The effect of pH on drug absorption 5. Many drugs are absorbed into the blood through cells lining the stomach, the small intestine, or other epithelial tissues. This process involves movement of the drug molecule across the plasma membrane by direct diffusion. Since the interior of the plasma membrane is hydrophobic, the uncharged molecules cross the membrane faster than charged (ionized) molecules. If a drug contains an ionizable group, its absorption will therefore be dependent on the pH. Consider the absorption of the ionizable drug, morphine, shown below in its uncharged form. We will only focus on the ionization of the amino group of morphine (pKa = 8.2). НО.
The effect of pH on drug absorption 5. Many drugs are absorbed into the blood through cells lining the stomach, the small intestine, or other epithelial tissues. This process involves movement of the drug molecule across the plasma membrane by direct diffusion. Since the interior of the plasma membrane is hydrophobic, the uncharged molecules cross the membrane faster than charged (ionized) molecules. If a drug contains an ionizable group, its absorption will therefore be dependent on the pH. Consider the absorption of the ionizable drug, morphine, shown below in its uncharged form. We will only focus on the ionization of the amino group of morphine (pKa = 8.2). НО.
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![The effect of pH on drug absorption
5. Many drugs are absorbed into the blood through cells lining the stomach, the small
intestine, or other epithelial tissues. This process involves movement of the drug
molecule across the plasma membrane by direct diffusion. Since the interior of the
plasma membrane is hydrophobic, the uncharged molecules cross the membrane faster
than charged (ionized) molecules. If a drug contains an ionizable group, its absorption
will therefore be dependent on the pH. Consider the absorption of the ionizable drug,
morphine, shown below in its uncharged form. We will only focus on the ionization of
the amino group of morphine (pKa = 8.2).
НО,
H
HO..
N-CH3
morphine (neutral)
morphine (charged)](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F9e38577e-9620-4c07-818f-a04b4c1cdbce%2Fb631b03e-c42b-4863-88a6-f3e515e718c3%2Fqnnvrw8_processed.png&w=3840&q=75)
Transcribed Image Text:The effect of pH on drug absorption
5. Many drugs are absorbed into the blood through cells lining the stomach, the small
intestine, or other epithelial tissues. This process involves movement of the drug
molecule across the plasma membrane by direct diffusion. Since the interior of the
plasma membrane is hydrophobic, the uncharged molecules cross the membrane faster
than charged (ionized) molecules. If a drug contains an ionizable group, its absorption
will therefore be dependent on the pH. Consider the absorption of the ionizable drug,
morphine, shown below in its uncharged form. We will only focus on the ionization of
the amino group of morphine (pKa = 8.2).
НО,
H
HO..
N-CH3
morphine (neutral)
morphine (charged)
![a. In the neutral form shown above, is morphine in its HA or A¯ state?
b. On the diagram above, draw the charged form of morphine.
c. The pH in the stomach is approximately 2.0, and in the intestine approximately
7.4. Calculate what proportion of morphine will be in its neutral form in the
stomach and in the intestine (as ratio of neutral/charged species). Fill in the table
below with your answers and show your work.
neutral/charged morphine*
intestine
stomach
*note: this is either [HA]/[A'] or [A]/[HA], depending on your answers in (a) and (b)
d. Using your result in part (c) of this question, predict if morphine is absorbed more
efficiently in the stomach or in the intestine. Explain your reasoning.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F9e38577e-9620-4c07-818f-a04b4c1cdbce%2Fb631b03e-c42b-4863-88a6-f3e515e718c3%2F1cobx4n_processed.png&w=3840&q=75)
Transcribed Image Text:a. In the neutral form shown above, is morphine in its HA or A¯ state?
b. On the diagram above, draw the charged form of morphine.
c. The pH in the stomach is approximately 2.0, and in the intestine approximately
7.4. Calculate what proportion of morphine will be in its neutral form in the
stomach and in the intestine (as ratio of neutral/charged species). Fill in the table
below with your answers and show your work.
neutral/charged morphine*
intestine
stomach
*note: this is either [HA]/[A'] or [A]/[HA], depending on your answers in (a) and (b)
d. Using your result in part (c) of this question, predict if morphine is absorbed more
efficiently in the stomach or in the intestine. Explain your reasoning.
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