Pharm: Drug-Drug Interactions

Question 1

Describe the concept of additive effects.

Answer 1

The effect of 2 drugs given together is equal to the sum of the responses to the same doses given separately.

Question 2

Describe the concept of antagonism.

Answer 2

The effect of 2 drugs given together is less than the sum of the responses to the same doses given separately.

Question 3

Describe the concept of pharmacodynamic interaction.

Answer 3

A change in the pharmacodynamics (what the body does to the drug i.e. absorp., met., elimination) of 1 drug caused by the interacting drug.

Question 4

Describe the concept of pharmacokinetic interaction.

Answer 4

A change in the pharmacokinetics (what the drug does to the body) of 1 drug caused by the interacting drug.

Question 5

Describe the concept of synergism.

Answer 5

The effect of 2 drugs given together is greater than the sum of the 2 responses when they are given separately.

Question 6

If EtOH is taken with CNS depressants, what happens?

Answer 6

More CNS depression

Question 7

If EtOH is taken with Acetaminophen, what happens?

Answer 7

Increased formation of hepatotoxic metabolites of acetaminophen.

Question 8

Antacids do what to gut absorption of some drugs?

Answer 8

Decreased gut absorption.

Question 9

Antihistamines (H1 blockers) have what effect on the nervous system (NS) when given with sedatives?

Answer 9

Additive effects with the drugs affected. (more NS depression)

Question 10

Antimuscarinic drugs have what effect on drugs absorbed from the small intestine?

Answer 10

Antimuscarinics will delay stomach emptying, delaying onset of drug actions b/c takes longer to get them to the SI for absorption.

Question 11

Barbiturates, especially phenobarbital can have what effect on the enzymatic clearance of some drugs metabolized by the liver?

Answer 11

Increased clearance due to enzymatic induction, possibly leading to decreases in drug effectiveness.

Question 12

Beta blockers can have what effect when taken concurrently with insulin?

Answer 12

Mask effects of hypoglycemia

Question 13

Beta blockers can have what effect when taken concurrently with Prazosin (HT med)?

Answer 13

Increased first dose syncope

Question 14

Bile acid-binding resins can have what effect on the absorption of acetaminophen, digitalis, thiazides and thyroxine?

Answer 14

Reduced absorption of the affected drug (bile acids needed for drug uptake- when bound, no absorption)

Question 15

Carbamazepine has what effect on several drugs’ pharmacokinetics because of its effect on pharmacodynamics?

Answer 15

Reduced effect of other drugs because of induction of metabolism.

Question 16

Cimetidine (treats GERD, H2 blocker) does what to metabolism of several drugs?

Answer 16

Inhibits metabolism, increases risk of toxicity

Question 17

Disulfiram has this effect when taken concurrently when consuming EtOH that actually makes it a treatment:

Answer 17

Creates an unpleasant reaction when drinking alcohol, which reduces the desire to drink. Inhibits aldehyde dehydrogenase, increasing hangover effect.

Question 18

Metronidazole and certain cephalosporins have this effect when taken concurrently with EtOH:

Answer 18

Inhibits aldehyde dehydrogenase, increasing hangover effect.

Question 19

Erythromycin does what to metabolism of several drugs?

Answer 19

Risk of toxicity due to inhibition of metabolism

Question 20

Grapefruit juice (furanocoumarins) has what effect on the absorption and metabolism of several drugs?

Answer 20

Increased absorption and decreased metabolism. Risk of toxicity due to inhibition of metabolism

Question 21

Ketoconazole and other azoles increase or decrease metabolism of several drugs?

Answer 21

Decrease metabolism. Risk of toxicity due to inhibition of metabolism

Question 22

Monoamine oxidase inhibitors (MOAs breakdown serotonin, melatonin, epi, norepi) have what effect on catecholamine releasers?

Answer 22

Increased norepinephrine in sympathetic nerve endings released by the interacting drugs.

Question 23

Monoamine oxidase (MOA) inhibitors have what effect when taken with tyramine-rich foods (fermented/pickled) and bevarages (fermented)?

Answer 23

Hypertensive crisis

Question 24

NSAIDs have what effect when taken with anticoagulants?

