drug interactions

Question 1

when does a drug interaction occur?

Answer 1

occurs when a substance alters the expected performance of a drug

Question 2

what are the two types of drug interactions?

Answer 2

1. Pharmacodynamic
2. Pharmacokinetic

Question 3

when do pharmodynamic interactions occur?

Answer 3

Occur when drugs have an effect on the same target or physiological system

Question 4

when do pharm-kinetic reactions occur?

Answer 4

Occur when a drug affects the pharmacokinetics (absorption, distribution, metabolism or excretion) of another drug

Question 5

describe pharmacodynamic interactions

Answer 5

Pharmacodynamic interactions are either synergistic or antagonistic
Due to drugs acting on the same drug receptor(s) or physiological system
Generally predictable (related to pharmacology of drug)
Highly selective drugs are less likely to be problematic

Question 6

Pharmacodynamic interactions (drug receptors)
Synergistic interaction

Question 7

Pharmacodynamic interactions (drug receptors)
Antagonistic interaction

Question 8

Pharmacodynamic drug reactions (physiological system)
Synergistic interaction

Question 9

Pharmacodynamic drug reactions (physiological system)
Synergistic interaction

Question 10

Pharmacodynamic drug reactions (physiological system)
Synergistic interaction

Question 11

define synergy

Answer 11

interaction of drugs such that the total effect is greater than the sum of the individual effects (1+1>2)

Question 12

define antagonism

Answer 12

an antagonist is a substance that acts against and blocks an action (2 drugs opposed to each other) (1+1=0)

Question 13

define summation

Answer 13

different drugs used together to have the same effect as a single drug would (1+1=1)

Question 14

define potentiation

Answer 14

enhancement of one drug by another so that the combined effect is greater than the sum of each one alone (1+1=1+1.5)

Question 15

define pharmacodynamics

Answer 15

the effect the drug has on the human body

Question 16

define pharmacokinetics

Answer 16

what the body does with the drug (the disposition of a compound within an organism)

Question 17

risk factors f

Answer 17

Narrow therapeutic index
Steep dose/response curve
Saturable metabolism

Question 18

what are the pharmacokinetics mechanisms?

Answer 18

Absorption, Distribution, Metabolism, Excretion

Question 19

describe Absorption in ADME

Answer 19

Motility – if the gut has slowed digestion, the drugs won’t work as well (oral contraceptive pill and antibiotics is the most common interaction)
Acidity – pH and pKa interactions.
Solubility
Complex formation

Question 20

Describe distribution in ADME

Answer 20

Drugs can go into the proteins, other tissues or the effect site
Protein binding

Question 21

How is protein binding helpful in drug distribution?

Answer 21

If you give 2 highly protein bound drugs, they will make each other strong and increase their effect so you always make sure you know what drugs the patient has taken before giving them new drugs

Question 22

describe metabolism in ADME

Answer 22

CYP450
INHIBITION
INDUCTION
EXCRETION

Question 23

describe CYP450 in metabolism

Answer 23

Haemoproteins
Metabolise many substrates – endogenous and exogenous

Question 24

describe inhibition in metabolism

Answer 24

Drug A blocks metabolism of drug B, leaving more free drug B in the plasma so it has an increased effect

Question 25

describe induction in metabolism

Answer 25

Drug C induced CYP450 isoenzyme leading to increased metabolism of drug D so it has a decreased effect

Question 26

two types of excretion in metabolism

Answer 26

renal
billary - minor

Question 27

describe renal exertion in metabolism

Answer 27

pH dependant
Weak bases – cleared faster if urine acidic
Weak acids – cleared faster if urine alkali

Question 28

what are the different types of pharmacodynamic mechanisms

Answer 28

receptor based
signal transduction
physiological systems

Question 29

describe receptor based pharmacodynamic mechanisms

Answer 29

Agonists
Partial agonists
Antagonists
Competitive
Non-competitive

Question 30

describe physiological systems in pharmacodynamic mechanisms

Answer 30

Different drugs that effect different receptors, but in the same physiological system

Question 31

two drugs to be aware of

Answer 31

Warfarin – lots of interactions – enzyme induction
Acute kidney injury – NSAIDs, ACEi