Pharmacokinetics

Question 1

What must considered of drug is solid?

Answer 1

Solubility and acid stability in stomach

Question 2

Give sites of administration

Answer 2

Focal- eye,skin,inhalation
Enteral-sublingual, oral, rectal
Paraenteral- subcutaneous, intramuscular, intravenous, inhalation, transdermal

Question 3

Define oral bioavailability

Answer 3

The proportion of a drug dose taken orally that reaches the circulation in an unchanged form

Question 4

How can oral bioavailability be expressed?

Answer 4

Amount - area under curve of blood drug level vs time
Rate - rate of rise of drug level in blood

Area under curve oral over
Area under curve IV

Question 5

What is LD50

Answer 5

The maximum tolerated dose.

Lethal dose in 50% of the population

Question 6

What is ED50

Answer 6

The minimum effective dose

The drug concentration that produces an effective response in 50% of the population

Question 7

What is the therapeutic ratio

Answer 7

ED50

Question 8

What does a large therapeutic ratio indicate

Answer 8

Larger therapeutic window

Safer drug

Question 9

Advantage of slow release prep

Answer 9

Spend longer time in the therapeutic window.

Question 10

Describe first pass metabolism

Answer 10

Drug absorbed from the gut enters hepatic portal system.
Liver is main site of drug metabolism and contains main enzymes, metabolising drug before it gets to systemic circulation.

Question 11

How can first pass metabolism be avoided

Answer 11

Paraenteral route
Sublingual route
Rectal route

Question 12

What is The volume of distribution

Answer 12

The theoretical volume into which the drug has distributed assuming this is instantaneous

Question 13

What is the erect of a clasS II precipitant drug

Answer 13

When taking an object drug the precipitant drug will displace it on albumin and plasma proteins causing a greater free concentration of object drug

Question 14

Give two forms of drug elimination and organs

Answer 14

Metabolism liver

Excretion kidneys

Question 15

Describe metabolism of drugs

Answer 15

Phase I - oxidation, reduction and hydrolysis to expose reactive group cytochrome p450 and NADPH
Phase II - conjugation to form water soluble complex with glucoronide, sulphate,

Question 16

Describe kidney excretion

Answer 16

Only free unbound drug can be filtered
Drugs actively secreted into PCT
Passive resorption of lipid soluble, unionised drug in DCT

Question 17

For weak acids, how do you increase excretion

Answer 17

Make urine alkaline

This will ionise the drug causing less resorption and more excretion

Question 18

How do you increase excretion of weak base

Answer 18

Make urine acid

This will ionise the base and result in less resorption and more excretion.

Question 19

How many half lives does it take to reach steady state

Answer 19

5

Question 20

How does drug plasma level change with dose in 1st order kinetics

Answer 20

Constant increase
Straight line
Elimination is proportional to drug plasma concentration.
Half life is constant.

Question 21

How does las a drug level change with dose in 0 order kinetics

Answer 21

Curve upwards as at high dose ther is very high plasma drug conc as elimination does not increase, it remains at same rate.
Steady state reached in 5 half lives

Question 22

How does warfarin act?

Answer 22

Vitamin K antagonist
Cut K required for carboxylate on of glutamate residues on prothrombin
Gla residues allow for congregation of clotting factors.
Warfarin prevents this

Question 23

Give 2 parts of the pharmaceutical process

Answer 23

Formulation of drug

Site of administration