Introduction to Molecular Pharmacology
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PHRM 3310
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79 Terms
the study of the actions & effects of drugs on living systems & the interaction of drugs with living systems
What are the two main divisions of pharmacology?
pharmacodynamics & pharmacokinetics
What is pharmacodynamics?
the study of drug actions at target (receptor sites) & the physiological/chemical/behavioral effects they produce
What does pharmacokinetics study?
how drug concentration changes as it moves through the different compartments of the body
What is the classic difference between pharmacokinetics & pharmacodynamics?
pharmacokinetics = what the body does to the drug & pharmacodynamics = what the drug does to the body
What is pharmacodynamics also described as?
mechanism of action (MOA)
how the drug produces its effects at the molecular level
it provides the basis for rational therapeutic uses & the design of therapeutic agents
a specific target protein
What are the 4 groups of functional proteins?
enzymes, ion channels, transporters, & receptors
they can increase or decrease the rate of enzyme-mediated reactions
What are the 5 major types of drug effects/actions?
stimulation, depression/inhibition, irritation/inflammation, replacement, & cytotoxic effect
What is an example of a drug with stimulation effects?
adrenaline stimulates the heart
What are examples of drugs with depression/inhibition effects?
quinidine depresses the heart
barbiturates depress the CNS
omeprazole depresses gastric acid secretion
replacing a missing substance in the body
What are examples of replacement therapy?
levodopa in Parkinson disease
insulin in diabetes mellitus
iron in anemia
a drug effect that kills cells/organisms
What are examples of drugs with cytotoxic effects?
antiparasitics
antibiotics
anti-cancer
the concentration achieved at the site of action/receptor
dosage, extent of absorption, metabolism/distribution to the site, & rate/extent of elimination
the higher the concentration at the site of action/receptor, the greater the potential response
how the drug gets into the body/blood
how the drug moves to different tissues or compartments
how the drug is broken down
how the drug leaves the body
a drug binds to a receptor to form a drug-receptor complex that produces an effect
proteins inside/on the surface of cells that mediate drug activity
specific ligands such as neurotransmitters, hormones, antigens, chemicals, or other substances
it triggers a response or signal in the cell
a molecule that binds to a receptor
What are the 2 general types of ligand function?
agonist & antagonist
What is an agonist?
a drug that mimics the endogenous/physiologic ligand to produce a similar response
What is an example of an agonist?
morphine is an agonist for opioid receptors
What is an antagonist?
a drug that blocks the usual ligand & inhibits the physiologic response
What is an example of an antagonist?
naloxone is an antagonist for opioid receptors
the measure of a receptor's ability to respond to a single ligand
physiologic responses not targeted or intended by the drug, leading to side effects
the ability of the receptor to distinguish between drugs; the drug's preference for one receptor type over another
the strength of attraction between the drug & its receptor
a lower dose requirement
the effect of a drug reflects the occupancy of its receptor site, sometimes
one drug molecule combines reversibly with one receptor
all receptors are identical & equally accessible to the drug
the magnitude of the response is proportional to the number of receptors occupied by the drug
the effective drug concentration does not change during the reaction
What is KD in the receptor occupancy context?
the equilibrium dissociation constant, shown by the relationship [D][R]/ [DR] = k2/k1=KD
What is the key idea linking pharmacokinetics & pharmacodynamics?
pharmacokinetics moves the drug to the site of action; pharmacodynamics begins when the drug binds to the target & produces a response
What does pharmacokinetics include?
absorption, distribution, metabolism, & elimination (A.D.M.E.)
What are the 2 types of curves used to plot dose-response relationships?
graded dose-response curve & sigmoid curve
What is a graded dose-response curve?
a plot of response vs. the drug concentraion/dose
What is a sigmoid curve?
a plot of the same data of a graded dose-response curve, but on a logarithmic concentration axis
What is the value associated with Bmax?
the maximal number of receptors bound
What is does Emax measure?
efficacy
What does EC50/ED50 measure?
potency
What is the value associated with EC50/ED50?
the dose/concentration at which effect is half maximal
What is the value associated with Emax?
maximal effect
What is the relationship between efficacy & potency?
the smaller the EC50/ED50, the greater the potency
What is the value associated with Kd?
the concentration at which 50% of receptors are bound
What does Kd mean?
dissociation constant
What does Kd measure?
the affinity of a drug to its binding site
What is the relationship between Kd & affinity?
the smaller the Kd, the greater the affinity of the drug for receptor
What is efficacy?
the greatest effect (Emax) an agonist can produce if the dose is taken to the highest tolerated level
What is potency?
the amount of drug needed to produce a specified effect
What is the therapeutic window?
the safe range between the minimum therapeutic concentration & the minimum toxic concentration of a drug
What is a full agonist?
a drug capable of fully activating the effector system when it binds to the receptors
What kind of affinity & concentration do full agonists have for the activated receptor conformation & what is the result?
high affinity and sufficiently high concentrations, resulting in all the receptors achieving the activated state
What is a partial agonist?
a drug that is not capable of producing the full effect, even when it has saturated the receptors
What kind of affinity do inverse agonists have for the inactive state of a receptor?
higher than for active state
What happens when an antagonist bonds to receptors?
it prevents agonists binding & block their actions
Antagonists bind to receptors, but produce what kind of effect?
none
What do neutral antagonists do?
bind with equal affinity to the Ri (inactivated) & Ra (activated) conformation; prevent binding by an agonist & any deviation from the level of constitutive activity
What are a competitive antagonists?
drugs that bind to, or very close to, the agonist receptor site in a reversible way without activating the effector system for that receptor
What is a noncompetitive antagonist?
a drug that binds reversibly/irreversibly at an allosteric site on the receptor
What is a neutral antagonist?
a drug that bonds to the receptor w/o shifting the ratio of activated receptor to inactivated receptors
When do spare receptors exist?
when maximal drug response (Emax) is reached at less than 100% occupation of receptors (Bmax)
What is the relationship between EC50 & Kd in a system with spare receptors & what does this indicate?
the EC50 is lower than the Kd, indicating that to achieve 50% of the maximal effect, less than 50% of the receptors need to be activated
What does EC50 < KD mean?
the full effect can be reached with <100% occupancy
What are the relationships when the full effect can be reached with <100% occupancy?
duration of effector activation > duration of drug-receptor interactions
number of receptors > number of effector molecules