Pharmacology Flashcards
Definition of pharamcology
Study of drugs, pharmaceuticals, medicines
Definition of medicine
type of applied pharmacology in which doctors prescribe drugs
Definition of pharmacy
licensed profession of preparing and dispensing drugs
Why herbal remedies not very effective?
- Mixture of multiple ingredients
- At variable amounts
- Contaminants which might be toxic
Definition of drug
Active substance with a direct effect in diagnosis, cure, mitigation, treatment or prevention of disease
Definition of placebo
an inactive substance administered as though it is a drug but which has no therapeutic effect (other than pleasing the patient)
Important attributes of drugs
Purity
Potency
Efficacy
Variability
Selectivity
Safety
Bioavailability
Cost
How do tiny amounts of drug have powerful effects?
Bind transiently to command and control molecules in the body by lock and key
Types of drug targets
Ligand gated ion channels
GPCR
Kinase-linked receptors
Nuclear receptors
Enzymes
Voltage-gated ion channels
Transporters
What is agonist?
Substance reversibly binds to its receptor on the cell surface to produce a response by activating receptor signalling
2 types of agonist
Endogenous, drug
What is affinity?
Extent to which a drug binds to its receptor at a given concentration
(unbinding - related to chemical bond)
What is intrinsic activity (efficacy)?
Ability of a drug to illicit a pharmacological effect
What does parallel sigmoid curves indicate?
Both agonists share the same mechanism of action
What does wide therapeutic index means?
Very few people taking effective therapeutic dose will also experience toxic effects
Formula of therapeutic index
TD50/ED50
Definition of therapeutic window
Range of plasma drug concentrations within which a drug is working therapeutically without side effects
What is competitive antagonist?
Does not produce biological effect directly, but competes with agonist for binding to the receptor
Affinity and efficacy of competitive antagonist
Has affinity as it binds to the receptor but no efficacy as it doesn’t induce receptor signalling
Effect of competitive antagonist on potency, efficacy of agonist
Reduced potency and same efficacy
What is non-competitive antagonist?
Irreversibly occupy receptor’s active site, so agonist cannot elicit a maximum response
Effect of non-competitive antagonist on potency, efficacy of agonist
Reduced potency, reduced efficacy
What is pharmacokinetic antagonism
Drug interaction
- reduces concentration of the agonist by reducing absorption, distribution or increasing metabolism, excretion
What is physiological antagonism?
Two drugs or substances which have opposing physiological actions in the body acting via different receptors
What is spare receptors?
Remaining receptors when agonist produce maximal response by activating only a proportion of receptors
What is partial agonist?
Cannot achieve maximal response by occupying all available receptors (low efficacy, e.g. pindolol on beta-1 adrenergic receptors)
How drug acts on ion channels?
Acts as agonist or antagonists
e.g. anaesthetics blocking Na channels
How drug acts on enzymes?
Acts as inducer, inhibitor (prodrug, false substrate…)
e.g. aspirin inhibits cyclooxygenase
How drug acts on transporters?
Act allosterically, bind to carrier site or be a false substrate
e.g. SSRI (fluoxetine)
What is tolerance/tachyphylaxis?
On repeated administration, increasing doses need to be given for the same effect
(tachyphylaxis is fo fast)
Possible causes of tolerance
Receptor down-regulation, enhanced drug elimination…
