Pharmacology Chapter 6 - Drug-Drug and Drug-Food Interactions.

Question 1

Intensification of effects (Potentiative.)

Answer 1

one drug may intensify the effect of another by increasing therapeutic (beneficial) or adverse (harmful) effects.

Question 2

Examples of intensification

Answer 2

Beneficial - when ampicillin is given with sulbactum, ampicillin’s effects are intensified.

Harmful - warfarin is an anticoagulant. When taken with aspirin, the risk of spontaneous bleeding is increased.

Question 3

Reduction of effects (inhibitory) (def)

Answer 3

reduced therapeutic effect or reduced adverse effect.

Question 4

Examples of reduction.

Answer 4

Reduced therapeutic - propanol and terbutaline (bronchial dilator) propanol reduces effects or terbutaline.

Reduced adverse - excessive morphine is bad, so when given with naloxone - the toxic side effects are reduced.

Question 5

Four mechanisms of drug-drug interactions….

Answer 5

1. Direct chemical or physical
2. Pharmacokinetic
3. Pharmacodynamic.
4. Combined toxicity.

Question 6

Direct Chemical or physical - (think what it does in IV…)

Answer 6

Most occur when drugs are in IV solution. Precipitate - BAD BAD BAD BAD BAD. So don’t combine drugs in IV.

Question 7

Pharmacokinetic Interactions (4 types.)

Answer 7

Altered absorption, altered distribution, altered metabolism, altered renal excretion.

Question 8

Altered Absorption -

Answer 8

drug interactions affect absorption. Example - elevation of gastric pH by antacids prevent proper absorption of drugs from stomach.

Question 9

Altered Distribution

Answer 9

Competition for protein binding (binding to plasma albumin, alteration of plasma pH.)

Question 10

Altered Metabolism

Answer 10

Some drugs decrease or increase others’ metabolism - catabolism by P450.

Question 11

Altered Renal Excretion

Answer 11

Alteration of filtration, re absorption and secretion.

Question 12

Pharmacodynamic Interactions

Answer 12

Interactions at the same receptor (antag/agon)….also, if even 3 different drugs have different mechanisms of action and act through different sites, if they both influence simmer physiological responses, these could be potentiative or inhibitory.

Question 13

Combined Toxicity

Answer 13

combined toxic effects of both drugs could be harmful. (More drug, more poison.)

Question 14

What is the clinical significance of Drug-Drug interactions?

Answer 14

Rise of serious drug interactions is directly proportional to the number of drugs an individual is taking.

Question 15

How to minimize drug-drug interactions?

Answer 15

Reduce number of drugs being taken, take thorough drug history, and monitor early signs of toxicity.

Question 16

Drug-Food interactions and alteration of rate of absorption.

Answer 16

Food decreases rate and extent of drug absorption. High fiber foods can reduce absorption (like digoxin for heart.)

Increase - high calorie food more than doubles the absorption of saquinavir (a drug for HIV.)

Question 17

Impact of Food on Drug Metabolism (Grapefruit)

Answer 17

grapefruit juice may inhibit metabolism of certain drugs. May inhibit cytochrome P450 enzymes

Question 18

Impact of Food on Drug Toxicity (MAO inhibitor example)

Answer 18

Increased toxicity - mao inhibitors - antidepressants - react with foods containing tyramine (aged cheeses, etc.) and increase blood pressure to dangerous levels.

Question 19

Impact of Food on Drug Toxicity (decrease) (think Vitamin K)

Answer 19

Foods rich with vitamin K can reduce the effects of warfarin. - creates clotting.

Question 20

Timing of drug administration and meals -

Answer 20

may increase/decrease absorption, cause upset stomach, etc.