Hydrophobic drugs are typically what?

Hydrophobic drugs are typically what?

• A. Water soluble
• B. Lipid soluble
• C. Ionized at physiological pH
• D. Excreted unchanged by kidneys

Answer: (B)

Hydrophobic drugs are lipid soluble. When a compound is hydrophobic, it dissolves readily in fats and is poorly soluble in water, so it readily partitions into the lipid components of cell membranes. This allows it to cross membranes by passive diffusion, enabling rapid absorption from the gut, widespread distribution to tissues (including the brain), and entry into lipid-rich areas. Because they are not water-soluble, these drugs are usually not excreted unchanged by the kidneys; instead, they are commonly metabolized by the liver to more polar, water-soluble forms that can be eliminated. Ionization depends on the drug’s pKa and the surrounding pH, but many hydrophobic drugs are non-ionized at physiological pH, which further facilitates membrane crossing.

Hydrophobic drugs are lipid soluble. When a compound is hydrophobic, it dissolves readily in fats and is poorly soluble in water, so it readily partitions into the lipid components of cell membranes. This allows it to cross membranes by passive diffusion, enabling rapid absorption from the gut, widespread distribution to tissues (including the brain), and entry into lipid-rich areas. Because they are not water-soluble, these drugs are usually not excreted unchanged by the kidneys; instead, they are commonly metabolized by the liver to more polar, water-soluble forms that can be eliminated. Ionization depends on the drug’s pKa and the surrounding pH, but many hydrophobic drugs are non-ionized at physiological pH, which further facilitates membrane crossing.