Answer 24

Increased bleeding tendency because of reduced platelet aggregation.

Question 25

NSAIDs have what effect when taken with ACE inhibitors, loop diuretics and thiazides?

Answer 25

Decreased antihypertensive efficacy of ACE inhibitor.

Reduced diuretic efficacy.

Question 26

Phenytoin is known to induce or inhibit metabolism of several drugs?

Answer 26

Induction of metabolism, reduced drug effects.

Question 27

Rifampin does what to the metabolism of several drugs?

Answer 27

Induction of metabolism, reduced drug effect.

Question 28

Ritonavir reduces or induces metabolism of several drugs?

Answer 28

Inhibition of metabolism, risk of toxicity

Question 29

SSRIs have what effect when taken concurrently with MOA inhibitors, tricyclic antidepressants, and St. John’s wort (antidepressant, anti-inflammatory)

Answer 29

Serotonin syndrome (hypertension, tachycardia, muscle rigidity, hyperthermia, seizures)

Question 30

Thiazides (diuretics) have what effect on plasma levels of lithium?

Answer 30

Increased plasma levels of lithium due to decreased total body water.

Question 31

Describe 3 ways that drugs can affect renal excretion of drugs.

Answer 31

1- Drugs reducing renal blood flow.
2- Drugs inhibiting specific renal transport mechanisms.
3- Drugs that alter uninary pH can alter the ionization state of drugs that are weak acids or weak bases leading to changes in renal tubular reabsorption.

Question 32

_______ is said to occur when a drug’s effect is increased by another agent that has no such effect.

Answer 32

Potentiation

Question 33

Give an example of potentiation.

Answer 33

Beta-lactamase inhibitors given with beta-lactamase susceptible penicillins.

Question 34

Regarding drug absorption:

What is an advantage to taking a drug with a meal?

Answer 34

Protection against gastric irritation by the drug

Question 35

Regarding drug absorption:

What would you expect to happen if you took a highly lipophilic drug with a meal high in fat?

Answer 35

It would take longer for the drug’s effects to begin because fatty foods stay in the stomach longer and would cause the drug to be retained in the stomach and delay its absorption in the lower GI tract.

Question 36

Antacids would have what effect on gastric absorption of acidic drugs?

Answer 36

More neutral gastric pH may slow absorption of acidic drugs

Question 37

What happens if a pt chews a drug that has an enteric coating?

Answer 37

The enteric coating will be rendered useless and the drug will be broken down in the stomach and less of the active drug will be available for absorption in the lower GI tract.

Question 38

How could you administer a bile-acid binding resin and drugs requiring bile-acids for absorption and have them not negatively impact one another?

Answer 38

Give them hrs apart, allowing one drug to do its job and then the other, once the one has been absorbed.

Question 39

What negative impact can some multivitamins have on other drugs given concurrently?

Answer 39

Some multivitamins bind drugs, making them unavailable for their pharmacokinetic intended purpose.

Question 40

You would expect to see greater drug activity of high percentage bound drugs in neonates and geriatric pts. Why?

Answer 40

Drugs that are 99% bound to serum proteins can experience a 3-4 fold increase in bioavailability when given to neonates and the elderly who have lower serum protein concentrations than pts of non-extreme age.

Question 41

Reducing blood flow to a site of local anesthetic administration with epinephrine, such as to repair a lac, serves two functions. Describe them.

Answer 41

Epinephrine reduces perfusion to the site of injection. This both reduces bleeding at the site, and also reduces uptake of the administered anesthetic into general circulation.

Question 42

You worry about lithium toxicity in pts with decreased:

Answer 42

total body water

Question 43

Which occurs more quickly and why: CYP induction or CYP inhibition?

Answer 43

CYP inhibition occurs more rapidly because induction entails initiating transcription, translation, etc of an enzyme, which takes time.

Question 44

Most drugs have a wide or narrow therapeutic index?

Answer 44

Wide

Question 45

Briefly describe the process of enterohepatic recirculation.

Answer 45

Drugs (such as morphine) are metabolized in the liver, excreted with bile acids into the GI tract, and then reabsorbed in the lower GI tract and re-metabolized and re-excreted, but not until after having more effects on the body following 2nd absorption.