Pharmacodynamics

Question 1

What is Pharmacodynamics

Answer 1

It is the sceince of how a drug works at its site of action (the biological affect the drug will have)

Most drugs will either interact at a cell receptor or interfere with an enzyme system to cause an effect.

Interaction between cell receptor and drug requires a Ligand (Molecule that transmits signal betwwen or within cells)

Question 2

What is an antagonist drug

Answer 2

A drug that binds to a receptor without activating it. It blocks the receptor or the effect of a substance that normally occupies the space.

E.G A Local Anesthetic such as Lidocaine binds to sodium channel in a nerve membrane, preventing signal transmission

Question 3

What is an Agonist Drug

Answer 3

A drug that binds to a receptor producing a similar response to the inteded receptor.
It mimics the basic endogenous system.

Question 4

What are the different forms of Agonist

Answer 4

Full Agonist - refers to a drug that binds to a given receptor and can stimulate the same maximal affect or efficacy as the basic endogenous substance EXAMPLE - MORPHINE

Partial Agonist - Refers to a drug that binds to a given receptor and the receptor is only partially activated to below the maximal affect or efficacy EXAMPLE - BUPRENORPHINE

Question 5

Explain how platelets work in order to understand how aspirin is beneficial as an anti platlet / anti coagulant drug

Answer 5

Platelets are recruited to the site of injury due to exposed molecules as a result of tissue damage.

Interaction between the exposed molecules (collegen, Von willerbrand factor) and receptors in the platelet membrane change the platelet from its resting state to its active dendretic form

The active platelet releases adp and Thromboxine2 TxA2 which causes platelet aggregation recruting more platelets to the site of injury forming a platelet plug

Following this the coagulation cascade is triggered and inturn the formation of thrombin. Thrombin stimulates fibrin which stabalises the clot

Question 6

What are Prostaglandins

Answer 6

Lipids with hormone like properties, that are used for:
* Gastric protection (control gut acid production)
* Haemostasis (Blood clotting)
* Pain and Inflamttion

Question 7

Explain the Pharmacodynamics of Aspirin

Answer 7

Aspirin acts to inhibit the production of Prostaglandins

Arochidonic acid is produced by the Prostaglandins

An enzyme called COX1 converts Archidonic acid into TxA2 (stimulates Platelet agregattion)

Asprin irriversibly inhibits the COX1 enzymes stopping Txa2 from inducing platelet aggregation

NOTE Asprin also inhibts COX2 but its antiplatlet action is a result of inhibiting COX1

The dosage amount would determine the desired affect higher dose 300mg and above would inhibit cox 1 and 2