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Some examples from this set of practice questions
1.
1. What does the lipid-water solubility coefficient indicate about a drug?
Answer: The lipid-water solubility coefficient is the ratio of a drug\'s dissolution in lipid versus water. A higher coefficient indicates greater lipid solubility and better absorption, while a lower coefficient indicates less lipid solubility and poorer absorption. Drugs with structures like benzene rings, hydrocarbon chains, steroid nuclei, and halogen groups are more lipid soluble.
2.
How does the molecular size of a drug affect its absorption? and What is the effect of particle size on drug diffusion and absorption?
Answer: -Smaller molecular size allows for rapid absorption, typically through aqueous diffusion or lipid channels. Larger molecules require endocytosis or facilitated diffusion for absorption due to their size. - Larger particle sizes result in slower diffusion and absorption. Smaller particles diffuse and are absorbed more quickly.
3.
How does the degree of ionization affect drug absorption?
Answer: The ionization of a drug depends on its pKa and the pH of the medium. Acidic drugs are more unionized in acidic environments and are better absorbed in such conditions, while basic drugs are more unionized in basic environments and are better absorbed there.
4.
How does the interaction between drugs and food affect absorption?
Answer: Food can enhance or inhibit drug absorption. For instance, statins are better absorbed with food, while milk decreases iron absorption. Vitamin C boosts iron absorption, and phytates reduce it. Calcium salts interfere with iron and tetracycline absorption, and some acidic drugs may form non-absorbable complexes with cholestyramine.
5.
How does gastrointestinal mobility affect drug absorption?
Answer: Optimal GI mobility is necessary for effective drug absorption. Increased or decreased motility can alter absorption rates. Diarrhea accelerates peristalsis, reducing contact time and absorption, while constipation slows disintegration and dissolution, impairing absorption. Drugs like metoclopramide, bethanechol, and domperidone enhance gastric motility and absorption.
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