Pharmacodynamics Flashcards
what are the key concepts in pharmacokinetics?
Drug concentrations and Response
Affinity
Efficacy
Potency
What are the main effects drugs can have?
Depression
Stimulation
Destruction
Replacement
How can drugs work?
Some activate endogenous proteins - Agonist
Some antagonize, block or inhibit endogenous proteins - Antagonist
A few have unconventional mechanisms of action
Where do drugs work?
Cell surface receptors Nuclear receptors Enzyme inhibitors Ion channel blockers Transport inhibitors Inhibitors of signal transduction proteins
What are some different unconventional mechanisms of action of drugs?
Disrupting of structural proteins
e.g. vinca alkaloids for cancer, colchicine for gout
Being enzymes
e.g. streptokinase for thrombolysis
Covalently linking to macromolecules
e.g. cyclophosphamide for cancer
Reacting chemically with small molecules
e.g. antacid for increased acidity
Binding free molecules or atoms
e.g. drugs for heavy metal poisoning, infliximab (anti-TNF)
Tell me how agonists work.
They bind to a receptor and elicit the normal response of that receptor
Some drugs are partial agonist and so only elicit a partial response, or only partially bind
Tell me how competitive antagonists work.
They can fit into a receptor binding site but do not elicit a response, thus blocking the receptor from agonists or ligands of that receptor
The more agonist giving can still eventually increase the response, it will just take more agonist
Tell me how non-competitive antagonists work.
They bind to a site on a receptor different to the binding site causing a conformational change thus preventing any agonists from eliciting a response
No matter how much agonist you give once a non competitive antagonist has been giving there is a maximal response that can be elicited, once that has been reached no matter how much more agonists you give won’t elicit more of a response
What is an ideal drug? (and what do real drugs actually do?)
An ideal drug interacts at one site but not other sites and does not cause unwanted effects
Real drugs act at more than one binding site - collateral damage
What is drug selectivity?
The more the selective a drug is for its target, the less chance that it will interact with different targets and have less undesirable side effects.
e.g. Penicillin target
- Enzyme involved in bacterial cell wall biosynthesis.
mammalian cells do not have a cell wall, so penicillin
has few side effects.
What is drug specificity?
Targeting drugs against specific receptor subtypes often allows drugs to be targeted against specific organs
e. g. adrenergic receptors
- Heart beta1 receptors
- Lungs beta2 receptors
- More specific a drug acts the less action on other organ
What is drug affinity?
Defines the tendency of a drug to bind to a specific receptor type.
What is drug efficacy?
Ability of a drug to produce a response as a result of the receptor or receptors being occupied
Efficacy describes the maximum effect of a drug
What is drug potency?
Dose required to produce the desired biologic response
Potency describes the different doses of two drugs required to exact the same effect
What is the therapeutic index?
The relationship between concentrations causing adverse effects and concentrations causing desirable effects
EC50 (adverse effect) Therapeutic index= -------------------------------
EC50 (desired effect)
=Toxic dose/Effective dose
