Pharmacology

Question 1

Diphenoxylate

Answer 1

Mu Opioid receptor agonist in bowel.
Reduces peristalsis. Constricts sphinter.

Treats: Diarrhoea

Anti-Motility

Question 2

Loperamide

Answer 2

Long acting anti diarrhoeal.
Binds Mu receptor agonist on smooth intestinal muscle. Recruits G-protein receptor kinases which leads to activation of downstream cascade that blocks enteric nerve activity.

Chronic Diarrhoea. Oral admin.

Does not cross BBB.

Question 3

Kaolin

Answer 3

Bulking agent. Adsorbent powder (water, toxins, bacteria).

Hydrated Aluminum Silicate.

Question 4

Ispaghula husk

Answer 4

Bulk forming LAXATIVE to relive constipation by increasing faecal mass and inducing peristalsis.

^ bulk > ^ stretch receptor firing

Question 5

Lactulose

Answer 5

Laxative.
Broken down by Saccharolytic enzymes - resulting in lactic acid, formic and acetic acid. The volitale environment results in gas formation, increased peristalsis, and increases water content of stool.

Question 6

Senna

Answer 6

Stimulate laxative.
Activates myenteric plexus.

Question 7

Bisacodyl

Answer 7

Deacetylated into active form BHMP in intestine. BHMP can stimulate parasympathetic nerves of colon.

Relives occasional constipation.

Question 8

Docusate

Answer 8

lncreases water and fat content of stool.

Relives constipation of hard/dry stool and opioid induced.

Question 9

Allopurinol

Answer 9

Xanthine oxidase inhibitor.
Hypoxanthine structural analogue.

Increases reutlization of hypoxanthine/xanthine (purines) which causes feedback inhibition of de novo purine synthesis. Resulting in decreased urine and serum concentrations.

Question 10

Hydrocortisone

Answer 10

steroid

Question 11

Betamethasone

Answer 11

steroid

Question 12

Fludrocortisone
(Mineralocorticoid)

Answer 12

Increases Na+ channels on apical side of collecting duct & Na/K-ATPase on basolateral side.

Treats addisons.

Question 13

Beclomethasone

Answer 13

steroid (anti inflammatory)
Treats: UC (pills), Asthma atk (inhaled), psoriasis/dermatitis (cream).

Question 14

Process of Drug metabolism

Answer 14

Phase 1: Hydrolysis/Oxidation.
Phase 2: Conjugating enzymes (adding substance to metabolite to make substance less toxic (detoxification)).

Phase 1: CYP450 (needs Fe+3)
Phase 2: Hepatocytes add Cysteine/Glycine/Sulphur to make toxin more polar and less reactive. Glucuronidation is most common reaction - secreted in bile and urine.

Phase 3: Biliary excretion only if MW > 200kDa.

Question 15

Impaired Drug Metabolism

Liver disease and drug metabolism

Answer 15

Risk factors:
- Decreased hepatic blood flow.
- Decreased enzyme function.
- Decreased plasma protein binding (increases circulating drug).
- Decreased bile production.

Question 16

Paracetamol Overdose

Answer 16

CYP450 (CYP2E1) pathway becomes main pathway.
Resulting in NAPQI formation.
NAPQI is detoxified by GLUTATHIONE (when depleted NAPQI binds hepatocytes > oxidative stress > mitochondrial dysfunction > immune activation).

Treated with Acetylcystenine.

More pronounced in CENTRILOBULAR region (next to central vein) due to higher [CYP2E1].

Question 17

Azathioprine

Answer 17

Inhibits purine synthesis.

Question 18

Sulphalazine

Answer 18

Anti-inflammatory/immunosuppresive.

Used in UC and Crohns.

Contraindicated in PPI use.