9 Pharmacokinetics Flashcards Preview

Semester 2-M+R > 9 Pharmacokinetics > Flashcards

Flashcards in 9 Pharmacokinetics Deck (23)
Loading flashcards...
0
Q

Define ‘oral bioavailability’

A

The proportion of a drug given orally that reaches the circulation unchanged.

1
Q

What occurs in the ‘pharmaceutical process’?

A

Formulation of the tablets/liquid
Work out compliance (eg. once a day)
Work out best way to administer drug

2
Q

What is the ‘therapeutic dose’?

A

The maximum tolerated dose/ minimum effective dose

3
Q

What is the ‘therapeutic window’?

A

The range of drug concentrations that will have a therapeutic effect with minimal unwanted side effects

4
Q

What is’ first-pass metabolism’ and how can it be avoided?

A

Drugs administered orally are first exposed to the liver and may be metabolised before reaching the circulation. It is avoided by using different routes of administration eg. IV, injections

5
Q

What is the ‘volume of distribution’ of a drug?

A

The theoretical volume into which a drug is distributed to if it was distributed instantaneously

6
Q

How is the ‘volume of distribution’ worked out?

A

Extrapolation of plasma levels to zero time

7
Q

What is the effect of a drug having a high level of Protein Binding Drug Interactions?

A

The drug will have a small volume of distribution and therefore a low therapeutic value.

8
Q

What is a Class I drug? What can these drugs also be called?

A

A drug administered at a dose lower than the number of albumin binding sites. They can also be called object drugs.

9
Q

What is a Class II drug? What can these drugs also be called?

A

A Class II drug is a drug given at a dose greater than the number of binding sites so displaces the class I drug. They can also be called precipitants.

10
Q

What is the relationship between drug concentration and elimination rate in First Order Kinetics?

A

Rate of elimination is proportional to concentration of drug. A constant fraction of the drug is eliminated in a unit time.

11
Q

What is the relationship between drug concentration and elimination rate in Zero Order Kinetics?

A

The rate of elimination is constant and independent of drug concentration.

12
Q

How many half lives of a drug are required to reach a steady state during repeated drug administration?

A

5

13
Q

What is a ‘loading dose’?

A

An initial large dose given at the start of a course of treatment

14
Q

Name the two ways a drug is eliminated from the system

A

Metabolic- through the liver

Excretion- through the renal system

15
Q

What happens when a drug goes through Phase I of metabolism?

A

Reduction, Oxidation, Hydrolysis to inactivate the drug

16
Q

What happens when a drug goes through Phase II of metabolism?

A

It is made soluble so it can be excreted via the kidneys

17
Q

When are drug interactions especially important?

A

When the drug has a low therapeutic ratio
When the drug is being used at the minimum effective concentration
When drug metabolism follows zero order kinetics

18
Q

Give an example of a drug interaction

A

Eg. Phenobarbitone affects Warfarin

19
Q

When can drugs be excreted via the renal system?

A

When the drugs is in the free form

20
Q

What is the pK to the drug and why is this important in renal excretion?

A

The pK of a drug is the pH at which half of the drug is ionised and half is non-ionised. The non-ionised drug can pass through membranes easily so is reabsorbed. The ionised drug leaves the body in the urine.

21
Q

What affect does acidic urine have on absorption?

A

Increases absorption

22
Q

What affect does alkaline urine have on absorption?

A

Decreases absorption