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