3: Basic Pharmacology Definitions and Principles

Question 1

effects caused by a combination of toe or more drugs or when the effects of one drug are changed by the presence of other substances is called a

Answer 1

drug interaction

Question 2

in addition to drugs, drug interactions can be caused by:

Answer 2

• another drug
• metabolic enzyme
• herbal medicine
• food
• drink
• environmental chemical agent

Question 3

“when a combination of two or more drugs impedes or inhibits one or more of the drugs being taken/administered” is called

Answer 3

altered absorption

Question 4

in chelation, what substances bind?

Answer 4

aluminum, magnesium, calcium, iron-containing medications can irreversibly bind to some antibiotics like doxycycline or oral fluoroquinolones which reduces the amount of drug absorbed

Question 5

what is the definition of chelation?

Answer 5

complex formation involving a metal ion and two or more polar groupings of a single molecule

Question 6

“response elicited by combined drugs is equal to the combined responses of the individual drugs” or 1+1=2

Answer 6

additive effects

Question 7

an example of drugs that could give an additive effect?

Answer 7

• drugs with CNS depressant effects

- alcohol and medications for insomnia and sedating antihistamines

Question 8

“response elicited by combined drugs is greater than the combined responses of the individual drugs” or 1+1=3

Answer 8

synergism

Question 9

example of drugs causing synergism

Answer 9

vancomycin and gentamicin to treat bacterial endocarditis

Question 10

describe how synergism result works

Answer 10

combination of these medications is more effective in killing the bacteria causing the infection than the effect that would be achieved by using either of the antibiotics alone

Question 11

what is it when “one drug inhibits the effect of another drug and the antagonist usually has no inherent activity” or 1 + 1=0

Answer 11

antagonism

Question 12

example of antagonism

Answer 12

naloxone (an opioid narcotic antagonist) is administered in opioid narcotic overdose situations

Question 13

“when a drug which has no principal effect enhances the effect of a second drug” or when 0+1=2

Answer 13

potentiation

Question 14

example of potentiation

Answer 14

amoxicillin with clavulanate = augmentin

Question 15

explain how augmentin is an example of potentiation

Answer 15

amoxicillin is a penicillin antibiotic which inhibits bacterial wall synthesis and clavulanate has no killing action or principle effect on its own but it protects the amox. molecule by binding to beta-lactamases produced by bacteria that inactivate amox.

Question 16

example of altered metabolism

Answer 16

interactions can occur when cytochrome P-450 metabolic enzymes are induced or inhibited by a drug

Question 17

where is cytochrome P-450 located and what does it catalyze?

Answer 17

located in liver endoplasmic reticulum and is a microsomal superfamily of isoenzymes that catalyzes the oxidation of many drugs

Question 18

enzyme INDUCTION would :

Answer 18

• increase the rate of drug metabolism and conversion to inactive metabolite
• lower systemic drug levels

Question 19

enzyme INHIBITION would :

Answer 19

• decrease rate of drug metabolism and conversion to an inactive metabolite
• higher systemic drug levels

Question 20

how can altered hepatic blood flow affect altered metabolism ?

Answer 20

• if hepatic blood flow diminished
• drug contained in systemic circulation not delivered to metabolic enzymes in liver
• could reduce drug metabolism

Question 21

how can the liver alter metabolism?

Answer 21

impaired liver function could also reduce drug metabolism (impaired liver function could be secondary to liver disease, hepatitis, or drug toxicity, like alcohol abuse or amiodarone)

Question 22

in general, enhancing renal blood flow will:

Answer 22

• increase glomerular filtration rate (GFR)

- increase filtration or elimination of the drug (at the glomerulus for drugs eliminated via the kidneys)

Question 23

in general, reducing renal blood flow will:

Answer 23

• decrease glomerular filtration rate (GFR)

- decreased filtration or elimination of drug (at the glomerulus for drugs eliminated via the kidneys)

Question 24

why are we especially worried about kidney function in elderly patients?

Answer 24

because GFR decreases with age

Question 25

removal of drugs from the body occurs via multiple routes, but what is most important?

Answer 25

through the kidneys into the urine

Question 26

elimination of drugs via the kidneys into urine involved which 3 processes

Answer 26

- glomerular filration (GFR) - active proximal tubular secretion - passive distal tubular resorption

Question 27

4 ways of drug elimination by the kidney

Answer 27

1. filtered at the renal glomerulus 2. secreted into the proximal tube 3. reabsorbed from the tubular lumen and transported back into the blood 4. excreted in the urine

Question 28

what possible factors affect GFR and drug elimination and how?

Answer 28

any factors which decrease GFR could lead to: - decrease in drug excretion - increase in drug accumulation - increase in plasma concentration - adverse effects

Question 29

what is the cause and result of drug induced renal impairment (renal toxicity)?

Answer 29

impaired renal function could be secondary to renal disease or drug induced (non-steroidal anti-inflammatory drugs)

Question 30

common breakpoints for calculated creatinine clearance rates (CrCl) which require dosage adjustments are:

Answer 30

< 30-50 ml/min

Question 31

what effect does decreasing plasma protein binding have on kidneys?

Answer 31

could lead to increased free drug and increased filtration of drug at the glomerulus

Question 32

how can drugs interact with the proximal tube and how could this be blocked?

Answer 32

drugs may be secreted into the proximal tube for elimination via the urine and this process could be blocked (example: probenecid and penicillin together inhibits active tubular secretion of penicillin

Question 33

explain how competition for serum protein binding/ binding sites works

Answer 33

-a drug may be bound to albumin or other plasma proteins while in the systemic circulation (vascular space) & now contains a plasma concentration of both drug that is bound & drug that is unbound, may increase concentration of free, unbound drug "A"

Question 34

in competition for serum protein binding/ binding sites, what can occur in drugs that are highly protein bound?

Answer 34

if serum albumin levels are significantly decreased, the amount of free drug will be increased

Question 35

in competition for serum protein binding, what is the free drug available to do?

Answer 35

to bind to target receptors or may be metabolized and/or excreted

Question 36

in competition for serum protein binding, what type of equilibrium is established?

Answer 36

free drug in the systemic circulation is in equilibrium with tissue reservoirs, plasma proteins, and the target site

Question 37

in competition for serum protein binding, what does the "target site" usually consist of?

Answer 37

receptors and only the fraction of the drug that binds to specific receptors will have a pharmacologic effect

Question 38

explain the serum protein binding of a drug that is bound to albumin (or other plasma proteins)

Answer 38

cannot diffuse from the vascular space into tissues

Question 39

explain the serum protein binding of a drug that is less bound to albumin (or other plasma proteins)

Answer 39

can more readily diffuse from the vascular space into tissues

Question 40

explain the serum protein binding of a drugs that do not exhibit high levels of binding to plasma proteins

Answer 40

readily diffuse into tissues

Question 41

explain the results of serum protein binding of a drug that has high levels of binding to plasma proteins and readily diffuses into tissues

Answer 41

high level of binding to the site of pharmacologic action (receptors) and a high rate of elimination

Question 42

drugs that do exhibit high levels of binding to plasma proteins diffuse:

Answer 42

do NOT diffuse into the tissues as readily

Question 43

what is unique about drugs that do exhibit high levels of binding to plasma proteins and do not diffuse into tissues as readily

Answer 43

requires higher total plasma drug concentration to ensure adequate concentration of free drug (unbound) to reach the tissues or site of pharmacologic action

Question 44

what are some other important factors (other than plasma protein binding) that affect pharmacokinetics of a particular drug

Answer 44

drug molecule size, lipophilicity, rate of metabolism