General

Question 1

Define volume of distribution(VD)

Answer 1

Ratio of amount of drug in the body to its concentration in blood

Question 2

How can a drug have VD 1600/70kg

Answer 2

due to lipid solubility higher concentration in extravascular tissues than blood

Question 3

Examples of drug with high VD and low VD

Answer 3

High VD >70l/70kg- digoxin, diazepam, b blocker, morphine

Low VD- Lithium, warfarin, aspirin, antibiotics (amoxycillin, cephalexin, gentamicin) frusemide

Question 4

Difference B/W Efficacy and Potency

Answer 4

Potency- Concentration of drug required to produce 50% of the drug effect.
Efficacy- Maximum effect of the drug regardless of dose.

Question 5

Phase1 and Phase2 reaction

What organ involved

Answer 5

Phase1- convert the parent drug to more polar metabolite by introduction or unmasking of functional group.
e.g oxidation, reduction
requires mixed function oxidases(MFO) located ER of liver and other tissues(lung, skin).
MFO-cytochrome P450 and NADPH cytochrome P450reductase

Phase2- forms highly polar conjugate by introduction of functional group to drug. e.g Glucoronidation, sulphation

Liver lung

Question 6

clearance

factors affecting drug clearance

Answer 6

measure of ability of body to eliminate a drug Cl= rate of elimination/concentration

Blood Flow
Specific organ function
dose and bioavailability

Question 7

difference b/w capacity ltd and flow dependent elimination

Answer 7

Capacity ltd is saturable (zero order kinetics)

Flow dependent is non saturable(1st order)

Question 8

First Pass Metabolism
Defination

Mechanism

Answer 8

Reduction in drug concentration reaching circulation after absorption mostly from oral route and some from rectal

occurs via liver metabolism, gut wall metabolism bile excretion, portal blood metabolism

Question 9

factors affecting absorption from oral route

Answer 9

First pass metabolism
Transit time
Absorption
Gut bacteria metabolism

Question 10

bioavailability

depends on

Answer 10

unchanged amount of drug reaching systematic circulation after been taken from any route.

rate of absorption
first pass metabolism

Question 11

first pass metabolism

Answer 11

reduction in amount if drug reaching sys circulation after oral ingestion due to gut metabolism, portal blood and liver metabolism, bile excretion

Question 12

half life

factors affecting

Answer 12

time taken for reduction of the amount of drug by one half during elimination or infusion

those that affect Vd- body mass, fat distribution, malnutrition, oedema
Those that affect CL: renal disease, cardiac disease(Co)

Question 13

variables affecting drug absorption

Answer 13

route
blood flow
nature of absorbing surface: surface area cell membrane thickness
drug solubility- ionised(water soluble) unionised (lipid sol)

Question 14

zero order kinetics

Answer 14

constant rate of elimination irrespective of drug concentration but saturable.e capacity limited

Question 15

first order kinetics

Answer 15

rate of elimination is dependent on amount of drug not saturable

Question 16

clearance

Answer 16

Ratio of elimination of drug from the body to its concentration in blood

Question 17

Flow dependant elimination

Answer 17

rate of drug eliminated is dependant on amount of drug within the blood reaching the tissue
eg lignocaine, morphine