Which two properties does the Biopharmaceutics Classification System (BCS) classify drugs by, and how do they influence oral absorption?

Which two properties does the Biopharmaceutics Classification System (BCS) classify drugs by, and how do they influence oral absorption?

• A. Solubility and permeability; high solubility and high permeability drugs are typically absorbed efficiently from the GI tract.
• B. Volume of distribution and clearance; high distribution and clearance enhance GI absorption.
• C. Protein binding and plasma albumin affinity; low binding improves absorption.
• D. Lipophilicity and molecular weight; high lipophilicity reduces GI absorption.

Answer: (A)

The key idea is that the Biopharmaceutics Classification System (BCS) groups drugs by how well they dissolve in the gut and how readily they pass through the intestinal lining. The two properties are solubility (solubility across the range of GI fluids and pH) and permeability (the ability to cross the intestinal epithelium). When a drug has high solubility and high permeability, it tends to be absorbed efficiently from the GI tract because it dissolves readily and can cross into the bloodstream quickly. If solubility is poor, dissolution becomes the limiting step, so even if the drug is permeable, not enough of it is dissolved to be absorbed. If permeability is low, even a well-dissolved drug won’t cross the gut wall effectively, also limiting absorption. Other factors like distribution, clearance, protein binding, lipophilicity, or molecular weight influence overall pharmacokinetics, but they are not the criteria used to classify drugs in the BCS.

The key idea is that the Biopharmaceutics Classification System (BCS) groups drugs by how well they dissolve in the gut and how readily they pass through the intestinal lining. The two properties are solubility (solubility across the range of GI fluids and pH) and permeability (the ability to cross the intestinal epithelium). When a drug has high solubility and high permeability, it tends to be absorbed efficiently from the GI tract because it dissolves readily and can cross into the bloodstream quickly. If solubility is poor, dissolution becomes the limiting step, so even if the drug is permeable, not enough of it is dissolved to be absorbed. If permeability is low, even a well-dissolved drug won’t cross the gut wall effectively, also limiting absorption. Other factors like distribution, clearance, protein binding, lipophilicity, or molecular weight influence overall pharmacokinetics, but they are not the criteria used to classify drugs in the BCS.