BAMS-Pharmacology Flashcards
What does a local anaesthetic do?
This reduces pain awareness and acts on nerve ion channels to block propagation.
Why do many local anaesthetics require adrenaline?
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.
What are analgesics?
These are drugs used to reduce pain or inflammation.
Discuss Paracetamol?
A painkiller which has little inflammatory action. The dosage is 500mg pills with a max of 8 a day.
Discuss NSAIDs?
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)
Discuss Corticosteroids?
These reduce inflammation but do not address the cause. Note: You might want inflammation to fight the infection.
What are Anxiolytics?
Drugs that reduce anxiety e.g. Diazepam.
Discuss diazepam’s effect?
It sticks to GABA receptors. These last longer because the metabolised form still works. (It lasts 24 hours in the body)
Compare hyperthyroidism and hypothyroidism?
Hyperthyroidism = too much thyroid hormone. Hypothyroidism = not enough thyroid hormone.
Compare Pharmacokinetics to pharmacodynamics?
Pharmacokinetics refers to what the body does to drugs Pharmacodynamics refers to what the drugs do to the body (D for drug).
How can drugs be administered?
Orally
By injections (Intravenous/ intramuscular/ subcutaneous)
Inhalation
What factors affect oral absorption and why?
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)
What is the first pass metabolism?
When you swallow a pill:
- The pill goes to the GI tract
- All blood from the GI tract drains to the hepatic portal vein which drains to the liver.
- The drug passes through the liver BEFORE it reaches systemic circulation.
Why is the first pass metabolism a disadvantage?
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.
Discuss the effect of first pass metabolism on injections
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
Why do we need to consider Patient liver function when deciding drug dosage?
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)
What is bioavailability?
The proportion of an injested drug that is available for clinical effects.
First pass metabolism/ Poor aborption/ destruction in the GUT can affect this.
What is the volume of distribution?
How much of the body the drug is diluted into
e.g. vascular/ tissues/ CNS
Discuss the phases of drug metabolism?
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.
How does drug excretion affect dosage?
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)
Compare the compartment models used to describe drug distribution.
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.
What is the plasma half life and why is it useful?
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.
Compare first order kinetics to zero order kinetics
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.
Why are repeat doses given?
So that the drug administration balances out drug elimination to maintain a concentration of drug in the plasma.
