pharmacology concept 2

8/4/2019 Pharmacology Concept 2

1/22

Compiled by Venina Navuta

22/8/11

Pharmacology Concepts 2


2/22

Terminology

Drug: substance or chemical thatalters physiological or biochemicalpattern. Used in diagnosis, prevention

or treatment.Drug action: interaction of drug withspecific sites cells, receptors or at sub

cellular level. (Usually Invisible)Drug effect: consequences of drug

actions leads to notable change like


3/22

Agonist: has affinity to specificreceptors where it exhibits its action

(intrinsic activity)

Antagonist: binds to the receptors of

agonist and lacks activityPartial agonist: has some less affinity

and less intrinsic activity. Has same

actions as agonist but of less degreeat the same time blocks the receptor

for agonist to bind.


4/22

Efficacy the ability to producearesponse

Potency the dose range over which a

response is produced

Tachyplaxis a decrease in the responseto a drug due to previous exposure tothat drug

Therapeutic index the ratio between thetoxic dose and the therapeutic dose of adrug used as a measure of the relative

safety of the drug for a particular


5/22

Dose-Response Relationship

Relationship between the size of anadministered dose and the intensity ofthe response produced

The dose-response relationships formost drugs are graded i.e. responsegets more intense with increasingdosage

Because they are graded, therapeuticeffects can be adjusted to fit theneeds of each patient


6/22

Types of drug responses

For drug to act should reach a criticalconcentration at its site of action

Above critical concentration. Drug

exhibits response related to dose up tocertain range till its maximumtherapeutic response is reached

Once maximum drug response isreached rise in dose has noenhancement in response but leads to

increase in toxic effects.


7/22

3 Phases of Dose-response

relationship

Phase 1 occurs at low doses, too low toelicit a measurable response

Phase 2- an increase in dose elicits a

corresponding increase in the response.This phase is where dose-responserelationship is graded

Phase 3a point where an increase indose is unable to elicit a further increasein response, the curve flattens


8/22

Maximal Efficacy & Relative Potency

Maximal efficacy

the largest effect that a drug canproduce

Indicated by the height of the dose-response curve

drug with high maximal efficacy isnot always more desirable than adrug with lower efficacy


9/22

Relative Potency

Amount of drug that we must give inorder to elicit an effect

Potent drug is one that produces its

effects at low dosesPotency and efficacy are 2

independent qualities.


10/22


11/22

Receptors through which drugs actare normal points of control ofphysiologic processes

The two main functions of receptorsare: ligand (drug) binding, and,activation of effector mechanism


12/22

Under physiologic conditions, receptorfunction is regulated by molecules

supplied by the body

All that drugs can do at receptors ismimic or block the action of bodys

own regulatory molecules


13/22

Drugs cannot give cells new function

but can only alter the rate of pre-existing processes

Drugs produce their therapeuticeffects by helping the body use itspre-existing capacities to the pts best

advantage. Medications simply help

body to help itself


14/22

In theory, it should be possible to

synthesize drugs that can alter rate ofany biologic processes for whichreceptors exist

Ligand binding is determined byaffinityand specificity

Affinity describes how strongly thedrug and receptor interact.

Specificity refers to selectivity areceptor has for a drug.


15/22

Agonists & Antagonists

Agonists bind to receptor sites &activate receptor mechanisms(elicit biological responses).

Antagonists bind to receptors

but do not activate effectormechanisms (do not producebiological effects)


16/22

Effectors

Transduce drug-receptor interactionsinto cellular effects.

1. Intracellular receptors

2. Transmembrane receptors

3. Ligand-gated ion channels

4. Receptors coupled to 2ndmessenger systems


17/22

Individual Variations in Drug

Responses

In order to maximize beneficial drugresponses & minimize harm, we mustadjust therapy to account for sources

of individual variation small pts need smaller doses than

large pts

Dosage adjustments made to accountfor size are often based on bodysurface area, rather than simply onbody weight


18/22

Infants & the elderly are more

sensitive to drugsTherapeutic & adverse effects differ

between males & females

Kidney disease can decrease drugexcretion

Liver disease can reduce drug

metabolism


19/22

When pts become tolerant to a drug,

dosage must be increased to maintainbeneficial effects

Placebo effect is `the component of a

drug response that can be attributedto psychologic factors


20/22

Genetic factorsespecially genetically

determined rates of drug metabolism-can be a source of individual variation

Poor patient compliance is a major

source of individual variation.


21/22

Classification of Drugs

Adrenergic

Dopaminergic

Cholinergic Drugs

Anticholinergic Drugs

Calcium Channel Blockers Ace Inhibitors


22/22

Angiotensin II Inhibitors

Opioids analgesics Proton Pump Inhibitors

Corticosteroids

Steroids

pharmacology concept 2

Documents