Pharmacodynamics Flashcards
What is pharmacology?
The science of interactions of chemical compounds with biological systems
What does pharmacodynamics refer to?
Drug effects on the body
What does pharmakokinetics refer to?
Body’s effects on the drug
What does ADME refer to?
Absorption, Distribution, Metabolism, Excretion
Purpose of drug therapy?
To produce a characteristic effect by achieving adequate concentrations at its site of action while minimizing undesired effects
What is a side effect?
An unwanted or bothersome effect of a drug usually related to the main effect.
What is a toxic effect?
A harmful or adverse effect of a drug usually not directly related to the main effect
What is a placebo?
A formulation that is identical in appearance to the real product but without the active drug
Drugs can only modify ______ fxn.
Cullular
Name for the drug action you want
Therapeutic effect
Two examples of drug actions extracellularly.
Neutralization of excessive gastric acid by antacids
Heparin in preventing blood coagulation
Two examples of drug interactions intracellularly
Drugs to treat infections
Drugs used for cancer chemotherapy
Hormones such as estrogen
_____ largely determine the quantitive relationship between dose/conc. of drug and the pharmacologic effects
Receptors
Similarities and differences between agonists and antagonists.
Similarities – Bind to a specific receptor
Differences - agonists stimulate receptor action, antagonists do not
What is observed at saturable levels of drugs
Concentrations at which no further increase in response can be achieved with increasing concentration
In the law of mass action, what is the association rate constant a measure of?
Potency
What does the relationship between DR –> Effect measure
Efficacy
Rate of association =
(D)(R)(k1)
Rate of dissociation =
(DR) (k-1)
At equilibrium, Rate of Association=
Rate of dissociation
Dissociation Constant (Kd) =
(k-1)/(k1) = (D)(r)/(DR)
The dissociation constant is _______ to the affinity
Inversely proportional
Equation for Receptor Occupancy =
[(Drug Concentration)(Max # of Receptors)]/(Drug Concentration) + (Kd)
What does Kd refer to?
The drug concentration at which half of the receptors are occupied
Three assumptions of the law of mass action
- Binding is reversible
- D and R only exist as free and bound
- All receptor sites have equal affinity and are independent
What is potency?
The dose of a drug required to produce a particular effect of given intensity
What is affinity?
The ability of a drug to interact with the receptor
Relationship between affinity and potency?
Affinity is a determinant of potency
What is efficacy?
The biological response resulting from the drug-receptor reaction
A strong agonist has a ____ affinity and a _____ efficacy
high, high
What may limit maximal efficacy?
Toxicity
Who is more important as a drug – efficacy or potency?
Efficacy
What changes in effect are seen when a partial agonist is used?
Reduced response even at full receptor occupancy.
May competitively inhibit the response to a full agonist
Three major types of receptor antagonists?
Competitive
Mixed
Irreversible
What occurs in competitive antagonism?
Reversible/Equilibrium Competitive antagonism
Effect of a competitive antagonist on the log dose-response curve?
Shift to the right
What does receptor reserve refer to?
When the maximal response can be elicited by an agonst at a concentration that does not result in 100% occupancy of available receptors
What is a noncompetitive agonist?
An antagonist that produces its effect at a site of the receptor other than the site used by the agonist
Log dose-response curve response to a non-competitive antagonist?
Curve shifts to the rights and the slope/maximal response are progressively decreased
Log dose-resonse curve response to an irreversible antagonist?
Initially, right shift (like competitive)
As concentration increases, maximal response is diminished (like in noncompetitive inhibition)
Molecularly, how does irreversible antagonism tend to work?
Covalent reaction between the antagonist and the same site as athe agonist. The antagonist is difficult to remove and inhibition can persist even after removal.
Effect of positive allosteric activators?
Increased potency and/or efficacy
Define functional antagonism. give an example
Twi drugs influence a physiological system in opposite directions. No direct chemical interaction.
Acetylcholine decreasing BP while epinephrine increases it
Define chemical antagonism. Give an example.
A chemical reaction occurs between an agonist and an antagonist to form an inactive product.
Calcium containing antacids and tetracycline ABs
Cyanide and sodium nitrite
