GI Disorders Drugs — Part 2

Primary effects of GI anticholinergics

Decreased GI/biliary/urinary motility and antisecretory effects.

Dicyclomine (Bentyl) drug class

Antispasmodic.

Dicyclomine (Bentyl) mechanism of action

Direct and indirect smooth muscle relaxation via ACh block and bradykinin/histamine antagonism.

Indications for GI anticholinergics/antispasmodics

IBS, PUD, diarrhea, spastic colon, ulcerative colitis, and diverticulitis.

Contraindications for GI anticholinergics/antispasmodics

Glaucoma, unstable CV status, GI/urinary obstruction, and myasthenia gravis.

Age contraindication for dicyclomine

Infants less than 6 months old.

Geriatric risk with GI anticholinergics

Increased risk of agitation, confusion, and delusions; requires lower doses.

Standout ADR of anticholinergics/antispasmodics

Anticholinergic psychosis (confusion, hallucinations, ataxia).

Preferred laxative classes for long-term use

Bulk-forming, hyperosmolar, and saline laxatives.

Why stimulant laxatives are avoided long-term

Can degenerate the nerve plexus, worsening constipation.

Indication for Psyllium

IBS and diverticular disease.

Indication for Polycarbophil

Constipation or diarrhea in IBS and diverticulosis.

Prophylactic use of mineral oil

Post-rectal surgery or MI to avoid straining.

Enema use of mineral oil

Fecal impaction.

Standout ADR of mineral oil

Lipid pneumonitis (aspiration risk, especially in reclining patients).

General contraindications for laxatives

Nausea/vomiting, appendicitis, fecal impaction, obstruction, or undiagnosed abdominal pain.

Sulfasalazine brand name

Azulfidine.

Sulfasalazine chemical structure

5-ASA linked to sulfapyridine by an azo bond.

How Sulfasalazine is activated in the body

Colonic bacteria cleave the azo bond to release active 5-ASA.

Sulfasalazine drug class & general actions

5-Aminosalicylate (5-ASA); anti-inflammatory and immunomodulatory.

Primary indications for Sulfasalazine

Acute IBD flares and remission maintenance.

Standout ADR of Sulfasalazine

Oligozoospermia (reversible male infertility).

Drugs with increased effects when taken with Sulfasalazine

Oral anticoagulants, oral hypoglycemics, and methotrexate.

Drugs with decreased effects when taken with Sulfasalazine

Iron, digoxin, and folic acid.

Contraindications for Sulfasalazine

Sulfonamide/salicylate allergy and intestinal/urinary obstruction.

Mesalamine brand names

Asacol, Lialda, Pentasa.

Difference between oral Mesalamine products

The drug-delivery mechanism (site of gut release).

Risk of discontinuing Mesalamine

Associated with a relatively high relapse rate.

Specific indication for Pentasa

Proximal intestinal Crohn's disease.

Specific indication for Lialda

Remission induction in active ulcerative colitis.

Standout ADR of Mesalamine

Rhinitis (respiratory symptom).

Drugs with increased effects when taken with Mesalamine

Oral anticoagulants, oral hypoglycemics, and methotrexate.

Drugs with decreased effects when taken with Mesalamine

Iron, digoxin, and folic acid.

Geriatric consideration for rectal Mesalamine

Elderly patients may have difficulty administering or retaining suppository forms.

Metoclopramide brand name

Reglan.

Metoclopramide drug class

Prokinetic / GI stimulant.

Metoclopramide mechanism of action

Sensitizes tissue to acetylcholine.

Physiological effects of Metoclopramide

Increases gastric contraction tone, relaxes pyloric sphincter, increases peristalsis, and increases LES tone.

Indications for Metoclopramide

Short-term GERD, diabetic gastroparesis, and chemo-induced/postop N/V.

Why Metoclopramide is restricted in GERD

Should not be used long-term due to high ADR risk.

Black-Box warning for Metoclopramide

Tardive dyskinesia.

Contraindications for Metoclopramide

GI hemorrhage, obstruction, perforation, pheochromocytoma, and epilepsy.

Administration timing for Metoclopramide

Take 30 minutes before meals and at bedtime.

Therapeutic step for IBD monoclonal antibodies

Step 3 immune-modifying agents.

Examples of IBD biologics (monoclonal antibodies)

Adalimumab, infliximab, vedolizumab, certolizumab, natalizumab, and ustekinumab.