1: Pharmacology Overview

Four Basic Pharmacology Terms

• Drug: Any chemical that can affect living processes.
  • All chemicals can be considered drugs, since, when exposure is sufficiently high, all chemicals will have some effect on life.
• Pharmacology: The study of drugs and their interactions with living systems.
  • It encompasses the study of the physical and chemical properties of drugs as well as their biochemical and physiologic effects.
• Clinical pharmacology: The study of drugs in humans.
  • It includes the study of drugs in patients as well as in healthy volunteers.
• Therapeutics: Also known as pharmacotherapeutics, the use of drugs to diagnose, prevent, or treat disease or to prevent pregnancy.
  • The therapeutic objective of drug therapy is to provide maximum benefit with minimal harm

Properties of an Ideal Drug

• Effectiveness
  • The most important property a drug can have.
  • An effective drug is one that elicits the responses for which it is given.
• Safety
  • A safe drug is one that cannot produce harmful effects—even if administered in very high doses and for a very long time.
  • A drug is both a remedy and a poison.
• Selectivity
  • Selective drug: One that elicits only the response for which it is given.
  • There is no such thing as a wholly selective drug because all drugs cause side effects.
• Reversible Action
  • It is important that effects be reversible.
  • We want drug actions to subside within an appropriate time.
• Predictability
  • To maximize the chances of eliciting desired responses, we must tailor therapy to the individual.
• Ease of Administration
  • An ideal drug should be simple to administer: The route should be convenient, and the number of doses per day should be low.
  • It can enhance patient adherence and it can decrease risk.
• Freedom From Drug Interactions
  • When a patient is taking two or more drugs, those drugs can interact. These interactions may either augment or reduce drug responses.
  • An ideal drug would not interact with other agents.
• Low Cost
  • Drugs should be affordable.
• Chemical Stability
  • Some drugs lose effectiveness during storage.
  • An ideal drug would retain its activity indefinitely.
• Possession of a Simple Generic Name
  • An ideal drug should have a generic name that is easy to recall and pronounce.

No drug is ideal.

Factors that Determine the Intensity of Drug Responses

Administration

• The drug dosage, route, and timing of administration are important determinants of drug responses.
• Accordingly, the prescriber will consider these variables with care. Unfortunately, drugs are not always taken or administered as prescribed.
• The result may be toxicity if the dosage is too high or treatment failure if the dosage is too low.
• Poor adherence — when patients do not take medicine as prescribed.
  • Patients should be given complete instructions about their medication and how to take it.

Pharmacokinetics

• Pharmacokinetic processes determine how much of an administered dose gets to its sites of action.
• Four major processes of pharmacokinetics
  • Drug absorption
  • Drug distribution
  • Drug metabolism
  • Drug excretion

Pharmacodynamics

• Pharmacodynamics can be thought of as the impact of drugs on the body.
• In most cases, the initial step leading to a response is the binding of a drug to its receptor. This drug-receptor interaction is followed by a sequence of events that ultimately results in a response.
• Placebo effects also help determine the responses that a drug elicits