Pharmacology

Question 1

What is a ligand?

Answer 1

Any substance that binds to a receptor i.e. drugs, hormones, neurotransmitters

Question 2

Define affinity of a ligand to a receptor

Answer 2

The strength of attraction of a ligand to a receptor. It does not affect the effect the ligand has when bound to the recpetor

Question 3

Define selectivity (of a ligand)

Answer 3

The capacity of a ligand to produce a specific effect (rather than a broad spectrum of effects)

Question 4

Define specificity (of a ligand)

Answer 4

A ligands capacity to bind to a specific type of receptor only

Question 5

What is lag time?

Answer 5

The time between administration of a drug and the appearance of pharmacological effects

Question 6

Define full agonist

Answer 6

Full activation of a receptor - the same effect as the endogenous neurotransmitter

Question 7

Define a partial agonist

Answer 7

A ligand that is an agonist at a receptor but doesn’t produce the full effect that an endogenous neurotransmitter would. E.g. buprenorphine at mu receptors. However it has a high affinity for mu receptors

Question 8

Define an antagonist

Answer 8

A ligand that binds to a receptor but does not activate it. They can be competitive or non competitive. Flumazenil is a competitive antagonist

Question 9

What is the difference between competitive and non competitive antagonists?

Answer 9

Competitive antagonists bind to the same receptor site as the agonist and can be displaced with higher concentrations of the agonist.
Non-competitive antagonists bind to the same spot or a different site on the receptor and are not displaced by increasing the concentration of the agonist - they are harder to shift!

Question 10

Define a reverse agonist

Answer 10

A ligand that binds to a receptor and produces the opposite effect normally produced by the agonist ligands for that receptor. Eg if the agonist effect provides analgesia then the reverse agonist produces pain

Question 11

What is an agonist-antagonist?

Answer 11

A ligand that has an agonist effect on some receptors and antagonist on others. E.g. butorphanol is an agonist at kappa receptors but an antagonist at mu receptors.

Question 12

What is the significance of a drug being lipophilic or hydrophilic?

Answer 12

Lipophilic drugs have a faster onset and shorter duration of action because they pass through cell membranes more easily. E.g. fentanyl is more lipophilic (with shorter duration) than morphine which is more hydrophilic. This allows morphine to stay in the epidural space for longer.

Question 13

Local anaesthetics are sodium channel blockers, how does this work?

Answer 13

Local anaesthetics such as lidocaine prevent generation of action potentials, via influx of Na ions through Na channels into the neve cell

Question 14

How do GABA receptors work in regard to pain?

Answer 14

GABA is a neuro inhibitory receptor. It reduces CNS activity by causing hyperpolarization of the neuron.

Question 15

How do NMDA receptors work?

Answer 15

Glutamate is the NT. Enough nociceptive stimulation and the Mg2+ plug is removed and the receptor is activated - leading to central sensitisation

Question 16

Where are alpha adrenoceptors found and what is their function?

Answer 16

Alpha receptors are stimulatory except for those found on intestinal smooth muscle.
They cause vasoconstriction in vascular smooth muscle.
On the heart (stimulatory) A1 cause vasoconstriction and positive inotropy. A2 cause vasoconstriction, negative inotropy and reduced HR.

Question 17

Where are beta adrenoceptors found and what is their function?

Answer 17

Beta receptors are inhibitory except for those on the cardiac muscle which produce positive chronotropic and inotropic effects. They have inhibitory (relaxing) effects on the bronchial & vascular smooth muscle (vasodilation) & GI & genito-urinary tissues

Question 18

How does adrenaline and noradrenaline interact with alpha and beta receptors?

Answer 18

Noradrenaline has a more potent effect on alpha receptors than adrenaline (mix of a1 & a2), whilst adrenaline has a more potent effect on beta receptors than noradrenaline (HR & contractility).

Question 19

Define potency

Answer 19

The concentration of a drug required to obtain a pharmacological effect - the less drug needed to produce an effect, the more potent it is

Question 20

Define effective dose

Answer 20

The dose of a drug necessary to produce the desired effect in 50% of animals it is administered to

Question 21

Define lethal/toxic dose

Answer 21

The dose of a drug necessary to induce death/toxic effects in 50% of animals it is administered to

Question 22

Define therapeutic index

Answer 22

A measure of how safe a drug is - the higher the index, the more safe a drug is

Question 23

Define therapeutic index

Answer 23

A measure of how safe a drug is - the higher the index, the more safe a drug is

Question 24

Define total body clearence

Answer 24

A measure of how efficiently the body can eliminate a drug completely

Question 25

What is the first pass effect?

Answer 25

Drugs taken orally pass through the liver first with varying levels of metabolism before entering systemic circulation and reaching the target organ

Question 26

What is the second gas effect?

Answer 26

The ability of a low blood-gas solubility gas such as nitrous oxide (fast onset and recovery) to increase uptake of a more soluble inhalant such as isoflurane

Question 27

What is blood gas coefficient?

Answer 27

A ratio to describe how soluble an inhalant gas is in blood. The higher the BGC, the more soluble and the slower onset and recovery. The lower the BGC, the faster onset and recovery. Lower BGC gasses like N2O can give second gas effect to inhalants with higher BGC.

Question 28

What is bioavailability?

Answer 28

To what extent a drug enters the bloodstream and reaches the site of action to carry out the desired effect

Question 29

What is context sensitive half life?

Answer 29

Context sensitive refers to how long an infusion has been given for and half life is the time it takes for plasma concentrations to drop by 50%. I.e the time it takes a drug to wear off depending on how long you give it for.

Question 30

Define drug synergism

Answer 30

When the combined effect or two or more drugs is greater than the sum of the drugs individually.
E.g. alpha 2 agonists and opioids combined effects are better than the effects of them individually