Pharmacology for Nursing 1. Munir Gharaibeh, MD, PhD, MHPE Department of Pharmacology School of Medicine The University of Jordan

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Pharmacology for Nursing 1

Munir Gharaibeh, MD, PhD, MHPE Department of Pharmacology

School of Medicine

The University of Jordan

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Pharmacology

Is the science of drugs. It is the

knowledge of history, sources, physical and chemical properties, absorption,

distribution, excretion,

biotransformation, actions and therapeutic uses of drugs.

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Pharmacy

Is the branch of health sciences dealing with the preparation, dispensing, and

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Toxicology

Is the part of pharmacology which

deals with adverse effects of drugs and the toxic effects produced by

household, environmental and industrial chemicals.

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Drug

A chemical that affects the living processes. It modifies an already

existing function, and does not create a new function.

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Drug-Body Interactions

The interactions between a drug and the body are conveniently divided into two classes.

The actions of the drug on the body are termed

pharmacodynamic processes .

The actions of the body on the drug are termed

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Pharmacodynamic processes

.

These properties determine the

group in which the drug is

classified, and they play the major

role in deciding whether that group

is appropriate therapy for a

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Pharmacokinetic processes

.

These processes govern the

absorption, distribution, and

elimination of drugs and are of

great practical importance in

the choice and administration of

a particular drug for a particular

patient, e.g., a patient with

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Drug Receptors & Pharmacodynamics

Most drugs act by associating with

specific macromolecules to alter their

biochemical or biophysical activities.

Receptors

)

تلابقتسملا

)

are

the

components of the cell or organism

that interact with a drug to initiate

chain of events leading to the drug's

effects.

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Drug Receptors & Pharmacodynamics

Many drug receptors have been isolated and characterized in detail, thus opening the

way to precise understanding of the molecular basis of drug action.

The receptor concept has important

practical consequences for the development of drugs and for arriving at therapeutic

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Drug Receptors & Pharmacodynamics

Receptors largely determine the

quantitative relations between dose (or

concentration) of the drug and

pharmacologic effects

.

The total number of receptors limits

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Relations between drug concentration and drug effect

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Relations between drug concentration and receptor-bound drug

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Drug Receptors & Pharmacodynamics

Receptors are responsible for selectivity of

drug action .

The molecular size, shape, and electrical

charge of a drug, determine how good it will bind to a particular receptor.

Accordingly, modifications in the chemical structure of a drug can dramatically

increase or decrease drug affinity for

different classes of receptors, with resulting alterations in therapeutic and toxic effects.

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Drug Receptor Interactions

Agonists

act at the agonist binding site(Receptors) to initiate an action.

Competitive Antagonists or Inhibitors

act at

the agonist binding site, to produce no

action, but can inhibit the binding and action of the agonist.

Allosteric Activators

act at separate sites to increase the efficacy of the agonist or its

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Agonist-Antagonist Relationships

Competitive (or reversible) antagonist:

High agonist concentrations can overcome the inhibition by a competitive antagonist. Higher concentrations of the agonist will be required to produce a given effect

Irreversible (or noncompetitive) antagonist:

Produces irreversible changes in the

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Transmembrane Signaling

Mechanisms

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Transmembrane Signaling Mechanisms

1. Lipid-soluble drug crosses the plasma membrane

and acts on an intracellular receptor (which may be an enzyme or a regulator of gene transcription.

2. The drug binds to the extracellular domain of a transmembrane protein, thereby activating an enzymatic activity of its cytoplasmic domain

3. The drug binds to the extracellular domain of a transmembrane receptor bound to a separate protein tyrosine kinase, and activates it.

4. The drug binds to, and directly regulates the opening of an ion channel

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Types of Dose-Response Curves

Gradede(جردتم) Dose-Response Curve. Quantal Dose-Response Curve.

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Relations between drug concentration and drug effect

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Features of Graded Dose-Response Curves

Maximal Efficacy.

Potency.

Slope or Shape of the Curve.

Variability (Standard variation at each

point)

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Features of

Quantal Dose-Effect Curves

Responses are all or non.

Follows the Normal Frequency Distribution. If Cummulative--- Sigmoid curve

– Straight line for most of the line .

We can calculate the Therapeutic Index= LD50/ED50

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Quantal Dose-Effect Curves

Median Effective Dose (ED50): is the dose at which 50% of individuals exhibit the specified quantal

effect.

Median Toxic Dose (TD50): is the dose required to produce a particular toxic effect in 50% of animals.

Median Lethal Dose (LD50): is the dose required to produce death in 50% of the of the animals.

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Therapeutic and Toxic Effects of Drugs

Three posssibilities:

Both mediated by the same receptor-effector mechanism.

– i.e. toxicity is a direct pharmacologic extension of the therapeutic action of the drug.

Mediated by identical receptors but in

different tissues or by different pathways. Each mediated by different types of

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Possibilities of Drug Combinations

Antagonistic Effects Additive Effects.

Synergistic Effects. No effect.

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Drug Antagonism

Pharmacologic Antagonism:

– Drugs work on the same receptor.

– Competitive Antagonism.

– Noncompetitive antagonism.

Physiologic Antagonism:

– Drugs work on opposite physiological processes.

– E.g. Epinephrine in Anaphylaxis.

Chemical Antagonism: