Pharmacology 101

Abdelkader Ashour, Ph.D.

1st & 2nd Lectures

B. Basic concepts in Pharmacology -Drug-Body Interactions

-Drug Receptors

-Drug Receptor Interactions

Overview

A. Introduction -Definitions

-Drug Sources

-Drug Nomenclature

Pharmacology, link to other biomedical principles

Receptor “A specific protein in either the plasma membrane or interior of a target cell with which a chemical messenger/drug combines”

Pharmacology, Definitions

Pharmacology“A branch of medical sciences that study drugs and their action on living organisms”

Why do nurses study pharmacology? A sound knowledge of basic pharmacologic principles is essential if the nurse is to safely administer medications and to monitor patients who receive these medications

Drug“Any substance that brings about a change in biologic function through its chemical actions”

Dose

“The amount of a drug to be administered at one time”

Mechanism of Action

“The ways by which drugs can produce therapeutic effects”

Indications

“The reasons for administering a medication or performing a treatment”

Contra-indications

“Factor that prevents the use of a medication or treatment (e.g., Allergies)”

Pharmacology, Definitions

Effects (therapeutic effect)

“The desired results of administration of a medication”

Side Effects (adverse effects)

“Effects that are harmful and undesired, and that occur in addition to the desired therapeutic effects”

Pharmacology, Definitions

Onset“The time it takes for the drug to elicit a therapeutic response”

Duration“The time a drug concentration is sufficient to elicit a therapeutic response”

The Role of Nurses in Relation to Pharmacology

Nurses share information with other health care professionals to provide the most effective medication regimen for the patient

Nurses play an active role in drug administration

Nurses contribute to the planning and modification of drug therapy from their assessment of patient factors and evaluation of progress or problems occurring during drug therapy

In addition to: the role in patient education and compliance

Nurses have to follow the “Five Rights” of Medication Administration

1. Right drug

2. Right dose

3. Right time

4. Right route

5. Right patient

Drug Sources1. Plant Sources: Obtained from plant parts or products. Seeds, stem,

roots, leaves, resin, and other parts yield these drugs. Examples include digoxin from digitalis and morphine from opium.

4. Mineral Sources: Some drugs are prepared from minerals, for example, lithium carbonate (an antipsychotic), MgSO4 (a laxative)

2. Animal Sources: Glandular products from animals are used, such as insulin and thyroid.

5. Synthetic Sources: Laboratories duplicate natural processes, and may modify the products. Frequently this can eliminate side effects and increase the potency of the drug. Examples include sulfonamides, and aspirin.

6. Recombinant proteins: Proteins that are synthesized by expression of cloned genes in recombinant cells, such as interferons, antibodies

3. From micro-organisms (fungi, bacteria) Penicillin was discovered by Alexander Fleming in 1928 as a product of penicillium notatum (a mold growing in his lab)

Brand or trade name (proprietary) is developed by the company requesting approval for the drug and identifies it as the exclusive property of that company. Example 1: Metrogyl® is the trade name for metronidazole. Example 2: Reglan® is the trade name for Metoclopramide. Example 3: Amoxil® is the trade name for amoxycillin. Example 4: Celebrex® is the trade name for Celecoxib.

Drug Nomenclature

Example 1: the chemical name 2-methyl-5-nitroimidazole-l-ethanol is metronidazole. The word methylnitro is condensed to metro and ni-dazole is due to its imidazole ring

Example 2: Metoclopramide is the condensed form of the word methoxychloroprocainamide: where Me is retained and th is written as t; chloro is written as clo: and procainamide is written as pramide

Chemical name represents the exact description of the drug’s chemical composition

Generic name (non-proprietary) - simpler than the chemical name and - derived from the chemical name itself - easier to remember

B. Basic concepts in Pharmacology -Drug-Body Interactions

-Drug Receptors

- Drug Receptor Interactions

Overview

A. Introduction -Definitions

-Drug Sources

-Drug Nomenclature

Pharmacokinetics (in Greek: "pharmacon" meaning drug, and "kinetikos" meaning putting in motion)

The study of the movement of drugs in the body, including the processes of absorption, distribution, metabolism and excretion (ADME)

The drug should be in an adequate concentration at the site of action to produce its effects. This depends on ADME.

Pharmacokinetics

Pharmacodynamics The study of the action or effects of drugs on living organisms

Pharmacokinetics vs Pharmacodynamics

What the drug does to the bodyWhat the body does to the drug

Drug-Body Interactions

Receptor/Binding site “A specific protein in either the plasma membrane or interior of a target cell with which a ligand/drug combines” It must be selective in choosing ligands/drugs

to bind To avoid constant activation of the receptor by promiscuous binding of many different ligands (drugs)

It must change its function upon binding in such a way that the function of the biologic system (cell, tissue, etc) is altered This is necessary for the ligand (drug) to cause a pharmacologic effect

Drug Receptors

Receptor/Binding site “A specific protein in either the plasma membrane or interior of a target cell with which a ligand/drug combines” It must be selective in choosing ligands/drugs

to bind To avoid constant activation of the receptor by promiscuous binding of many different ligands (drugs)

It must change its function upon binding in such a way that the function of the biologic system (cell, tissue, etc) is altered This is necessary for the ligand (drug) to cause a pharmacologic effect

Drug Receptors

Receptor/Binding site “A specific protein in either the plasma membrane or interior of a target cell with which a ligand/drug combines” It must be selective in choosing ligands/drugs

to bind To avoid constant activation of the receptor by promiscuous binding of many different ligands (drugs)

It must change its function upon binding in such a way that the function of the biologic system (cell, tissue, etc) is altered This is necessary for the ligand (drug) to cause a pharmacologic effect

Drug Receptors

The Lock and Key Model of Signal-Receptor Interaction

Ligands such as hormones or neurotransmitters (the"key") affect target cells by binding to specific receptors (the "lock”), which are often located in the cell membrane

This binding "unlocks" the cell's response, so that the hormone or neurotransmitter can exert its effects

Drug Receptor Interactions

Agonist

“A chemical messenger that binds to a receptor and triggers the cell’s response; often refers to a drug that mimics a normal messenger’s action”. For example, pilocarpine is a muscarinic receptor agonist because it can bind to and

activate muscarinic receptors

Antagonist

"A molecule that competes for a receptor with a chemical messenger normally present in the body. The antagonist binds to the receptor but does not trigger the cell’s response” For Example, atropine is a muscarinic receptor antagonist because it can bind to

muscarinic receptors but it does not trigger the cell’s response. In this way, it prevents binding of acetylcholine (ACh) and similar agonist drugs to the ACh receptor

Drug Receptor Interactions

Agonist Receptor

Agonist-Receptor

Interaction

Lock and key mechanism

Antagonist Receptor

Antagonist-Receptor

ComplexDENIED!

CompetitiveInhibition

Drug Receptor Interactions