Pharmacology

Question 1

Bioavailability

Answer 1

Amount of drug that reaches the systemic circulation from the site of administration compared to IV. (IV=100%, e.g. oral= 0-100%)

(fraction of dose reaching systemic circulation intact -bit that is absorbed etc )

Question 2

Bioequivalence

Answer 2

same drug but 2 different formulations.
Even though there may be different name n price, both formulations will attain same conc in blood/tissues in same timeframe.
No differences in therapeutic/adverse effects

Question 3

perfusion

Answer 3

process of delivering blood to capillary bed in biological tissue

Question 4

Distribution of drug n Vd

Answer 4

15 L – drug distributed throughout TBW

eg alcohol

Question 5

Loading dose

Answer 5

A loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose.

Question 6

Drug Clearance (CL)

Answer 6

The volume of plasma cleared of drug per unit time’ (units = volume / time)

Question 7

Ion trapping

Answer 7

weak electrolytes will tend to accumulate in the compartment in which they are most highly ionised- cos not able to cross membranes as easily wen ionised

Question 8

degree of ionisation

affects distribution of drug

Answer 8

ionised = ‘charged'=low lipid solubility
unionised = ‘uncharged'= good lipid solubility=can cross membrane more 

pKa=pH where 50% ionised / 50% unionised

Acidic drugs are well absorbed in acidic enviro
Basic drugs are well absorbed in basic enviro

Question 9

Binding of drugs to plasma proteins

Answer 9

drugs stuck to plasma protein=inactive, can’t cross membrane, blood brain barrier, be filtered by glomerulus
vs
free drugs= active! good :)

Question 10

isoforms/isoenzymes

Answer 10

families of enzymes that catalyse the same chemical reaction for many different types of drugs
eg (phase 1) cytochrome P450 monooxygenase

Question 11

xenobiotic

Answer 11

something not normally naturally produced by or expected to be present within that organism i.e. foreign

Question 12

enzyme induction

Answer 12

some drugs can increase activity/levels of the enzymes

that metabolise them, leading to interactions with other drugs metabolised by the same enzyme. eg rifampicin

Question 13

steady state

Answer 13

rate of entry equal to rate of elimination

Question 14

Plasma half-life (t1/2)

Answer 14

time taken for the amount of drug in the body to fall by half (measured through plasma conc)

Question 15

therapeutic index

Answer 15

toxic over desired

Question 16

first order kinetics

Answer 16

rate of elimination is proportional to plasma concentration (exponential curve)
– constant half-life.

Question 17

Zero order kinetics

Answer 17

rate of elimination is constant and independent of [plasma] (linear curve)
-half life proportional to [plasma]]

increasing dose will increase activity disproportionately

Question 18

half life n CL

Answer 18

half life decreases with increasiing CL

Question 19

half life with VD

Answer 19

increase half life increase VD

Question 20

half life

Answer 20

after 1 dose, time to eliminate drug is 4-5 half lives

4th- 6.25% left
5th- 3.125% left

Question 21

Rate of elimination

Answer 21

=CL x [plasma]

Question 22

maintenance dose rate (DR)

Answer 22

= CL x target [ ]

Question 23

LD (loading dose)=

Answer 23

Vd x target [plasma]

Question 24

enzyme induction

Answer 24

drugs that increase activity level of enzymes that metabolise them e.g. alcohol - can get drug interactions

Question 25

Hepatic metabolism phase 1

Answer 25

‘catabolism’
oxidation/reduction/hydrolysis i.e. adding oxygen or electron
to make drug more water soluble

use liver MICROSOMAL enzymes (cytochrome P450 enzymes)
may make drug toxic e.g. paracetamol

Question 26

hepatic metabolism phase 2

Answer 26

‘conjugation’
combine with endogenous molecule(e.g. glucuronide acetyl) to make drug more polar, water soluble enough for excretion in urine
use liver MICROSOMAL or CYTOSOLIC enzymes

Question 27

Vd=

Answer 27

dose/[plasma]

units= volume (L) /kg

Question 28

high VD=

Answer 28

lots of drug in tissues,

low amount in plasma

Question 29

low VD=

Answer 29

lots of drug in plasma

Question 30

VD formula rearranged

Answer 30

Dose (amount of drug in body)=VD x Plasma conc

Question 31

kidney

Answer 31

removes water soluble drugs

Question 32

liver

Answer 32

metabolism (breaks down) drug

Question 33

plasma protein

Answer 33

generally albumin and alpha-1 acid glycoprotein

Question 34

pharamcogenetics

Answer 34

study of how genetic differences influence the way patient respond to drug

Question 35

pharmacogenomics

Answer 35

use of genetic info to guide drug therapy - differences in response of individuals to drugs can be predicted by looking at their genotype

Question 36

cytochrome p-450

Answer 36

all genes encoding CYP1/2/3 family of P-450 enzymes are polymorphic