Drug-Drug Interactions

Front 1

What are the ways drugs can be combined to increase the effect?

Back 1

Additive, synergistic and potentiation

Front 2

Additive

Back 2

Means the effect of the drug is equal to their sum, basically the effect they each have on their own put together

Alcohol and diphenhydramine

Front 3

Synergistic

Back 3

The effect is greater than what you would expect the sum to be (for example you would expect the sum of X + X to be 2X but you get 3X because they reinforce one another)

Phenobarbital and alcohol

Front 4

Potentiation

Back 4

Is where the effect of a drug is increased by another substance that has no effect

Penicillin and clavulinic acid (cleaves an enzyme that improves penicillins action, no effect otherwise)

Front 5

What are the three form of antagonism

Back 5

Functional, dispositional and receptor

Front 6

Functional antagonism

Back 6

Like physiological where a drug acts oppositely on the system

Front 7

Dispositional antagonism

Back 7

Effects where the drug goes in the body and therefore could substantially alter the function

Front 8

Receptor antagonism

Back 8

An agent with low efficacy competes with another for the binding site

Front 9

Pharmaceutical

Back 9

Is an interaction that occurs prior to drug administration

Ketamine and Midazolam: form crystals in solution

Front 10

Site of action (receptor)

Back 10

morphine and naloxone compete for the same drug binding site (naloxone has high affinity but low efficacy and therefore is a competitive antagonist)

Front 11

Site of action (physiological)

Back 11

Furosemide (loss of K+) and digitalis (activity increases with gain of potassium)

- Synergistic but can increase likelihood of side effects

Viagra and alpha antagonist (both cause vasodilation = hypotension)

- Additive (they both have similar effect, but one doesn't cause the other to work more)

Front 12

Common drug absorption interactions

Back 12

Changes in pH

Chelation and adsorption

Changes in gastric emptying/motility

transporter interactions

intestinal blood flow

Front 13

Changes in pH

Back 13

antacids alter the pH and will affect the absorbability of the drug based off of pKa

Front 14

Changes in intestinal blood flow

Back 14

Vasoactive molecules that affect blood flow, can effect how quickly or slowly a drug reaches its target

Front 15

transporters

Back 15

SLCs are more implicated in absorption

Valproate and verapamil compete for SLC mediated absorption

Front 16

Chelation

Back 16

Tetracycline can bind iron that makes an insoluble complex (therefore reduces its absorption)

Front 17

Adsorption

Back 17

Cholestyramine binds to tetracycline and lower absorbability

Front 18

How does plasma protein binding effect distribution?

Back 18

Two drugs that bind plasma proteins can compete with one another where one drug is generally displaced leading to increased absorption

Front 19

What is an example of protein binding competition?

Back 19

Warfarin and sulfonamide

Front 20

Why is Vd relevant to plasma protein binding?

Back 20

A low Vd indicates that a greater portion of the drug is protein bound

Front 21

How does plasma protein binding competition pertain to therapeutic index?

Back 21

If a drug has a low therapeutic index and is outcompeted for plasma protein binding the free drug concentration increases meaning there is greater potential for toxic side effects

Front 22

What are the major drug-drug interactions in regard to metabolism?

Back 22

Induction of inhibition of CYPs

Front 23

What are examples of somethings that induce CYP3A4

Back 23

Rifampicin and St. John's Wort (herbal)

Front 24

Sulforaphane

Back 24

Induces Phase II enzymes

Front 25

Grapefruit Juice

Back 25

Inhibits CYP3A4

Front 26

Itraconazole

Back 26

Inhibits CYP3A4

Front 27

Why are drugs that go through first pass metabolism more greatly affected by CYP modulators?

Back 27

Because the drug is metabolized prior to entering the systemic circulation and therefore this can greatly alter the systemic concentration of the drug

Front 28

How does plasma protein binding influence excretion?

Back 28

Same as with the distribution, where a drug can outcompete another for plasma protein binding resulting the displaced drug to be more readily excreted

Front 29

Amiodarone and digoxin

Back 29

Amiodarone inhibits P-gp which results in plasma accumulation of digoxin

Front 30

How can tubular reabsorption be altered?

Back 30

drugs that manipulate urine pH in order to control ionization of other drugs and reduce their reabsorption