Page 96 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

 The duodenum

A common duct from the pancreas and the gallbladder enters into the duodenum.

The duodenal pH is about 6 to 6.5, because of the presence of bicarbonate that

neutralizes the acidic chyme emptied from the stomach.

The pH is optimum for enzymatic digestion of protein and peptide food.

Pancreatic juice, containing enzymes, is secreted into the duodenum from the bile duct.

▪ Trypsin, chymotrypsin, and carboxypeptidase are involved in the

hydrolysis of proteins into amino acids.

▪ Amylase is involved in the digestion of carbohydrates.

▪ Pancreatic lipase secretion hydrolyzes fats into fatty acid.

– The complex fluid medium in the duodenum helps to dissolve many drugs with

limited aqueous solubility.

– The duodenum is a site where many ester prodrugs are hydrolyzed during
absorption.

– The presence of proteolytic enzymes (protease) makes many protein drugs unstable
in the duodenum, preventing adequate absorption.

 The jejunum

It is the middle portion of the small intestine, between the

duodenum and the ileum.

– Digestion of protein and carbohydrates continues after

addition of pancreatic juice and bile in the duodenum

– This portion of the small intestine has fewer contractions

than the duodenum, and is preferred for in-vivo drug absorption

studies.

95