Final Exam - Section I and II Flashcards
Describe a non-competitve antagonist?
An allosteric receptor interaction that can never be overcome by the agonist.
Describe a partial agonist?
Competes with the full agonist and produces a lower response than full agonist when all receptors are bound.
In the prescene of a full agonist, it acts as an antagonist. In the abscence of a full agonist, it acts as an agonist.
Describe physiologic antagonism?
Drugs that inhibit the effect of another drug without binding to the same receptor.
Acetylcholine opposes the effects of epinephrine
Insulin opposes gluccocorticoid hormones
Explain active (Ra) and inactive (Ri) receptor congigurations?
Receptors switch between Ra and Ri on their own, even in the abscence of a drug - favors Ri.
Agonist favors Ra and Inverse Agonist favors Ri
Describe an inverse agonist?
An agonist that has a greater affinity for the Ri state, which inactivates the receptor site. Reduces constitutive activity which may producing an opposing physiologic effect.
In clinical practice it is just an antagonist.
Antagonistic activity (beta blockers, H1/H2 blockers)
Correlate stereoisomerism and differences in drug effects
One enantiomer is typically much more potent than the other, they can elicit differing respones from the receptor.
one enantiomer fits better into the receptor than the other
How can a partial agonist also behave as an antagonist?
Partial agonists compete for the same receptors as the full agonist, preventing the full agonist from binding.
What is the distribution coefficient (Kd)?
The concentration of a drug when 50% of the maximal binding is achieved
What would a high Kd indicate?
That the drug has a low affinity for the receptor.
What does albumin mostly bind to?
Acidic drugs
What does a1-acid glycoproptein mostly bind to?
Basic drugs
What does lipoprotein mostly bind to?
Neutral drugs.
Compare the efficacy and potency of these drugs.
Drug B is the most potent drug, but drugs A,C, and D are more and equally efficacious. Potency of the drugs is such that B>A>C>D.
How can you calculate therapeutic index?
TD50 divided by ED50.
What does the therapeutic index indicate?
The safety of a drug. A high Ti means the drug is safer than a low Ti.
What charge will a weak acid with a pKa of 3.5 favor at a pH of 1.5 and 6.5?
At pH 1.5 it will favor the uncharged (protonated) from and at pH 6.5 will favor the charged (unprotonated) form.
What is the charge on a weak acid when it become protonated and unprotonated?
When protonated it becomes uncharged, when unprotonated it becomes charged.
Acids have protons to give, so when protonated become neutral.
What is the charge on a weak base when it becomes protonated and unprotonated?
When protonated it becomes charged, when unprotonated it becomes uncharged.
Bases readily accept protons, and take on their charge when protonated.
What does the henderson hasselbach equation tell us?
The pH at which the protonated and unprotonated forms are in equilibrium (or the pKa)
What is Volume of Distubution (Vd)?
The space available in the body to contain a drug. The higher the Vd the less it says in the blood and more it disturbutes into the tissues and vice versa.
Describe first order elimination?
Applies to most drugs, rate of elimination varies with concentration. **Clearance remains constant. **
Describe Zero order elimination?
Rate of elimination is constant. Clearance varies with concentration.
Occurs when ability to eliminate drugs is at max capacity.
All transporters are being used.
What is half life (T1/2)?
The time it takes to get drug in body to 1/2 of its original concentration.
How many half lives does it take to acheive full drug effect and full drug elimination?
4 1/2 lives to reach both full effect and full elimination.
What is steady state dosing?
Dosing the drug in a way that replaces the eliminated amount and still keeps therapetic effects.