The food which we take interferes with the absorption of many drugs. So the effective amount of drug that enters the blood from the stomach and reach the site of action is altered. Depending on the mode of actions the doctors prescribe them "to be taken after or before meals."
Most of the drugs are known to irritate the stomach or increase acid secretion in the stomach leading to discomfort or pain in the stomach, chest burning and occasionally nausea and vomiting. To decrease these side effects some drugs are taken post meals.
Most of the drugs are advised to be taken along with warm plain water. This is to avoid any possible reaction between the active compounds in the drugs and milk, or curd or tea.
Some drugs does not cause any side effects while taking in an empty stomach and may need to be fuly absorbed by the blood stream. In such cases drug is advised to be taken before food.
Excerpted from an article in The Hindu
