What is the difference between pharmacodynamics and pharmacokinetics?
- Pharmacodynamics - what the drug does to the body
- Pharmacokinetics - what the body does to the drug
Drugs which act on receptors can be either _________ or ______________
What is affinity?
The strength at which a ligand will bind to its receptor
What is efficacy?
The ability of an agonist to evoke a cellular response
What is EC50?
The concentration of agonist that elicits half maximal response
This is the Michaelis-Menten constant
What is competitive antagonism?
The antagonist and agonist compete for the same binding site
What is non-competitive antagonism?
The agonist binds to the orthosteric site and the antagonist bings to a separate allosteric site
Activation cannot occur when the antagonist is bound
What is potency?
The effectiveness of a drug at a given concentration
How do competitive antagonists affect the concentration response curve?
Competitive antagonists cause a parallel rightward shift of the agonist concentration response curve with no depression of the maximal respons
How do non-competitive antagonists affect the concentration response curve?
Non-competitive antagonists depress the slope and maximum of the concentration response curve, but do not cause a rightward shift
Label A, B and C on the concentration response graph
What is the therapeutic window?
Any concentration of drug between the minimum effective concentration (MEC) and maximum tolerated concentration (MTC)
How is the therapuetic ratio calculated?
TR - MTC/MEC
Drugs with ____ therapeutic ratios are unsafe
When a drug is given by IV, how is the initial concentration calculated?
C0 = D/Vd
- D - dose (mg)
- Vd = volume of body plasma
The drop in concentration of a drug in the body over time depends on what?
The rate of removal or elimination (Kel)
What is first order kinetics?
Most drugs express this
It is when the rate of elimination is directly proportional to drug concentration
What is "clearance"?
This is the volume of plasma filtered clear of the drug in unit time
How is rate of elimination calculated?
Rate = Cl x Cp
- Cl - clearance
- Cp - plasma concentration
Rate of elimination is measured in l/hr
At a stead state the rate of drug administration will equal what?
The rate of elimination
(drug concentration remains constant)
Changing the rate of drug administration does not change the time to reach a steady state, it will change what instead?
It will change the concentration of the steady state
How many half lives does it take to reach a steady state?
What is a loading dose?
An initially higher administered dose given at the beginning f treatment.
It accelerates the time at which a steady state can be reached and when plasma concentration becomes adequate
How does a larger Vd affect half life?
It increases it
How can half life be shortened?
If Cl is reduced
What is zero order kinetics?
This describes drugs that are eliminated at a constant rate, regardless of their concentration
An increase in drug concentration will have no effect on the rate of elimination
(at very low concentrations some drugs may initially function at first order kinetics because concentration is the limiting factor)
What is the reason for some drugs functioning at zero order kinetics?
The enzyme that breaks them down has a Km that is lower than the concentration of the drug in the body
What is a ganglion?
A group of cells at which a synpase is present
Why is the sympathetic innervation of the adrenal gland unusual?
It is innervated by a preganglionic neurone
Acetylcholine is released
The adrenal gland acts as the postganglionic neurone, by releasing adrenaline
Where does the sympathetic outflow originate?
The sympathetic chain (thoracolumbar outflow)
Between the levels of T1 and L2