ABSTRACT
For a drug to achieve its required effect, a sufficient quantity of drug must be distributed to the site of action and its concentration must be maintained, within certain limits, for the required period of time. Often transport via the bloodstream is required for the drug to reach the site of action, but sometimes it is appropriate to administer the drug locally. Some individuals have difficulty swallowing tablets, some drugs are destroyed by the acidic environment of the stomach, and some drugs might be metabolized by first-pass metabolism, so it can be advantageous to administer the drug in other ways than by mouth.
