Question

Which of the following affects the Glomerular filtration of a drug?

• A. \( \text{Lipid solubility} \)
• B. \( \text{Plasma protein binding} \)
• C. \( \text{Degree of ionization} \)
• D. \( \text{Rate of tubular secretion} \)

Hint:

Remember that the glomerulus filters blood based on size and charge. Large molecules (like protein-bound drugs) are not easily filtered.

Answer 1

The Correct Option is B

Glomerular filtration is a passive process in the kidneys where water and small solutes are filtered from the blood into Bowman's capsule. Only unbound (free) drug can pass through the glomerular capillaries. Drugs that are highly bound to plasma proteins (like albumin) are largely retained in the blood and are not efficiently filtered. Lipid solubility and the degree of ionization affect the reabsorption of drugs in the renal tubules rather than their initial filtration. The rate of tubular secretion is an active transport process that occurs after glomerular filtration and moves drugs from the blood into the renal tubules.