Pills & capsules. Assortment of pill and capsule drugs. Some of the capsules have been opened, spilling their white powdery contents. The pink capsule (at upper right) is Praxilene, used to treat and improve mental function in vascular diseases. Oral medication is digested and absorbed by the intestine the same way as food. The rate of action of the drug will depend on the body's ability to absorb the drug. Drugs are chemical substances that alter the function of one or more organs or change the process of a disease. Drugs act by stimulating or blocking chemical reactions, in many cases by mimicking a naturally occurring chemical in the body.