Pharmacology

Question 1

what is the minimum effective concentration (MEC)?

Answer 1

the concentration a drug must reach in plasma to be effective

Question 2

what is the maximum tolerated concentration (MTC)?

Answer 2

the concentration of a drug in plasma that will cause unwanted side effects

Question 3

how is a drugs therapeutic ratio (TR) calculated?

Answer 3

MTC/MEC

Question 4

do safer drugs have high or low TRs?

Answer 4

high

unsafe = low

Question 5

what is ED50?

Answer 5

the median effective dose of a drug

Question 6

what is TD50?

Answer 6

the median toxic dose of a drug

Question 7

what is LD50?

Answer 7

the median lethal dose of a drug

Question 8

when does a drug interaction occur?

Answer 8

when the effects of one drug are increased/decreased by the administration of another

Question 9

describe a pharmacodynamic drug interaction

Answer 9

drug A modifies the effect of drug B, without altering its concentration in tissue fluid

Question 10

which type of drug interaction is more predictable?

Answer 10

pharmacodynamic

Question 11

describe a pharmacokinetic drug interaction

Answer 11

drug A modifies the concentration of drug B that reaches its site of action

Question 12

name a drug that can increase rate of emptying of the stomach

Answer 12

metoclopramide

Question 13

name a drug that can decrease the rate of emptying of the stomach

Answer 13

atropine

Question 14

how can antibiotics cause failure of contraception?

Answer 14

enterohepatic recirculation of oral contraceptives may be reduced by antibiotics

Question 15

what effect does phenytoin have on the efficacy of warfarin?

Answer 15

decreases by inducing enzymes

Question 16

what effect does cimetidine have on warfarin?

Answer 16

increases efficacy by inhibiting enzymes

Question 17

what is the result of the drug interaction between simvastatin and grapefruit juice?

Answer 17

myopathy

Question 18

what is the result of the drug interaction between warfarin and clarithromycin?

Answer 18

enhanced anticoagulation

Question 19

what is the result of the drug interaction between phenytoin and omeprazole?

Answer 19

phenytoin toxicity

Question 20

what is the result of the drug interaction between azathioprine and allopurinol?

Answer 20

azathioprine toxicity

Question 21

what is the result of the drug interaction between catacholamines and MOA inhibitors?

Answer 21

hypertensive crisis

Question 22

what is the result of the drug interaction between ciclosporin and st johns wort?

Answer 22

loss of immunosuppression

Question 23

what is the result of the drug interaction between lithium and diuretics?

Answer 23

lithium toxicity

Question 24

what is the result of the drug interaction between methotrexate and NSAIDs?

Answer 24

methotrexate toxicity

Question 25

what is the result of the drug interaction between salbutamol and atenalol?

Answer 25

inhibits the bronchodilator effect

Question 26

what is the result of the drug interaction between benzodiazepines and alcohol?

Answer 26

increased sedation + risk of falls

Question 27

what is the result of the drug interaction between ACEis and NSAIDs?

Answer 27

increased risk of renal impairment

Question 28

what is the result of the drug interaction between digoxin and diuretics?

Answer 28

digoxin toxicity

Question 29

what is the result of the drug interaction between warfarin and aspirin/NSAIDs?

Answer 29

increased risk of bleeding

Question 30

what effect do competitive inhibitors have on Km and Vmax?

Answer 30

high Km | same Vmax

Question 31

what effect do non competitive inhibitors have on Km and Vmax?

Answer 31

same Km | low Vmax

Question 32

what is the extraction ratio (ER) of a drug?

Answer 32

the rate of drug removal from the bloodstream relative to the rate of drug delivery to the liver

Question 33

what effect does reduced synthesis of plasma proteins due to liver disease have on drugs?

Answer 33

increased toxicity of highly protein bound drugs with low TRs i.e. phenytoin

Question 34

what effect does reduced synthesis of clotting factors due to liver disease have on drugs?

Answer 34

enhanced sensitivity to oral anti-coagulants

Question 35

what effects can drugs have on hepatic encephalopthy?

Answer 35

can be worsened or precipitated sedatives, opioids

Question 36

what effect can drugs have on ascites?

Answer 36

may be worsened by drugs that cause fluid retention such as NSAIDs