Oral Biopharmaceutics

Question 1

What is biopharmaceutics?

Answer 1

Study of physical and chemical properties of drugs, route of admin and how they affect rate and extent of absorption

Question 2

Advantages of oral administration

Answer 2

*patient comfort and convenience
*easy to self administer
*prolonged and targeted release formulations available

Question 3

Where do veins leaving GI tract drain to?

Answer 3

Portal vein > liver for first pass metabolism

Question 4

What does the stomach do?

Answer 4

*reservoir for food
*process food > fluid chyme to aid absorption of nutrients from small intestine
*regulates food delivery to small intestine
*produces bacteriostatic acid
*produces correct pH for pepsin

Question 5

Is there much absorption in the stomach?

Answer 5

No
Little water, ions, drug molecules and ethanol

Question 6

What gastric secretions does the stomach produce ?

Answer 6

*acid- fasted state pH1-3, fed 4-6, 2hrs after food returns to 3
*gastrin- stimulates gastric acid production. Stimulated by peptides
*pepsin- secreted as pepsinogen. Type of peptidases that break down proteins to peptides (above pH5 pepsin denatured)
*mucus- protects stomach from auto digestion by pepsin-acid combo

Question 7

What factors affect gastric emptying?

Answer 7

*volume- increased load = increased emptying time
*type of meal ie carb, fat
*physical state of content ie liquid fasted, size of solids
*drugs ie opioids inhibit emptying

Question 8

Where does most absorption take place?

Answer 8

Small intestine (4-5 m long with large surface area and highly vascularised, villi/microvilli)
3 parts- duodenum, jejunum and ileum (longest)

Question 9

What is the function of the small intestine?

Answer 9

*mix resulting chyme with enzymes for digestion
*mix contents with intestinal secretions to enable absorption
*water absorption

Question 10

What are the small intestine secretions?

Answer 10

*pancreatic enzymes (for digestion)
*bile salts
*mucus
*bicarbonate (in response to food to regulate pH- buffer). pH of small instance around 6-8

Question 11

What is the influence of a small change in pH in the small intestine on drugs?

Answer 11

*implication for MR forms, especially EC drugs, as defined pH required for active drug release via dissolution of coating

Question 12

What is the function of the colon (large intestine)?

Answer 12

*limited absorption of drugs BUT good candidate for targeted and/ or sustained releases formulations I.e in ulcerative colitis
*absorbs water and lipids (potential lymphatic drug delivery)
*gut flora- metabolise some nutrients

Question 13

What is the function of the rectum?

Answer 13

*store stools
*outgoing vein- inferior haemorodial vein - only part of GI to bypass liver (superior and middle still drain into portal vein) - suppositories

Question 14

What is an example of a barrier to absorption?

Answer 14

Mucus- viscoelastic gel made of mucin, thicker in stomach

Question 15

How and when does food affect bioavailability of drugs?

Answer 15

• delays gastric emptying- liquid increases
  *changes pH
  *increased splanchnic blood flow
  *affects drug metabolism
  *may interact with drug

Question 16

How do liquids help with drug absorption?

Answer 16

*increase gastric emptying
*higher volumes help dissolution
*improves bioavailability
Most drugs taken with glass of water

Question 17

When would food intake enhance drug absorption?

Answer 17

*lipid soluble drugs- bioavailability increased with high fat content food

Question 18

What polymer is usually used for delayed release of drugs?

Answer 18

PLGA

Question 19

Difference between delayed release (prolonged) and sustained release?

Answer 19

*delayed release used to target certain body site or part
*sustained release doesn’t target a body part