Pharmacotherapy Health Article

Definition

Pharmacotherapy is the use of medicine in the treatment of diseases, conditions, and symptoms.

History of pharmacotherapy

Pharmacotherapy is not a contemporary science. The use of drugs to treat illness is a practice that has been accepted for thousands of years. A famous example is Hippocrates, who is generally credited with revolutionizing medicine in ancient Greece by using beneficial drugs to heal illness. Traditionally, plants have been the source of medicinal drugs, but modern day medicine in the United States mostly utilizes synthesized or purified bioactive compounds, rather than an entire sample of plant matter. The advantage to this method of pharmacotherapy is that the dose of medicine rendered is standardized and pure, rather than an unknown drug dosage administered in addition to a wide variety of other chemicals present in the plant. Modern pharmacotherapy is the most common course of treatment for illness in the United States.

Pharmacokinetics and pharmacodynamics

Pharmacokinetics is the study of the concentration of a drug and its metabolites in the body over time. A drug that remains in the body for a longer time period will require lower subsequent doses to maintain a specific concentration. How quickly a drug clears from the body is a function of its absorption, bioavailability, distribution, metabolism, and excretion properties.

The absorption of a drug is the rate at which it leaves its site of administration. The bioavailability of a drug describes the extent to which it is available at the site of action in a bioactive metabolic form. A drug absorbed from the stomach and intestine passes through the liver before reaching the systemic circulation. If the liver biotransforms the drug extensively into an inactive form, its availability in bioactive form would be greatly reduced before it reaches its site of action. This is known as the first pass effect. Sometimes the liver biotransforms an inactive drug into an active form.

Which parts of the body drugs distribute to affects the length of time the drugs remain in the body. Fat-soluble drugs may deposit in fat reservoirs and remain in the body longer than drugs that are not fat-soluble. Drugs are metabolized within cells, often into inactive forms. The rate at which a drug is excreted from the body also affects its pharmacokinetics. Pharmacokinetic information about a drug allows the determination of an optimal dosage regimen and form of administration that will produce a specified drug concentration in the body for a desired period of time.

While pharmacokinetics is the study of drug concentration versus time, pharmacodynamics is the study of drug effect versus concentration, or what effect a drug has on the body. Pharmacodynamics measures a quantifiable drug-induced change in a biochemical or physiological parameter. Pharmacodynamics is the study of the mechanism of action of a drug. Medicinal drugs have targets to reach at the site of action. These targets are usually a specific type of drug receptor. Drug and drug receptor interactions can be measured. Complex pharmacodynamic equations combine with measurable pharmacokinetic values to determine the overall effect of a drug on the body over time.