Pharmacology Flashcards
What is an agonist?
Drug that occupies receptor and activates a process
What is an antagonist?
Drug that binds to receptor and inhibits a process
What is a competitive antagonist?
Binds to receptor site (competes for same receptor)
What is a non-competetive antagonist?
Binds to a different site, changes shape or function of receptor preventing binding / effect (allosteric inhibition)
Define potency
Amount of drug required to produce given effect
Define efficacy
Maximal effect that a drug produces irrespective of concentration
Define TD50
Median dose required to produce toxic effect of 50% of species
Define LD50
Median dose required to produce lethal effect in 50% of species
What is tachyphylaxis?
Sudden decrease in response to drug (e.g. GTN)
What is a chemical antagonist and give an example?
Binds to a drug rendering it ineffective (protamine to heparin)
What is a physical antagonist and give an example?
Binds to drug to prevent absorption e.g. charcoal
What is a physiological antagonist and give an example?
Effect occurs through secondary physiological process e.g. glucocorticoids lead to increase in blood sugar
Draw a dose response curve showing agonist and effect of competitive antagonist
Adding an antagonist increases the amount of agonist required (shifts to right along log scale) to produce the required effect but does not affect the overall maximum response
Draw a dose response curve showing agonist + irreversible antagonist
Adding an irreversable antagonist decreases the maximum response (e.g. less efficacy)
Draw a dose response curve showing full vs partial agonist
Full agonist reaches full efficacy whereas partial agonist only produces a partial response. e.g tramdol vs fentanyl
What is a pro-drug and give an example?
Inactive precursor chemical that must be absorbed and converted to the active drug - e.g. codeine
Name 4 mechanisms of drug permeation
- Aqueous diffusion though tight junctions / aqueous pores 2. Lipid diffusion 3. Special carriers (for large molecules e.g. glucose, proteins) 4. Exocytosis / endo cytosis (e.g. blood brain barrier)
What is Ficks law
Concentration gradient x (area / permeability) / thickness (e.g. things that affect = concentration gradient / increased area = higher rate of diffusion higher permeability = higher rate of diffusion higher thickness = lower rate of diffusion
How does pH affect drug permeability? Explain how urine prevents reabsorption
Ionised drugs are polar and therefore have less ability to permeate membranes depending on pH. Urine has a lower pH and therefore more of the drug is ionised and less likely to pass back into the body via membranes
Is aspirin a weak acid or weak base
Weak acid (salicylic acid) - dissociates into aspirin anion and H+
Explain the following dose response curve - an irreversable antagonist is administered in increasing doses
In lower doses the maximum effect is preserved. As the concentration of the irreversable antagonist is increased all the available receptors are taken up and maximum effect is reduced
Name an example of a partial agonist
Buprenorphine (partially activates opioid receptors but does not produce full effect)
Name two examples of second messengers
cAMP and calcium
Drug A is more _________________ than Drug B
Effective (higher maximum response)
Drug A is more _________________ than drug C
Potent (lower dose required to achieve same response)
Define volume of distribution
Amount of drug in body related to concentration (e.g. amount of drug in body / concentration)
Define clearance
Rate of elimination over concentration
Define formula for elimination
Rate of elimination = CL x C (clearance x concentration)
3 factors affecting bioavailability
Absorption, first pass elimination, rate of absorption
Name an example of CYP inhibitor
Grapefruit juice, macrolides
Name an example of CYP inducer
Smoking, alcohol, St Johns Wart
