Pharmacodynamics Flashcards
Explain Pharmacodynamics
- mechanisms of durg action
- drug receptors
- drug properties
- variation in drug response
Explain Drug action
Drug molecules bind to cells
resulting in a drug receptor combination
Explain Drug Effect
Biochemical and physiological changes as a consequence of drug action
What are the three sites of drug action?
- Extracellular receptors
- Cell membrane receptors
- intracellular receptors
Wat are some of the Drug receptors?
- Regulatory proteins
- enzymes
- transport proteins
- structual proteins
- mutisubunit ion channels
- G-protein coupled receptors
- Protein Kinases
- transcrption factors
Intracellular receptors are important for..?
hormone binding
which receptors are important or cytokine and peptide binding?
ligand-activated transmembrane enzymes
the model that reflects the actions of receptors best is?
the lock and key model as receptors are highly specific
explain E, Emax and E50
E: effect observed at concentraion
Emax: MAX response of drug, limited to availble receptors
EC50: conc. of drug that results in 50% of MAX effect
explain,
C, Bmax, and KD
C: conc. of free unbound drug
Bmax: total conc. of receptor sites
KD: conc. of free durg at which half-max binding is observed (Drugs infinity for receptor)
the dose response curve
answers Q’s about drug efficency, toxicity and potency
response is proportional to the number to receptors occupied therefore
concentration to reach max reponse will decrease as he number of receptors increases.
- which is the most potent drug?
- which drug has the lowest max efficency?
- Drug X
- Drug Y
comparision of the curves with a known full agonist tells what about the antagonist?
about its potency
Explain a full antagonist
ligand-receptor interaction results in no response at all
What is A B and C
A: Full agonist (results in a full response)
B: Partial Antagonist (results in a partial response)
C: Antagonist
What is a mixed agonist?
occurs when partial agonists compete with a full agonist to reduce Emax.
Explain a competitive antagonist
- the antagonist will bind to the receptor but no response
- is reversible
- will shift the dose curve to the right
- higher concentrations the drug are required to achieve the max efficency (ie potency decreases)
- can be overcome by adding more drug
- most antagonists are competitive
explain the antagonist causing this response
a non competitve antagonist
- Emax will be less than for antagonist alone
- formation of non-reversable bonds
- curve becomes more narrow due to a decrease in receptors
- few antagonists are non-competitive
what is
- an agonist
- an antagonist
- agonist –> mimics/ stimulates
- antagonist –> blocks (eg propanol beta-blocker, prevents adrenaline and decreases heart rate)
explain Drug tolerance
response is proportional to the number of receptors occupied
Explain Down-regulation and give an example
down regulation of number of receptors availble to down regulate response
e.g. in response to increased adrenaline
explain up regulation and how it relates to the need for some animals to be weaned off drugs
- involves the upregulation of receptors to return to homeostasis
- when HR is too low the receptors will be upregulated in response.
- also occurs when antagonists bind to receptors and more receptors are needed for normal function
- weaning off drugs –>
- the receptors will be upreguated in response to increased antagonists and once off drug (ie loss of antagonist) too many recptors are present causeing in the example of propanol cardiac arrest. therefore drugs must be weaned off.
Explain tachyphylaxis and give an example
- occurs when the body has a diminished response via an inhibitory feedback loop from:
- repeated administration
- Diminished responses to the same dose
- degree of tachyphylaxis is proportional to the degree of stimulus
- example:
- nicotine
- dobutamine
- metoclopramide
- nitroglycerine
