(2.2) Pharmahodynamics

Question 1

What are the four types of drug-drug interactions?

Answer 1

• Pharmacokinetic
• Pharmacodynamic
• Drug-disease
• Drug-food

Question 2

How does pharmacodynamic often affected by drug-drug interactions? Give 5 major classes of drugs which do this.

Answer 2

Via actions on receptors

• Anticoagulants
• Antidepressants
• Antiarrhythmics
• Antibiotics
• Anticonvulsants

Question 3

Suggest 3 major diseases that affect drug-drug interaction. Each suggest an example how.

Answer 3

• Renal disease: -GFR -> -elimination, especially worsen by NSAIDs & ACEis
• Hepatic disease: - proteinsynthesis -> -metabolism, e.g. hypoalbuminea or cirhosis
• Cardiac disease: - organ perfusion & -GFR

Question 4

What are the two types of Adverse Drug Reactions? Explain their difference.

Answer 4

• On target: targeted receptors found in other tissues -> exaggerated effects
• Off target: also act on to receptor subtypes -> metabolites production / immune response

Question 5

How is Therapeutic Index calculated?

Answer 5

Toxic Dose (TD50) / Effective Dose (ED50)

Question 6

Suggest 4 drugs that have narrow therapeutic window

Answer 6

• Warfarin
• Digoxin
  Aminophylline
  Aminoglycosides

Question 7

What is p-glycoprotein?

Answer 7

ATP-dependent efflux pump, important in drug resistant cancer cells

Question 8

What is the affinity of a drug? How is it measured?

Answer 8

• Ability of a drug binds to its receptor

- By Kd (conc at which 1/2 receptors occupied)

Question 9

What is the potency of a drug? How is it measured?

Answer 9

• Overall response of a drug

- By EC50 (conc at which 1/2 max effect produced)

Question 10

What is the efficacy of a drug?

Answer 10

The maximal effects

Question 11

What is a Partial Agonist?

Answer 11

A drug that can’t produce a maximal effect even with full receptor occupancy

Question 12

Which drug should people avoid drinking Cranberry Juice and why?

Answer 12

• Warfarin

- Cranberry juice is a CYP inhibitor -> + risk of haemorrhage

Question 13

Suggest 4 drugs that bind to plasma albumin

Answer 13

• Warfarin
• NSAIDs
• Sulphonamides
• Tricyclic antidepressant

Question 14

What are the 4 major drug targets in the body?

Answer 14

• Receptors
• Enzymes
• Transporters
• Ion channels

Question 15

What is Specificity in terms of receptor binding?

Answer 15

The complementary of a drug and its receptors e.g. good drug only works on one receptor

Question 16

What is Selectivity in terms of receptor binding?

Answer 16

The ability to produce desired therapeutic effects, measured with specific therapeutic indices e.g. good selectivity has minimal side effects

Question 17

How should you start an initial dose for an

• overweight patient
• underweight patient

Answer 17

• Overweight: start at normal dose then maybe work up from there
• Underweight: start at

Question 18

Three drugs with volume of distributions of the followings, in which fluid compartments are they likely to be found?

• 0.12L/kg
• 0.26L/kg
• 3..4L/kg

Answer 18

• 0.12L/kg in Plasma only
• 0.26L/kg in Extracellular fluid (plasma + interstitial)
• 3..4L/kg in Extra+Intracellular