Pharmacokinetics

Question 1

What does ADME in p/kinetics stand for ?

Answer 1

Absorption
Distribution
Metabolism
Excretion

Question 2

Primary goal of pharmacokinetics?

Answer 2

To understand how drugs reach and maintain effective concentrations at their site of actions

Question 3

What is the most common mechanism of drug absorption

Answer 3

Passive diffusion

Question 4

What factors are likely to affect passive diffusion?

Answer 4

Molecular size
Lipid solubility
pKa of drug
pH of environment

Question 5

What is the significance of drugs pKa?

Answer 5

It is the pH at which the drug is 50% ionized and 50% non ionized

Question 6

Which form of drug rapidly enters cell membrane?

Answer 6

Nonionized ( lipid-soluble ) form

Question 7

What equation helps predict drug ionization across membranes

Answer 7

Henderson-hasselbach

Question 8

Where are weak based best absorbed?

Answer 8

Small intestines (higher pH)

Question 9

What is the role of active transport in absorption?

Answer 9

Moves drugs against concentration gradient using energy ie 5-FU uses uracil transporter

Question 10

What is the main disadvantage of oral drug administration in ruminants?

Answer 10

Rumen microbes may inactivate the drug

Question 11

What is the 1st pass effect ?

Answer 11

Metabolism of a drug in gut or liver before it reaches systemic circulation

Question 12

Which route bypass the 1st pass effect partially in dogs?

Answer 12

Rectal route (via rectal veins to caudal vena cava)

Question 13

Which route provides the fastest onset ?

Answer 13

Intravenous

Question 14

What is the main advantage of inhalation

Answer 14

Rapid onset and reversibility ie isoflurane

Question 15

Why might IM affect meat quality in food animals ?

Answer 15

May cause discoloration/ abscesses, reducing carcass value

Question 16

What are main Barriers to drug distribution in CNS

Answer 16

Active transporters ie P-glycoproteins
Glial cells and tight junctions in epithelial cells
Blood brain barrier
CSF fluid

Question 17

What protein bind to acidic drugs vs basic drugs

Answer 17

Acidic -albumin
Basic -alpha 1 acid glycoprotein
Steroid hormone and thyroid -specific globulins

Question 18

What is the main organ for metabolism

Answer 18

Liver

Question 19

What is purpose of phase 1

Answer 19

Introduce/unmask functional groups
Via oxidation, reduction, hydrolysis

Question 20

Which enzymes and give location of phase 1 oxidation

Answer 20

CYP450
Location -smooth endoplasmic reticulum

Question 21

What conjugation pathway is deficient in cats?

Answer 21

Glucuronidation

Question 22

What is goal of phase 2 metabolism

Answer 22

Conjugate drugs to make them more water soluble and excretable

Question 23

What conjugation is absent in dogs ?

Answer 23

Acetylation

Question 24

What is enterohepatic recycling?

Answer 24

Reabsorption of drugs from gut after bile excretion , prolonging drug action

Question 25

What is primary route of drug excretion?

Answer 25

Renal

Question 26

What 3 processes govern renal drug excretions

Answer 26

Glomerular filtration Active tubular transport Passive tubular transport

Question 27

What enhances excretion of weak acids / bases?

Answer 27

Altering ph to increase ionization

Question 28

What is the role of biliary excretion ?

Answer 28

Excretes parent drug /conjugated into bile May lead to enterohepatic recirculation

Question 29

Gives examples of oxidation with drug examples

Answer 29

1.side chain and aromatic hydroxylation-propranolol 2. O-dealkylation-morphine 3.N-oxidation-nicotine 4.S-oxidation-phenothiazines 5.Deamination-lidocaine 6.Desulfuration-thiopental

Question 30

Give examples of drugs undergo reduction

Answer 30

Chloramphenicol and Naloxone

Question 31

Give 2 types of hydrolysis processes and examples of drugs undergoing the process

Answer 31

1.Esterases occur in nonmicrosomal systems-acetylcholine found in liver , plasma and other tissues 2.amidases-non microsomomal found in liver ie acetozolamide

Question 32

Examples of drugs undergoing phase 2 metabolism

Answer 32

1. Glucuronidation-aspirin, morphine, steroids 2. Glycine-salicylic acid 3. Glutathione-ethacrynic acid 4. Acetylation- sulfonamides 5.methylation-catecholamines 6.sulfate formation - catecholamines