BAMS-Pharmacology

Question 1

What does a local anaesthetic do?

Answer 1

This reduces pain awareness and acts on nerve ion channels to block propagation.

Question 2

Why do many local anaesthetics require adrenaline?

Answer 2

The locals are vasodilators so increase blood flow which moves the anaesthetic away from its target. Adrenaline is a vasoconstrictor so narrows the blood vessels and prolongs the anaesthetic effects.

Question 3

What are analgesics?

Answer 3

These are drugs used to reduce pain or inflammation.

Question 4

Discuss Paracetamol?

Answer 4

A painkiller which has little inflammatory action. The dosage is 500mg pills with a max of 8 a day.

Question 5

Discuss NSAIDs?

Answer 5

They are Anti-inflamatory (reduce inflammatory mediator production) These inhibit prostaglandin synthesis to make platelets less sticky, causing more bleeding. e.g. Aspirin = Ibruprofen < Diclofenac. (effective)

Question 6

Discuss Corticosteroids?

Answer 6

These reduce inflammation but do not address the cause. Note: You might want inflammation to fight the infection.

Question 7

What are Anxiolytics?

Answer 7

Drugs that reduce anxiety e.g. Diazepam.

Question 8

Discuss diazepam’s effect?

Answer 8

It sticks to GABA receptors. These last longer because the metabolised form still works. (It lasts 24 hours in the body)

Question 9

Compare hyperthyroidism and hypothyroidism?

Answer 9

Hyperthyroidism = too much thyroid hormone. Hypothyroidism = not enough thyroid hormone.

Question 10

Compare Pharmacokinetics to pharmacodynamics?

Answer 10

Pharmacokinetics refers to what the body does to drugs Pharmacodynamics refers to what the drugs do to the body (D for drug).

Question 11

How can drugs be administered?

Answer 11

Orally

By injections (Intravenous/ intramuscular/ subcutaneous)

Inhalation

Question 12

What factors affect oral absorption and why?

Answer 12

Lipid solubility and ionisation as a drug needs to be lipid soluble to be absorbed.

Drug formulation as some drugs will take longer to dissolve than others e.g. coated pellets.

The patient’s GI system as GUT problems can affect drug absorption.

Interactions with other substances (other drugs)

Question 13

What is the first pass metabolism?

Answer 13

When you swallow a pill:

1. The pill goes to the GI tract
2. All blood from the GI tract drains to the hepatic portal vein which drains to the liver.
3. The drug passes through the liver BEFORE it reaches systemic circulation.

Question 14

Why is the first pass metabolism a disadvantage?

Answer 14

The drug is metabolised in the liver. This means you lose a concentration of the drug as it is activated and absorbed before you make it to circulation.

Question 15

Discuss the effect of first pass metabolism on injections

Answer 15

First pass metabolism only applies to the GUT so Injections bypass this.

The drug is where it needs to be, allowing the predictions of plasma levels in the blood

Question 16

Why do we need to consider Patient liver function when deciding drug dosage?

Answer 16

Normal liver function may require a larger dosage to be given (as liver will reduce the drug concentration before it reaches circulation)

Abnormal liver function will require the dose to be altered as the patient’s first pass metabolism will be less effective (too large a conc in the patient)

Question 17

What is bioavailability?

Answer 17

The proportion of an injested drug that is available for clinical effects.

First pass metabolism/ Poor aborption/ destruction in the GUT can affect this.

Question 18

What is the volume of distribution?

Answer 18

How much of the body the drug is diluted into

e.g. vascular/ tissues/ CNS

Question 19

Discuss the phases of drug metabolism?

Answer 19

Phase1- Drug undergoes reactions that change it’s confirmation. (oxidation/ reduction/ hydrolysis)

Phase2- Conjugation where the drug is added to another drug to increase the drug effect.

Question 20

How does drug excretion affect dosage?

Answer 20

Reduced renal function or liver failure in patients requires a smaller dose as the patient cannot get rid of the drug as easily (Through urine or bile)

Question 21

Compare the compartment models used to describe drug distribution.

Answer 21

Single compartment model is when the drug is evenly distributed throughout the body.

Two compartment model is when the drug goes to tissues with a larger blood flow first before going to the whole body.

Question 22

What is the plasma half life and why is it useful?

Answer 22

Plasma half life is how long it takes for half of the drug to be removed from the body.

It is useful for measuring clearance.

Question 23

Compare first order kinetics to zero order kinetics

Answer 23

First order kinetics describes drug elimination or absorption by passive diffusion. More drug means it is removed from the body quicker.

Zero order kinetics A constant amount of drug is eliminated. this relies on the prescence of a mechanism for the drug e.g. drinking & becoming drunk.

Question 24

Why are repeat doses given?

Answer 24

So that the drug administration balances out drug elimination to maintain a concentration of drug in the plasma.

Question 25

What happens if the dose is too frequent or too infrequent?

Answer 25

If the dose is taken too frequently, plasma levels become toxic

If the dose is taken too infrequently, there will low plasma levels so there is no drug effect.

Question 26

In practice, how would you deal with a patient feeling heart pain?

Answer 26

You use a GTN spray, to avoid first pass metabolism.

This should cause thepain to go away unless it’s a heart attack.

Question 27

What do we need to know to decide a dosage schedule?

Answer 27

We need to know:

• About the drug (i.e. the half-life)
• About the patient’s clearance (Liver and renal function)

Question 28

How do you give a patient adrenaline in an emergency?

Answer 28

Intramuscularily

Question 29

Discuss the dosage of Amoxicillin?

Answer 29

It is 250mg pills given 3 times a day.

Question 30

Calculate the maximum safe dosage of 1% Lidocaine.

for a 70kg man.

The safe dosage is 3mg per kg

& how many LA cartridges can you use?

Answer 30

So the save dosage for a 70kg man is 210mg

(there is 2.2mls in a standard LA cartridge)

In 1% 1000mg per 100ml

10mg per ml

20mg per 2ml solution.

Therefore, you can’t do more than 9/10 cartridges or local anaesthetic toxicity!