An overview of the lecture on important attributes of drugs including efficacy, potency and safety. Also covered is the action of agonists as drugs, selectivity and specificity of agonists and the idea of therapeutic index.
PHARMACOLOGY
What is a Drug?
What is a drug?
- A substance which when taken has a physiological or psychological effect on
the body and its functions
- An active substance with a direct effect in the diagnosis, cure, mitigation,
treatment or prevention of disease
What is a placebo?
- A substance with no therapeutic effect
- An inactive substance with no physiological effect, often used as controls
when testing new drugs
Important attributes of drugs
Efficacy – How big is the maximum response?
Potency – How big a dose is needed to produce the desired response?
Variability – What proportion of patients will have the desired response?
Selectivity – How effectively does the drug act on its molecular target and not on
other molecules?
Safety – What proportion of patients will have unwanted effects (U/E)?
Bioavailability – how much of an administered drug dose reaches its target?
Cost – how much does a course of drug therapy cost?
Command and control molecules (Lock and key)
Tiny amounts of drugs passing through the body can have such big effects because even
though they are mostly chemically inert, they bind transiently to command-and-control
molecules in the body because their molecular structures are complementary thereby
causing an effect.
Examples of command and control molecules:
Membrane receptors (for neurotransmitters, hormones etc)
Ion channels (that transmit nerve impulses)
Enzymes (that produce or degrade messenger molecules)
Nuclear receptors (that control gene activation)
Agonists
An agonist may be an endogenous substance or a drug that binds reversibly to a receptor
- Insulin acting on insulin receptors
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