#8 Drug Interactions 9/17/15

Question 1

___% of all americans take at least one prescription drug.

Answer 1

70%
50% take at least 2
20% take 5 or more!

Question 2

What is a synergistic effect?

Answer 2

When a drug’s effect is increased (Can be by interaction with another drug) *the combined activity of two drugs produce an effect greater than the maximum effect produced by either drug alone.

Question 3

What is an antagonistic effect?

Answer 3

When a Drug’s effect is decreased (Possibly by another drug.

Question 4

What are the possible consequences of drug interactions?

Answer 4

• Synergistic effect
• Antagonist effect
• New effect produced
• Unexpected drug effect

Question 5

What are some examples of Antagonistic Drug interactions?

Answer 5

• Altering drug metabolism: One drug stimulates metabolism of another
• Drugs compete at same receptor
• Drugs create opposing actions through signaling at different receptors.

Question 6

What is potentiation?

Answer 6

A second drug with a different activity enhances the activity of the first drug.

Question 7

How does potentiation take place?

Answer 7

Drug B enhances absorption, alters distribution or inhibits elimination of Drug A

Question 8

_____ inhibits bacterial cell wall synthesis.

Answer 8

Penicillin

Question 9

_____ inhibits bacterial protein synthesis.

Answer 9

Tetracycline

Question 10

What happens if an individual were treated eight both penicillin and tetracycline?

Answer 10

An antagonistic effect
Penicillin inhibits new cell wall, so bacteria must be actively diving for this to occur. Tetracycline stops protein synthesis of bacteria so it attenuates the effect of penicillin.

Question 11

______ chelates divalent ions.

Answer 11

Tetracycline

Question 12

What does Chelation do?

Answer 12

Interferes with absorption and antimicrobial activity.

Question 13

Taking antacid can diminish the effectiveness of _______.

Answer 13

Tetracycline

Question 14

What is an example of potentiation?

Answer 14

Neostigmine potentiates the activity of Succinylcholine:

1. Succinylcholine acts at nicotinic acetylcholine receptor to produce neuromuscular block.
2. Succinylcholine is hydrolyzed by pseudocholinesterase
3. Inhibition of pseudocholinesterase by neostigmine will increase the plasma T1/2 of succinylcholine.

Question 15

What are some examples of unexpected drug effects?

Answer 15

Metabolism of ethanol

ethanol (via alcohol dehydrogenase) is turned to acetaldehyde, which if accumulated can yield serious headaches.

Question 16

What is Disulfiram?

Answer 16

An inhibitor of aldehyde dehydrogenase thus producing undesirable side effects if taken with alcohol due to the accumulation of acetaldehyde. *Used to treat alcholics

Question 17

What is Summation?

Answer 17

The combined activités of two drugs acting at the same or similar sites

Question 18

What are the 3 types of summation?

Answer 18

Additive = drug action is interchangeable when doses at fractions of their EC50.

Infra-additive = yields less than additive response when dosed as above)

Supra-additive = Yield more than the additive response when dosed as above.

Question 19

What is an example of Summation acting at different sites?

Answer 19

General anesthetics midazolam (potentiates GABA receptor mediated hyper polarization) and sevoflurane (Inhalation anesthetic)

Question 20

What is an example of Summation acting at the same site?

Answer 20

Opioids morphine and meperidine

Question 21

What are some examples of synergism?

Answer 21

CCl4 (carbon tetrachloride) is hepatic-toxic and the toxicity is substantially enhanced by ethyl alcohol.

HAART Therapy (Highly active anti-retrovirus treatment = treatment of AIDS using multiple drugs from different classes

Question 22

What are Pharmaceutical interactions?

Answer 22

Drug incompatibility of a physical or chemical nature.

Question 23

What would be an example of Pharmaceutical interaction?

Answer 23

Mix organic acid and an organic base and one or both precipitates.

Question 24

What are the 4 types of Pharmacokinetic interactions?

Answer 24

1. Absorption = interaction can affect the rate or extent of effective absorption of drug into circulation.
2. Distribution = After drug is absorbed, an interaction may alter it’s distribution or its rate of transfer from one site to another.
3. Metabolism = Most drugs metabolized in liver by microsomal P450 enzymes, so Inhibition of CYP enzymes responsible for many drug interactions.
4. Excretion

Question 25

What factors will affect the absorption of drugs?

Answer 25

pH of lumen fluids, enzyme activity and intestinal motility

Question 26

What is an example of an absorption reaction?

Answer 26

Chelation of tetracycline diminishes its absorption.

Question 27

What is an example of a distribution interaction?

Answer 27

Distribution across plasma membrane can be affected by drugs that:
1. Alter p-glycoprotein activity levels.
2. Alter pH gradients
3. Disrupt membrane barriers
EX. Drug A alters endothelial cell structure = disturbs blood brain barrier and drug B now penetrates the CNS.

Question 28

What are some examples of Metabolism interactions?

Answer 28

1. Erythromycin irreversibly inhibits CYP3A4 so it will affect any drug metabolized by CYP3A4.
2. Phenobarbital, pheytoin and carbamazepine all induce microsomal enzymes that will increase the metabolism of other drugs.

Question 29

_______ are more rapidly excreted in alkaline urine.

Answer 29

Weak acids (like aspirin)

Question 30

______ are more rapidly excreted in basic urine.

Answer 30

Weak bases (like amphetamine)

Question 31

Aspirin (weak acid) clearance is increased by administration of _______.

Answer 31

Na+HCO3- (sodium bicarbonate)

Question 32

Amphetamine (weak base) clearance is increased by administration of ______.

Answer 32

NH4+Cl- (Ammonium chloride)

Question 33

What is Renal transport inhibition?

Answer 33

Another method of drug interaction (excretion) where one drug inhibits the renal transport of another drug, thereby increasing the duration of the action of the drug.* Probenecid extends the duration of action of Penicillin.

Question 34

What are Pharmacodynamic interactions?

Answer 34

*Drug A blocks transmitter reptake,
Drug B stimulates transmitter release.

Interactions where Drug B will be less effective after drug A because transmitter stores get depleted.