Module 5 - Pharmacodynamics and Pharmacokinetics

any chemical substance that affects living processes

Drug

component of tissue where drug can bind

Receptor

establish and maintain for a certain time, an effective concentration of the drug in the immediate vicinity of its site of action.

Biophase

Type of Dose-Response Relationship

• Graded dose-response relationship

• Quantal dose-response relationship

as the dose of a drug is increased, the magnitude or intensity of response also increased

Graded dose-response relationship

magnitude / intensity of response is proportional to the effective drug concentration

Graded dose-response relationship

as the dose of the drug is increased, the number or proportion of animal exhibiting a response is also increased

Quantal dose-response relationship

Quantal dose-response relationship is an _____________ response

all-or -nothing response

ED50 =

median effective dose

dose that will produce response in 50 % of the animal population

ED50

LD50 =

median lethal dose

dose that will produce death in 50 % of the animal population

LD50

a drug that possesses affinity for a particular kind of receptor, and the ability to cause a change in this receptor that give rise to an observable effect

Agonist

any drug that counteracts the effect of an agonist.

Antagonist

Type of Antagonists

• Pharmacologic antagonism

  • Competitive antagonist

• Non-competetive antagonist

• Chemical antagonist

antagonism that interact with the receptor or any component of the receptor or any component of the effector mechanism to inhibit the action of the agonist.

Pharmacologic antagonism

antagonist compete for the same receptor with the agonist, which both have affinity.

Competitive antagonist

prevents the agonist from producing its effect at a given receptor site, it also inhibit any component of the stimulus (allosteric site)

Non-competetive antagonist

Competitive antagonist example

Spironolactone (Aldosterone antagonist)

Non-competetive antagonist example

Glutamic acid / glycine / serine (Dextromethorphan antagonist)

the antagonist does not cause its effect by interaction with tissue receptor sites, but interact with agonist itself.

Chemical antagonist

Chemical antagonist example

• Protamine (basis drug)

• Heparin (acidic drug)

A type of antagonism where a drug counters another drug by chemical reaction or neutralization without receptor binding.

Chemical antagonism

Example of chemical antagonism involving arsenic or lead

Calcium sodium edetate forms insoluble complexes with arsenic/lead

Properties/Characteristics of Drugs

• Affinity

• Efficacy (intrinsic activity)

• Selectivity

• Specificity

• Potency

• Drug safety

tendency of a drug to combine with a particular kind of receptor

Affinity

characterized by the maximal effect the drug can produce

Efficacy (intrinsic activity)

drug are usually described y their most prominent effect

Efficacy (intrinsic activity)

Capacity to preferentially produces a particular effect

Selectivity

Characteristic effect of a drug that is produced at a lower dose than those required to elicit other response.

Selectivity

Example of efficacy

Xylazine = sedative

Example of Selectivity

emetic

when all the effects produced by a drug are due to a single mechanics of action.

Specificity

refers to the dose that must be administered to produced a particular effect of given intensity

Potency

Paracelsus observed that all substances are?

poison, for there is nothing without a poisonous qualities.

It is only the ____ which makes a substance poisonous.

dose

obtained from the ratio of the median lethat dose to the median effective dose

Therapeutic index

derived from the ratio of the extremes

Certain safety factor

Drugs that do not directly need a receptor to produce an effect

• 1.Inhalant anesthetics

• 2.Osmotic diuretics

• 3.Saline cathartics

• 4.Antacids

• 5.Urinary acidifies

• 6.Urinary alhalinizers

• 7.Antiseptics