What is the general concept of Pharmacodynamics?
The study of biochemical and physiological effects of drugs on the body
Investigates mechanisms of drug action, including the molecular, cellular, and biological effects of the drug.
Define affinity in pharmacology.
Binding strength of a drug to a target
Affinity is crucial for understanding how well a drug interacts with its receptor.
Define efficacy in pharmacology.
Ability of a drug to elicit a response once bound to a drug target
Efficacy determines the effectiveness of a drug in producing a desired effect.
What does potency refer to in pharmacology?
Amount of a drug needed to produce a defined effect
Measured using the 50% maximal response value (EC50).
What is an EC50?
Concentration giving 50% response
Used to measure the potency of a drug.
What are agonists?
Endogenous or exogenous molecules that have affinity for and efficacy at a receptor
They elicit a biological response.
What is a partial agonist?
Drugs whose maximum response is lower than the largest a tissue or cell can give
Even when they occupy all available receptors, they have low efficacy.
What is the purpose of dose-response curves?
Quantitatively measure and compare drug efficacy and potency
Vital for drug discovery programmes and predicting safe therapeutic doses.
Describe the shape of a dose-response curve for an agonist.
May be represented as a hyperbolic curve
Accurate but problematic for comparing EC50 values.
What is a log-dose response curve?
Forms a sigmoidal curve
Allows for easier comparison of relative potency of agonists.
What characterizes full agonists?
Drugs whose maximum response is the largest a tissue or cell is capable of giving
They fully activate the receptor.
What are antagonists?
Molecules that have an affinity for a receptor to limit the effect of agonists, but lack intrinsic efficacy
They prevent agonists from eliciting a response.
What is reversible drug binding?
Most agonists and many antagonists bind reversibly to the receptor
Weak chemical bonds allow for this reversible interaction.
What happens in the presence of competitive antagonists?
The log concentration response curve for an agonist will be shifted to the right
The shift is parallel and can be displaced by increasing the concentration of the agonist.
What is the effect of non-competitive antagonists on the agonist response?
The maximal response to the agonist is reduced, and the curve is not parallel
They bind at another site, preventing the effects of stimulation by the agonist.
Summarize the difference between competitive and non-competitive antagonists.
- Competitive: Maximal response remains the same, curves shifted parallel
- Non-competitive: Maximal response reduced, curves not parallel
Competitive antagonists bind at the same site as agonists, while non-competitive bind at another site.
Potency vs Efficacy
Potency highest in sigmoidal curves to the left (X-axis)
Efficacy on shown on the (Y-axis)
