Week 2 - Basic Pharmacodynamics Concepts + DIs Flashcards
Pharmacodynamics
- study of the effect of drugs in the body
- relationship between concentration of drug at the sit of action and the effect
Sigmoidal
concentration vs effect relationship
- can be delayed due to biomechanical processess invoked
efficacy
maximum response produced by a drug
potency
concentratiom or dose required to produce 50% of the drugs maximum effects
agonist
activates a receptor to produce a response
antagonsit
has receptor affinity but no efficacy and can prevent agnonists from activiating receptors
competivie antagonists
reduce the potency of a agnonist
non-competivite antagonist
reduce the efficacy of agnonists, normally do not affect their potency
Why do individauls vary in their response to a drug
physiologic - differences in the number or function of receptors
pharmacologic - variations in the concentration of drug that reaches the receptor at the site of action
pharmacokinetics
- study of the fate of drugs in the body
- absorption, distribution and elimination, metabolism and excretion
Influence of dose
toxic range: therapeutic failure (too high)
Therapeutic range: therapeutic success
ineffective range: therapeutic failure (too low)
Liklihood and significance of drug interactions (DI)
- 5-6% estimated incidence of DI if person taking 2 drugs - increases to 56% if taking 6 drugs, if taking 8 = 100%
- not all drug interactions = clinically significant
- potential clinical significance = when a therapeutic combination could lead to an unexpected change or complication in the patients condition
Susceptible patients
- poly-pharmacy patients and CAM users
- patients with hepatic and renal disease
- drugs with narrow therapeutic index
- patients on long etm therapy for chronic disease
- patients in ICU, transplant recipents, complicated surgical patients
- patients with more than one prescriber
- those who do not involve their prescriber with treatment
- elderly or critically ill
What is a drug interaction
“interaction is said to occur when the effects of one drug are changed by the presence of:
- another drug
- herbal medicine
- food, drink
- medical condition
- some environmental chemical agents”
Mechanisms of drug interactions
- mainly happen through pharmacokinetic or pharmacodynamic process
