Medicine Interactions

Question 1

How can drugs interact?

Answer 1

Synergistically: combination antibiotics
Toxicity
Antagonism: antidote to overdoe
loss of effect

Question 2

How can drug interactions be described using pharmacokinetics and pharmacodynamics

Answer 2

Pharmacokinetics: Change in drug conc,by altering absorption, metabolism and elimination. Hard to anticipate

Pharmacodynamics: Alter drug effect, via receptors or not. Easy to anticipate based on known drug effects

Question 3

What is the time course of CYP inhibitors vs inducers?

Answer 3

Inhibitors: rapid increase in substrate conc. Time for max drug interaction determined by half life and time for steady state of inhibiotr and time for new steady state of substrate.

Inducers: slow decrease in conc as time is required to synthesize enzyme

Question 4

CYP3A4

Answer 4

be aware of it and that substrates include sildenafil, statins, cyclosporin.

Question 5

CY2C9

Answer 5

WARFARIN, do not give with fluoexetine and stuff, or amiodarone

Question 6

How could serotonin syndrome occur and how does it present?

Answer 6

On an SSRI and takes herbal tea with St Johns wart which also increases serotonin.

Agitation, ataxia, diarrhoea, fever, myoclonus, shivering

Question 7

Pharmacodynamic examples, shared receptor and effect

Answer 7

Receptor: donezepil and oxybutynin, will decrease donepezil. Also beta blockers and bronchodilators

Effect: aspirin and warfarin, more likely to bleed. ACE inhibitor, diuretic and NSAID. All reduce renal blood flow, renal failure