Pharmacodynamics Flashcards
Describe sites of action for drugs. (6)
Cell surface receptors Nuclear receptors Enzyme inhibitors Ion channel blockers Transport inhibitors Inhibitors of signal transduction proteins.
Explain why there may be some response when ligand concentration is 0. (2)
Constitutive action - random firing of the receptor when not stimulated by a ligand.
Describe the dose response curves for these classes of molecule. Complete agonist Partial agonist Competitive antagonist Non-competitive antagonist (12)
Curve to 100% response - agonists give 100% signal - often hyperbolic as not in log.
Curve to less than 100% response - partial agonists give less than 100% response. Often hyperbolic as not in log.
Curve to 100% response - competitive antagonists are surmountable with increasing concentrations of receptor or endogenous ligand. - often sigmoidal so given in log.
Curve to less than 100% - non-competitive antagonists are non-surmountable. - often sigmoidal as given in log.
Define drug selectivity. (3)
Give an example of a highly selective drug and why this is helpful. (2)
The more selective a drug is for its target, the less chance it will interact with different targets. This means less side effects.
Penicillin is selective for bacteria (cell wall synthesis) and so does not affect mammalian cells.
Define drug specificity. (2)
Give an example of a lowly specific drug and why this is unhelpful. (3)
Targeting drugs against specific receptor subtypes allow drugs to be targeted to a specific organ.
Salbutamol is not very selective when treating asthma, so it targets both beta one and two receptors, causing tachycardia as well as bronchodilation.
Define affinity. (2)
The tendency of a drug to bind to a specific receptor. Also known as Kd.
Define efficacy. (1)
The ability of a drug to produce a response.
Define potency. (3)
The dose required to produce the desired biological effect. The different doses required from different drugs to cause the same effect. Also known as EC50.
Describe the therapeutic index of a drug. (4)
The relationship between concentrations causing adverse effects and concentrations causing desirable effects.
= EC50(adverse) / EC50(desirable)
= toxic dose / effective dose
Describe the therapeutic window. (4)
The range of doses that can effectively treat a condition while remaining safe. The window is a large as the therapeutic index, and is a balance between the minimal effective concentration and the mimimun toxic concentration.
