How drugs work

Question 1

Cellular mechanisms of drug action

Answer 1

Modification of cell membrane structure and function, e.g. Ca-channel blockers inhibit entry of Ca into cells.

Enzyme inhibition, In the host animal or in invading pathogens

Receptor-mediated effects

Question 2

Non-cellular mechanisms of drug action

Answer 2

Physical effects, e.g.: Protective, lubricant properties etc.

Chemical reactions e.g. Neutralisation of HCl by antacids

Physicochemical mechanisms e.g. Antifoaming agents, surfactants

Modification of the composition of body fluids

Question 3

Drug response may characterized as either:

Answer 3

Graded (continuous) – changes in blood pressure, hormone concentration, can be studied in an individual animal;

Quantal (present or absent; composed of discrete units; steps as opposed to continuous)

– prevention of seizures, induction of parturition, can be investigated in a group of animals.

Question 4

Partial agonist action:

Answer 4

acts at a receptor but produces less than maximal effect.

If a partial agonist occupies a significant fraction of the available receptor population, it antagonizes the action of the agonist.

Question 5

Down regulation:

Answer 5

continual stimulation of cells by an agonist may result in desensitization (down regulation) – concentration of agonist should be increased.

Question 6

Up-regulation:

Answer 6

additional receptors can be synthesized in response to chronic receptor antagonism.

After subsequent administration of an antagonist, more receptors are available, causing super-sensitivity.

Question 7

Signaling mechanisms and drug action

Answer 7

Induction of synthesis of specific proteins by intracellular receptors that regulate gene expressions.

Regulation of gated ion channels in the plasma membrane.

Regulation of plasma membrane enzymes.

Calcium entry into the cells.

Accumulation of multiple intracellular second messengers.

Stimulation of plasma membrane-bound protein kinases.

Question 8

define Excipients

Answer 8

An excipient is a constituent of a medicine other than the active substance, added in the formulation for a specific purpose.

While most excipients are considered inactive, some can have a known action or effect in certain circumstances.

Question 9

Factors that modify drug effects and dosage form

Answer 9

Drug and dosage form
Medical and medication errors
Feeding
Drug interactions
Inter- and intraspecies differences
Within species differences (age, sex, disease)

Question 10

ADR

Answer 10

ain’t doin right

Adverse drug reactions: any response to a drug that is noxious and unintended and that occurs at doses used in animals for prophylaxis, diagnosis or therapy.

Question 11

Pseudoallergic drug reactions

Answer 11

Drug reactions that do not have an immunological basis.

Anaphylactoid reactions, do not require prior exposure to the drug.

Occur most frequently when a drug is given rapidly intravenously.