W4: Pharmacokinetics mechanism of drug-drug interaction

Question 1

One of the drug-drug interaction at the absorption phase is the _____.

Answer 1

Changes in pH

Question 2

Some drugs are capable of changing the pH, disrupting the ____ of another drug

Answer 2

ionization

Question 3

Drug-drug can also form _____ in the GIT to form insoluble complex for absorption.

Answer 3

complexes

Question 4

Some drug affect intestinal ______. Higher_____, higher absorption rate.

Answer 4

blood flow

Question 5

Bacterial flora can affect drug absorption by either _______ of drugs by metabolism or _____ in active form to be reabsorbed to liver.

Answer 5

can either inactive drugs or conjugates into active form

Question 6

A type of drug that can be inactivated by bacterial flora is _______

Answer 6

Digoxin (medication for heart failure)

Question 7

A type of drug that can be activated by bacterial flora is _______

Answer 7

Oral hormone contraceptives

Question 8

Why is digoxin given with antibiotics? Is it safe?

Answer 8

Antibiotics kills the normal bacterial flora and this allows an increase in digoxin levels in the body.

Usually digoxin dose have to be reduced if given with antibiotics, otherwise it will lead to toxicity.

Question 9

How will antibiotics affect oral hormone contraceptive? Consequences include?

Answer 9

Antibiotics kills the normal bacterial flora and oral hormone contraceptive won’t be activated. No effect will happen.

It might lead to unintended pregnancy because hormone regulation is normal.

Question 10

How will drug-drug interaction be presented in distribution phase?

Answer 10

They will compete for plasma protein binding

Question 11

How can two drugs fight for plasma protein binding?

Answer 11

They both bind at different degree hence the one with lower affinity will be displaced by another drug.

Question 12

What are the two outcomes for drugs that fight for plasma protein binding?

Answer 12

The free drug (lower affinity for plasma protein) might cause:

1. Increase in therapeutic effect due to increase distribution
2. Toxicity if the free drug has a low therapeutic index

Question 13

How can drug-drug interaction affect metabolism?

Answer 13

Drug can bind to lipid membrane of endoplasmic reticulum, which induce the microsomal cytochrome P450 enzymes (CYP450).

This can lead to competitive inhibit or induce metabolism of another drug.

Question 14

What happens when drug A competitively induces metabolism of drug B?

Answer 14

It will lead to the increase in drug B metabolites and decrease the effect of drug.

Question 15

What happens when drug C competitively inhibit metabolism of drug B?

Answer 15

It will lead to excessive drug B levels and toxicity. Emergence of side effects.

Question 16

How can toxicity happen in competitively inducing metabolism?

Answer 16

A non toxic substance goes through metabolism to transform into its toxic metabolite.

Paracetamol’s metabolite , N-acetylbenzoqionone imine is toxic = paracetamol poisoning.

Question 17

There is an ______ tolerance of drugs when competitively induced to metabolize.

Answer 17

Increase tolerance of drugs because there are increased levels of inactive metabolites

Question 18

Factors affecting elimination of drug includes cardiac output, ________ and ________________.

Answer 18

• cardiac output
• lipid solubility
• glomerular filtration rate

Question 19

If a drug goes through active tubular secretion (elimination), how can another drug affect this?

Answer 19

The other drug can competitively bind to the protein responsible for active transport, reducing the excretion rate and increases the concentration of the object drug.

• can lead to toxicity lorh

Question 20

What is active tubular secretion?

Answer 20

When a drug relies on a protein transporter for elimination through the proximal tubules

Question 21

What is object drug?

Answer 21

Object drug is the drug administered for an intended therapeutic effect that can be modified by another drug through drug interaction

Question 22

What is precipitant drug?

Answer 22

The drug responsible for affecting the pharmacokinetics or pharmacodynamics of the object drug.

Question 23

What is passive tubular reabsorption and what is it affected by?

Answer 23

The reabsorption of drug in the tubules regulated by concentration and lipid solubility.

Question 24

which drug is easier to reabsorb? non-ionized or ionized drug ?

Answer 24

Non-ionized drugs are easier to be reabsorbed. In other words, ionized drugs are easier to be excreted .

Question 25

Lithium is a positively charged element used to treat bipolar and depression. How can sodium bicarbonate interact with lithium?

Hint: elimination

Answer 25

Sodium bicarbonate can cause the urine to be alkaline which increases the clearance of lithium. A consequence of this is a decrease in lithium action in the body.

Question 26

How can antacids affect the clearance of salicylates? Salicylate are salts of salicylic acid, use as analgesic agent for mild and moderate agents.

Answer 26

Antacids increases the pH of urine to increase clearance rate of salicylates and decrease its action.

Question 27

In acidic urine, weakly acidic drugs will ______ excreted.

Answer 27

will not be excreted because it is non-ionized.

Question 28

In acidic urine, weakly basic drugs will ______ excreted.

Answer 28

will be excreted because it is ionized.

Question 29

In alkaline urine, weakly basic drugs will ______ excreted.

Answer 29

will not be excreted because it is non-ionized

Question 30

In alkaline urine, weakly acidic drugs will ______ excreted.

Answer 30

will be excreted because it is ionized.