Pharmacology: Henderson Hassalbach Flashcards
1
Q
oral drug pass through
A
- must pass through epithelial layer of stomach lining or small intestines
- and through endothelial cell layer of intestinal capillaries
2
Q
inhaled drugs pass through
A
- must pass through epithelial cell layer of alveoli to reach their target sites
- and in some cases through endothelial cell layer of pulmonary capillaries if they need to be distributed systematically
3
Q
topical drugs pass through
A
- administered directly to target site
- some designed to enter general circulation
4
Q
intramuscular/subcutaneous drugs pass through
A
- bypass epithelial layers
- must pass through endothelial layer of capillaries to enter blood
5
Q
IV drugs pass through
A
- bypass both cell layers and are administered directly into systemic circulation
6
Q
which drugs can pass through the cell? why?
A
- hydrophobic
- uncharged
- because it the lipid bilayer is hydrophobic
7
Q
weak acids
A
- protonated (hydrophobic) in low pH
- deprotonated at high pH (negatively charged)
8
Q
weak bases
A
- protonated in low pH (positively charged)
- deprotonated (hydrophobic) at high pH
9
Q
what determines whether a drug will be charged or not?
A
- the pH of the surrounding environment
10
Q
which form of the drug is hydrophobic?
A
- the uncharged form
11
Q
pKa
A
- the pH at 50% of the molecule is protonated and 50% is unprotonated
12
Q
can you determine if a drug is acidic or basic by its pKa?
A
- NO!
13
Q
HH for weak acids
A
[A-] = 10^pH-pKa
[HA]
14
Q
HH for weak bases
A
[B] = 10^pH-pKa
[HB+]
15
Q
pH trapping
A
- the pH dependent equilibrium that exists between charged and uncharged states of a drug drives its absorption because different body compartments are at different pHs
- when the drug goes into its hydrophilic form, it is unable to cross the membrane back to another body compartment so it is trapped in the blood by the difference in pH between two compartments
