Chapter 3 Pharm

Principles of Pharmacology

Chapter 3

What the body does to the drug

Pharmacokinetics

What the drug does to the body

Pharmacodynamics

Overview

Understanding the use of drugs in the treatment of disease

Pharmacotherapeutics

Drug Names

It is crucial to know the different names of a drug

• Generic name-Most common name
• Trade name; brand name (followed by a ® symbol)-Usually easier to pronounce
• Chemical name-harder to remember, longer names

Types of Drug Actions

Drug attachment & REceptor sites

Antagonist: Drug attaches at drug receptor site, but no chemical drug response is produced and the drug prevents activation of the receptor.

Agonist: Drug attaches at receptor site and activates the receptor; the drug has an action similar to the body's own chemicals. Partial Agonist: Drug attaches at drug receptor site, but only a slight chemical action is produced.

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Absorption

Distribution

Metabolism

Once the drug is absorbed & distributed in the body, it is transformed or altered into active/inactive chemicals

The ways a drug moves by means of circulating body fluids to their sites of action in the body

How a drug enters the body and passes into the circulation

Absorption processes: Solubility—ability of a drug to dissolve Diffusion—high to lower concentration Filtration—a filter prevents passage of certain molecules Osmosis—diffusion through a semipermeable membrane from a less dense solution to a more dense solution The route of administration influences absorption. Enteral Parenteral Percutaneous Intramuscular Percutaneous Sublingual Buccal

Blood system Lymph system Barriers: Blood–brain Placental

Biotransformation-Usually occurs in the liver; enzymes break down the chemicals into useful partsFirst-pass effect-Much of the drug is inactivated on it's first pass through the liver before being distributed to the body Affected by genetic and developmental factors

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Excretion

Basic Drug Processes

Inactive chemicals, by-products, and waste removal

GI tract—passes the fibrous/insoluble waste Kidneys—filters & excretes chemicals that may be made water-soluble Lungs—chemicals may be exhaled Skin—chemicals may be lost through evaporation during sweating

Half-Life

The amount of time it takes the body to remove 50% of a drug from the body.

Helps explain the dose, frequency, and duration for different drugs.

Expected response of the drug

Surprise!

Strange, peculiar, or unpredicted responses;from missing/defective metabolic enzymes, caused by genetic/hormonal

When the drug does what is desired & the Therapeutic goal is reached

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Idiosyncratic reactions

Desired action

Usually mild, but annoying responses to the drug

Anaphylactic reaction

Some common allergies, may be life-threatening; Sulfa, aspirin, penicillin

These are expected effects; usually GI related

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Hypersensitivity or allergy

Side effects

More severe symptoms or problems

Basics of Drug Action

May require hospitalization or be life-threatening

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Adverse reactions

Bioequivalence

1. Brand name versus generic-Patent for 17 years; brand usually more expensive
2. Generic equivalent-Identical with respect to active ingredients
3. Bioequivalent-Chemically the same as the brand name product

Antagonistic effect

Additive effect

Drugs given together because they have an additive effect and work as a team

One drug interfering with the action of another. Flumazenil displaces sedative effects of diazepam.

Drug Interactions

Synergistic effect

Adverse effect

LOREM IPSUM DOLOR SIT

When one drug changes the action of another drug. Usually takes place during metabolism.

One drug making another less effective. Many antibiotics make birth control less effective

Effects of two drugs taken together where the sum is greater than when taken alone

Food, Alcohol, and Drug Interactions

Food interactions

Drugs and laboratory tests

Personal Factors

Alcohol interactions

Because both drugs and alochol are processed in the liver, it can cause potential interactions. Alcohol can affect the availability of the drug.

• Hydration problems
• Low blood pressure
• Shock
• Heart failure
• Reduced blood flow
• Ethnicity/Race
• Body size and lean-to-fat ratio
• Liver problems

Caffeine can affect the action of some drugs. Some may increase effects of anticlotting drugs. Some can't be taken with aged cheese, red wine, or many processed foods. Certain juices can affect absorption.

Many drugs can cause interactions with other drugs, so it is vital for nurses to understand possible interactions.

Drug Cards

Drug cards should include the following info:

1. trade and generic name of the drug
2. the dosage range
3. the desired action
4. expected side effects
5. adverse effects
6. how to give the drug
7. important information that you will need to know before to giving the drug