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Principles of Disease 16 > Drug-drug interactions > Flashcards

Flashcards in Drug-drug interactions Deck (23)
1

Discuss environmental factors which may predispose a patient to drug interactions

Food
Herbs
Drug intake
Alcohol intake

2

Describe patients who may be more susceptible to DDIs

• Polypharmacy (~8 drugs 100% chance of DDI)
• The elderly
• The young
• The critically ill
• Patients undergoing complicated surgery
• Those patients who have chronic conditions e.g.
o Liver disease
o Renal impairment
o Diabetes mellitus
o Epilepsy
o Asthma

3

What characteristics of a drug may make it more likely to cause a DDI?

Narrow therapeutic index
Potent or high dose
Known enzyme inducers or inhibitors
Protein or drug binding

4

Name some vegetables that cause DDIs with warfarin

o Alfalfa
o Asparagus
o Broccoli
o Brussel sprouts
o Cabbage
o Cauliflower
o Kale
o Lettuce
o Onions
o Spinach
o Turnip greens
o Watercress

5

Name some herbs that cause DDIs with warfarin

o Ginseng
o Green teas
o Melilot
o Tonka beans
o Woodruff

6

Name some miscellaneous agents that cause DDIs with warfarin

o Avocado
o Fish oils
o Liver
o Soybeans
o Papain

7

Define drug-drug interations

• A drug interaction is defined as the modification of a drugs effect by prior or concomitant administration of another Drug, Herb, Foodstuff, Drink
• A drug interaction has occurred when the pharmacological effect of two or more drugs given together is not just a direct function of their individual effects

8

What is the object drug in a DDI?

The drug whose activity is effected by such an interaction is called the “Object drug.”

9

What is the precipitant in a DDI?

The agent which precipitates such an interaction is referred to as the “Precipitant”.

10

Describe a useful DDI

o The treatment of Parkinsonism with carbidopa and levadopa
• Carbidopa is a dopa decarboxylase inhibitor and prevents the systemic side effects from levadopa

11

Describe some pharmacodynamic mechanisms of DDIs

o Agonist or antagonistic Interactions
o Additive or synergistic interactions
o Interactions due to changes in drug transport
o Interactions due to fluid and electrolyte disturbances
o Indirect pharmacodynamic interactions

12

Describe some absorption mechanisms that can cause DDIs

o Formation of insoluble complexes
o Altered PH.
o Altered bacterial flora e.g. OCP
o Altered GIT motility.

13

How can you avoid absorption defects in DDIs?

Wait 2-4hr before next dose

14

Name some drugs that are affected due to changes in bacterial flora

OCP
Digoxin

15

Name some classes of drugs that can delay gastric emptying

anticholinergics
tricyclic anti-depressants
opiates

16

Name some drugs that can increase gastric emptying

domperidone
metoclopramide

17

Name the two most important plasma proteins involved in drug-protein binding

o Albumin
o α1-glycoprotein

18

Name some drugs that inhibit cytochrome P450s

clarithromycin
erythromycin
cimetidine
ketoconazole
omeprazole
Calcium channel blockers (diltiazem)

19

What drugs increase the metabolism of ciclosporin?

Rifampacin and St Johns wort

20

Give an example of direct antagonism

Beta-1 selective beta-blockers such as atenolol will block the actions of agonists e.g. bronchodilators such as salbutamol

21

Give an example of indirect antagonism

o NSAIDs and antihypertensive medication – both have different effects on BP, leads to uncontrollable BP and potentially RF
o NSAIDs and treatment for heart failure

22

Describe some patient specific factors that increase the risk of DDIs

• Advanced ages
• Genetic polymorphisms
• Concomitant diseases
• Polypharmacy (~8 drugs almost 100% likelihood of DDI)

23

Describe some drug specific factors that increase the risk of DDIs

• Polypharmacy (~8 drugs 100% likelihood of DDI)
• Narrow pharmaceutical range
• Dose
• Multiple prescribing physicians
• Self prescription
• Prolonged length of stay