on the system, in cases of skin-disease - we administer it after meals, so that it may be diluted by the food, and not irritate the stomach too much.