Absorption Lecture 4

Question 1

Factors affecting drug absorption in the GIT include

Answer 1

1. GIT motility
2. Gastric emptying time
3. Intestinal motility
4. GI Blood flow
5. Effect of food

Question 2

Drug absorption may be affected by any disease that causes changes in:

Answer 2

• 1. Intestinal blood flow
• 2. GI motility
• 3. Gastric emptying time
• 4. Gastric pH (drug solubility)
• 5. Intestine pH (extent of drug ionization
• 6. Permeability of gut wall
• 7. Bile secretion (enterohepatic circulation)
• 8. Digestive enzyme secretion (break down of drug)
• 9. GI flora (GI transit time)

Question 3

Drugs that affect Absorption of other Drugs

Answer 3

1. Anticholinergic drugs, TCA & phenothiazines
2. Metoclopramide
3. Antacids
4. Proton pump inhibitors
5. Cholestyramine

Question 4

Nutrients that Affect Absorption of other Drugs

Answer 4

• Vitamin D : enhances calcium absoprtion in the duodenum
• Grapefruit Juice ( increase bioavaibility because it inhibits metabolism of most drugs)

Question 5

Effects of Parkinson’s Disease (advanced stage) on drug absorption

Answer 5

• Difficulty swallowing
• greatly dimisinished GI motility

Question 6

Patients on :

tricyclic antidepressants ( imiprimine, amitriptyline and notrityline) + antipshycotic drugs ( phenothiazines)

Answer 6

• Reduced Gi motility or even intestinal obstructions.
• May cause slower perstalsis in the GIT
• Slower stomach emptying
• Delays in Drug absoprtion with slow release products

Question 7

Acholorhydric Patients on drug absorption

Answer 7

• May not have adequate production of acids in the stomach → stomach HCl is essential for solubilizing insoluble free bases.
• Many weak base drugs that cannot form soluable salts will remain undissolved in the stomach when there is no HCl acid present so they cant be absorbed → salt forms cannot be prepared
• Drugs that are affected : Dapsone, itrconazole, and ketoconazole
• Can coadminister with OJ, colas, or acidic soda to facilitate the absorption of meds that require acidic environment.

Question 8

HIV-AIDS patients

Answer 8

• Decresded gastric transit time, diarrhea, and achlorhydria.
• Indinavir ( LTI ) requires a normal acidic environment or absoprtion. →optimal serum concentrations are critical

Question 9

CHF patients with persistent edema

Answer 9

• reduced splachnic blood flow and develop edema in the bowel wall
• Intestinal motility is slowed
• Drug Absorption is decreased
• Ex. Lasix has erratic and reduced oral absoprtion in patients with CHF

Question 10

Crohn’s disease ( inflammatory disease of the distal small intestine and colon)

Answer 10

unpredictable effect on drug absorption ( may be due to reduced SA and thicker gut wall for diffusion)

Question 11

Celiac disease ( inflammatory diseas affecting proximal small intestine)

Answer 11

• Increased rate of stomach emptying + increased permeability of the small intestine.
• Keflex absorption is increased in celiac disease

Question 12

Anticholinergic drugs

Answer 12

• Reduce stomach acid secretion
• ex. Propantheline bromide slows stomach emptying and motility of the small intesine.
• Cause delay in drug absoprtion.

Question 13

Antacids effect on other drugs

Answer 13

• Cimetidine : antacids reduce drug absoprtion
• Al,Ca, or Mg Antacids may complex ( chelate) with tetracycline, quinolones, and indinacir → decrease in drug absorption.
• Antacids should be taken 2 hrs before or 6 hrs after drug administration.