Most important factor affecting drug absorption in GIT-

Ans. is 'a' i.e., Lipid solubilityFactors affecting drug absorption from guto Following factors affect drug absorption :1. Aqueous and lipid solubility# More lipid soluble drugs diffuse quickly.# Hydrophilic drug cannot cross lipid membrane.2. Ionization of drug# Drugs are absorbed in unionized state as unionized state is lipid soluble.# Thus ionization of a drug decreases its absorption.3. Presence of 6P' glycoprotein# 'P' glycoprotein actively pumps drug out of gut wall cells back into the gut lumen.# So, increased expression of P glycoprotein is associated with decreased absorption of drug.4. First pass metabolism# First pass metabolism in gut wall decreases the absorption of drug.5. Presence of food# Presence of food dilutes the drug and retards its absorption.# Thus, most drugs are absorbed better if taken in empty stomach.6. Site of absorption# Absorption from stomach is slower, because the mucosa is thick, covered with mucus and the surface area is small while absorption from intestine is fast, because mucosa is thin and the surface area is large.# Thus, faster gastric emptying accelerates drug absorption in general.