DDIs

Question 1

When drug interactions take place when they are mixed in syringes, vials, or fluids prior to the administration of the drug to an animal, that is an in vitro/vivo (choose) drug-drug interaction.

Answer 1

(In vitro)

Question 2

What type of interaction is one that occurs between active ingredients, inactive ingredients, vehicles, and/or preservatives?

Answer 2

(Pharmaceutical interaction)

Question 3

IV fluoroquinolones should not be mixed with anion/cation (choose) containing fluids/solutions to prevent chelation and precipitate formation.

Answer 3

(Cation)

Question 4

What will be formed by the mixture of sodium bicarbonate with a calcium-containing solution?

Answer 4

(Calcium carbonate)

Question 5

Hydrochloric salts should not be mixed with alkaline/acidic (choose) fluids.

Answer 5

(Alkaline)

Question 6

Tetracyclines will precipitate in fluids containing what electrolyte?

Answer 6

(Calcium)

Question 7

The solubility and therefore absorption of what types of drugs is reduced by being administered with drugs that increase gastric pH (such as omeprazole, ranitidine)?

Answer 7

(Azole antifungals)

Question 8

Why will a patient who has had more doses of omeprazole compared to another likely absorb more omeprazole when it is dosed?

Answer 8

(Bc omeprazole autoregulates its own absorption by increasing stomach pH, omeprazole is less degraded in an less acidic environment so it is more available for absorption)

Question 9

What are some drugs that contain cations that chelate with drugs like fluoroquinolones and tetracyclines?

Answer 9

(Antacids and sucralfate, these are the examples she gave and I’m sure there are probably a ton more)

Question 10

What is the issue with administering CYP-450 inducers with CYP-450 substrate drugs?

Answer 10

(CYP-450 inducers increase CYP-450 activity = CYP-450 substrate drugs are cleared faster = less efficacy of those CYP-450 substrate drugs)

Question 11

Describe drugs that are more affected by CYP-450 induction.

Answer 11

(Those that undergo hepatic metabolism, lipid soluble drugs, and drugs with a low hepatic extraction ratio)

Question 12

(T/F) Enzyme induction typically occurs after 2-3 weeks of drug exposure (and therefore may also take 2-3 weeks to return to normal after removing drug exposure).

Answer 12

(T)

Question 13

What is microsomal enzyme inhibition?

Answer 13

(A competitive drug binds to an enzyme thus forming an inactive drug-enzyme complex)

Question 14

(T/F) Enzyme inhibition typically takes 1-2 doses of a drug (unless it is a metabolite of the drug that causes inhibition, then it will take a little longer).

Answer 14

(T)

Question 15

CYP-450 inducers decrease/increase (choose) the concentration of other drugs in an animal.

Answer 15

(Decrease bc they are being metabolized quicker (if they are metabolized by CYP450))

Question 16

CYP-450 inhibitors decrease/increase (choose) the concentration of other drugs in an animal.

Answer 16

(Increase bc they are not being metabolized by the occupied CYP-450)

Question 17

Of the following drugs, which are CYP-450 inducers vs inhibitors.

• Rifampin
• Cimetidine
• Azole drugs
• Phenytoin
• Erythromycin
• Phenobarbital
• Quinidine
• Chloramphenicol
• Griseofulvin
• Glucocorticoids

Answer 17

• Rifampin (Inducer)
• Cimetidine (Inhibitors)
• Azole drugs (Inhibitors)
• Phenytoin (Inducers)
• Erythromycin (Inhibitor)
• Phenobarbital (Inducer)
• Quinidine (Inhibitor)
• Chloramphenicol (Inhibitor)
• Griseofulvin (Inducer)
• Glucocorticoids (Inhibitors)

Question 18

If you were to give a patient a CYP-450 inducer (such as rifampin) and a CYP-450 inhibitor (such as erythromycin) to a patient, which would work first and lead to either the increase or decrease (choose) of the other drug?

Answer 18

(The inhibitor would work first because inhibition is fast (1-2 doses), this would increase the concentration of the inducer)

Question 19

Why are protein binding interactions considered insignificant and what are some possible exceptions to that insignificance? (this is a long answer, sorry)

Answer 19

(Few reasons → tho some drugs are known to displace other drugs from protein binding sites and increase the fraction of unbound drug, the concentrations in the plasma tend to stay the same and the unbound drug is just more easily eliminated, also for most drugs the amount of protein in the plasma greatly exceeds the concentration of the drug in the plasma and binding is rarely saturated = interactions that involve displacement of protein bound drugs are rare EXCEPT (possibly) severe hypoproteinemia or using super highly protein bound drugs)

Question 20

(T/F) An example of two highly protein bound drugs interacting with each other and leading to toxicity is cefovecin and carprofen.

Answer 20

(F, this has been proven wrong)

Question 21

What type of interaction is one that occurs when 2 or more drugs are administered to cause the same (agonist/agonist or antagonist/antagonist) or opposite (agonist/antagonist) effect in a single patient?

Answer 21

(Pharmacodynamic interactions)

Question 22

(T/F) The use of naloxone to reverse an opioid is a pharmacodynamic interaction.

Answer 22

(T)

Question 23

How should sucralfate and minocycline be co-administered orally and why?

Answer 23

(Minocycline (or any tetracycline) should be administered 2 hours prior to administering sucralfate and this is because of chelation; this can also affect fluoroquinolones)

Question 24

What is the purpose of administering fluconazole with methadone?

Answer 24

(Fluconazole decreases the first pass metabolism of methadone therefore increasing bioavailability of methadone)

Question 25

(T/F) Naltrexone has no effect when administered to dogs.

Answer 25

(T, should not be used to reverse opioids bc it is useless, it is useful for deterring owners from stealing their pets opioids (come on people))

Question 26

Why is it recommended to increase the keppra dose by 25% (maximum) when co-administering with phenobarbital?

Answer 26

(Bc phenobarbital increases the metabolism/elimination of levetiracetam (somehow, don’t need to know how) → Dr. D suggests starting at the normal keppra dose and increasing as needed to 25%)

Question 27

What is the main purpose of Zenalpha (medetomidine/vatinoxan)?

Answer 27

(Vatinoxan reverses the peripheral adverse effects of medetomidine (decreased cardiac output, hyperglycemia) without affecting the analgesia/sedation caused in the CNS (besides reducing the duration, you still get good analgesia/sedation it just doesn’t last as long))