ILA pharmacokinetics and dynamics

Question 1

In order to induce anaesthesia quickly what characteristics should the drug have in terms of its protein binding?

Answer 1

lowers the free concentration of a drug. Induction drug should have low protein binding to enable a high initial plasma conc

Question 2

In order to induce anaesthesia quickly what characteristics should the drug have in terms of its lipid solubility?

Answer 2

Greater lipid solubility of a drug enhances potency and enables more rapid diffusion through cell membranes / across BBB

Question 3

Explain in terms of the drug distribution of the intravenous drug why an additional volatile drug needs to be given as soon as the patient is asleep.

Answer 3

secondary drugs - when co-administered with local anaesthetic agents, may improve the speed of onset and duration of anaesthesia and counteract negative side effects of local anaesthetics - therefore lower dose needed

Question 4

give some negative side effects of local anaesthetics

Answer 4

myocardial depression, hypotension, bradycardia, heart block, ventricular arrhythmias

Question 5

define agonist

Answer 5

• a compound that binds to a receptor and activates it
• e.g. methadone

Question 6

define antagonist and give a common example

Answer 6

• a compound that reduces the effect of an agonist
• e.g. naloxone

Question 7

define a competitive antagonist and give a common example

Answer 7

a medication that reversibly binds to the same receptor site where an agonist binds, but it does not activate it - eg. naloxone

Question 8

define a non - competitive antagonist and give a common example

Answer 8

bind to the allosteric site and cause the shape of the receptor to alter in a way that the ligand can no longer recognise it as a binding site - eg. ketamine

Question 9

explain how amlodipine works as a drug target on ion channels

Answer 9

• CCB inhibits the movement of Ca2+ ions into vascular smooth muscle cells so inhibits contraction of cardiac muscle and vascular smooth muscle cells
• causes vasodilation and reduction in peripheral vascular resistance → lowering blood pressure
• also prevents excessive constriction in the coronary arteries

Question 10

explain how ACE-i work on enzyme receptors

Answer 10

inhibiting ACE in RAAS reduces angiotensin 2 production and therefore causes a reduction in blood pressure

Question 11

state how a carrier molecule works as a drug target

Answer 11

• drugs occupy the binding sites of polar molecules and ions or to allosteric sites to modulate movement of polar molecules and ions across cell membrane

Question 12

define the term bioavailability

Answer 12

the amount of an administered drug that reaches the systemic circulation

Question 13

define first pass metabolism

Answer 13

the concentration of the drug which is lost during absorption before reaching systemic circulation, usually when administered orally

Question 14

Roughly how much more oral morphine is required compared to IM Morphine?

Answer 14

double, oral bioavailability - 50% for oral morphine, eg. 10mg morphine orally is equivalent to 5mg IM/IV

Question 15

when must the dose of morphine be altered and why?

Answer 15

in renal impairment
- morphine is metabolised to morphine-3-glucuronide and morphine-6-glucuronide which is more potent and is renally excreted.
- cleared quickly with normal renal function, however in renal depression / failure, it causes build up, leading to respiratory depression

Question 16

state 3 physical properties of an ideal IV anaesthetic drug

Answer 16

1. Non-flammable, non-explosive at room temp
2. Stable in light
3. Liquid and vaporisable at room temperature
4. Stable at room temperature
5. long shelf life
6. Stable with soda lime, as well as plastics and metals
7. Environmentally friendly - no ozone depletion
8. Cheap and easy to manufacture

Question 17

state 3 biological properties of an idea IV anaesthetic drug

Answer 17

1. Pleasant to inhale, non-irritant, induces bronchodilatation
2. fast onset
3. high potency
4. Minimal effects on other systems
5. should be excreted ideally via the lungs, unchanged
6. Non-toxic to operating theatrepersonnel

Question 18

define pharmacokinetics

Answer 18

The effect that the body has on the drug e.g. metabolism

Question 19

define pharmacodynamics

Answer 19

The effect that the drug has on the body