Pharmacology is the study of drugs and the way they interact with living systems.  Clinical pharmacology is the study of drugs in humans.

A drug is any chemical that can effect living processes.

Therapeutics: the medical use of drugs.

An ideal drug has several important properties.  Three of these properties are of utmost importance: effectiveness, safety and selectivity.  

Effectiveness: This is the most important quality that a drug can have.  Effectiveness refers to the drug's ability to do what it is supposed to do.

Safety:  Although no drug can be totally safe, proper usage can lessen the risks of adverse         ffects.

Selectivity:  A truly selective drug would have no side effects, and would effect only the body process' for which it is designed and given.  Therefor, there is no such thing as a selective drug.

Other properties of an ideal drug include reversibility, predictability, ease of administration, freedom from drug interactions, low cost, chemical stability and possession of a simple generic name.  No drug is really ideal then, because meeting all of these goals is an impossibility.  

"First do no harm" is a goal that we'll hear over and over again as nursing students, and later as nurses.  It makes sense then that the therapeutic objective of using drugs in the medical setting is to "provide the maximum benefit with minimum harm (5)."

Pharmacokinetics: The way the body deals with a drug.  Pharmacokinetics is concerned with the processes of absorption, distribution, metabolism and excretion.

Pharmacodynamics:  What a drug does to the body.

Pharmacokinetics and pharmacodynamics are two of the processes that determine how a person will respond to a drug.  Other factors include how a drug is administered (dose, route, and timing of administration), interactions with other drugs, and individual physiological variables (weight, age, function of body systems).