Drug Metabolism and Transport

Question 1

drug metabolism

Answer 1

chemical alteration of a drug which allows it to be more easily excreted

Question 2

what happens when a drug is taken orally

Answer 2

• goes into the GI tract where it can encounter enzymes in the intestine and then is absorbed and sent to the liver where is encounters more enzymes
• in the GI tract or in the liver, it can experience presystemic extraction

Question 3

where are the cellular metabolic enzymes located?

Answer 3

• smooth endoplasmic reticulum
• cytosol
• mitochondria
• lysozymes

Question 4

most common microsomal enzymes

Answer 4

• cytochrome P450

- UDP glucoronosyltransferase

Question 5

phase 1 metabolism

Answer 5

• oxidation

- via CYP 450q

Question 6

phase 2 metabolism

Answer 6

• conjugation

- glucuronidation

Question 7

classifying cytochromes

Answer 7

• first number is the family
• letter is the subfamily
• second letter is the isoform

Question 8

racemic mixtures of drugs

Answer 8

• one is often more active

- enantiomers can be substrates of different enzymes

Question 9

what are the different ways a metabolite can interact with the body

Answer 9

• inactive
• active
• toxic/reactive

Question 10

prodrug

Answer 10

-when the drug itself is not active and the metabolite is the active form

Question 11

multiple routes of metabolism

Answer 11

• this could have toxic implications if the primary route is saturated and the secondary route produces a toxic metabolite
• this is the case with acetaminophine

Question 12

acetaminophen toxicity is increased by

Answer 12

• anything that increases bioactivation (increases the specific CYP enzyme activity)
• anything that empairs detoxification
• anything that depletes glutahtione levels

Question 13

inhibitors and inducers of drug metabolism

Answer 13

• inhibitors decrease enzyme activity giving less metabolite
• inducers increase enzyme activity and produce more metabolite
• this has opposite effects depending on if the drug is a prodrug or not
• not a big problem when the therapeutic window spans the change in drug concentration but when it doesn’t, it could be a problem

Question 14

pharmacoenhancement

Answer 14

• this is when you add another drug to the treatment in order to enhance the effect of the first drug
• usually inducers or inhibitors of the metabolizing enzyme of the first drug