20 Questions
What is one of the factors that play a crucial role in the biological activity of drugs?
3D shape of the molecule
How is the fit of drugs onto macromolecules described in the text?
Continuous process
What can cause significant changes in biological activity?
Very slight changes in structure
What concept was used to explain why certain structural features produce predictable pharmacological actions?
Lock-and-key concept
What does the pKa represent in physicochemical measurements?
Negative logarithm of the equilibrium constant
In which direction does the equilibrium lie for a strong acid with a low pKa in water?
To the right
What does a high pKa value imply for a weak acid in water?
Equilibrium lies to the left
Why does hydrochloric acid with a Ka of 1.26 x 10^6 have essentially no unreacted HCl left in solution?
Large product of conjugate acid and base concentrations
Why is tropicamide buffered near pH 4 for eye drop administration?
To minimize discomfort for the patient
Which atom in indomethacin has acid-base properties in aqueous media?
Pyridine nitrogen
Why is indomethacin preferred in a suspension dosage form buffered at pH 4 to 5?
To maintain its water solubility
What is the dosage form of indomethacin used for intravenous administration to premature infants?
Salt form
What is the general rule for determining a very weak acid?
pKa 8 to 10
In terms of ionization, how does ephedrine HCl compare to free ephedrine?
Ephedrine HCl is a poor proton acceptor, while free ephedrine is a strong proton donor.
How can the drug's pKa value be utilized with respect to solubility in different media?
To increase solubility in water
How are acids categorized based on ionic form and conjugate base properties?
HA acids transform into un-ionized conjugate bases, while BH+ acids change to polar conjugate bases.
A chemical with a pKa value greater than 12 would result in which of the following properties?
Very weak acidic properties in water
If a chemical has a pKa of 5, what can be inferred about its conjugate base properties?
Weak acidic properties in water
Which type of acid would transition from un-ionized acids to ionized conjugate bases?
HA acids
How does free ephedrine (conjugate base) behave in terms of accepting protons?
It is an excellent proton donor
Test your knowledge on ephedrine HCl's pKa value and its properties as a proton donor and acceptor. Learn why the protonated form of ephedrine is a poor proton donor while free ephedrine is an excellent proton acceptor.
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