GI Difficult Drugs

Question 1

Loperamide

Answer 1

Prescribed to help diarrhoea and soft bowel movements.
Weak opioid (similar to pethidine) that DOES NOT penetrate CNS (no analgesia).
Reduces progressive smooth muscle contraction of bowel but increases non-progressive smooth muscle contraction = SLOWER PERISTALSIS --> more water absorbed

Use with caution in UC because the decrease in peristalsis can put the pt at risk of toxic megacolon

Question 2

3 types of laxative

Answer 2

Bulk Forming: fiber replacement helping to stimulate water movement from the gut wall into the lumen increasing bulk and softening. METHYLCELLULOSE
Osmotic: very similar encourage water to move into lumen and then hold it there. PHOSPHATE ENEMA (good for bowel prep before colonoscopy)
Stimulant: Act on the electrolyte channels of the gut wall to encourage electrolyte movement into lumen. Water follows increasing bulk and softening (Senna) - commonly given as suppository.

Question 3

Mesalazine and Sulfasalazine

Answer 3

These are amino-salicylates. They have anti-inflammatory and immunomodulatory effects due to their release of 5-ASA. They are hence FIRST LINE THERAPY in the treatment of UC. Sulfasalazine can also be used as part of DMARD treatment for RA.
Sulfasalazine’s sulfapyridine group can give adverse effects:
- GI UPSET, Headache, Thrombocytopenia, OLIGOSPERMIA, Renal impairment
DO NOT GIVE TO PEOPLE WITH ASPIRIN SENSITIVITY
Mesalazine comes as tablet with special coating to help resist gastric breakdown so active ingredient can be released in bowel.

Question 4

Metaclopramide and Domperidione

Answer 4

ANTI-EMETICS. Can be given prophylactically or therapeutically to ease sickness and nausea.
They are Dopamine2 (D2) receptor ANTAGONISTS. They block D2 being able to act on receptors in the ‘vomiting section’ of the medulla and hence stop the release of emetic factors into the blood.
They also block D2 receptors in the gut and so stop GI relaxation and importantly relaxation of the LOS.
SEs are all related to the medullary effects: they often cause DIARRHOEA and sometimes INVOLUNTARY MOVEMENTS as they act on parts of medulla other than vomiting section - these SEs are more likely if the patient is young or if they are on anti-psychotics or parkinson’s meds.
10mg dose usually IV can be injected if metaclopramide.