Gastrointestinal Tract Pharmac😍

Gastrointestinal Tract

Peptic Ulcer Disease (PUD)

Cause:

• Excessive stomach acid.

Treatment:

1. Acid Reduction:

• HCl Production:
• Parietal cells secrete HCl.
• Proton Pump (H+-K+-Pump) mediates acid secretion.
• Stimulated by:
• ACh (M1)
• Histamine (H2)
• Gastrin (CCK)
• Mnemonic: His Aching Gas
• Inhibited by:
• PGE1

Acid-Reducing Drugs:

PPI

• Mechanism:
• Irreversible inhibitors.
• "Hit and Run" drugs.
• Exert systemic effect (not local).
• Given with enteric coating.
• Pro drug → active in acidic medium

• Indications:
• DOC for PUD (any cause).
• DOC for GERD.
• DOC for Zollinger-Ellison Syndrome.

• Adverse Effects (long-term):
• Decreased Ca2+ (Osteoporosis).
• Decreased Vit B12 (Megaloblastic anemia).
• Increased infections.

2. Antacids:

• Fastest pain relief for PUD.

• Types:
• Al(OH)3:
• Causes constipation.
• A → constipation
• Mg(OH)2:
• Causes diarrhea.
• Multiple → Diarrhea

• Typically given in combination.

3. Ulcer Protective Drugs:

• Sucralfate:
• Mechanism: Polymerization (requires acidic pH < 4).
• Do not combine with antacids
• Inhibits absorption of other drugs (e.g., phenytoin).
• Maintain 120-minute gap between sucralfate and other drugs.

4. Anti-H. Pylori Drugs:

• Amoxycillin

• Metronidazole

• Clarithromycin

Triple Drug Therapy:

• Used for H. pylori associated PUD.

• Components: PPI + 2 Antibiotics
• C: Clarithromycin (Preferred therapy)
• A: Amoxycillin / Metronidazole
• P: PPI
• CAP regimen

• Duration: Given for 2 weeks.

Anti-Emetic Drugs

Chemotherapy Induced Nausea and Vomiting (CINV)

D2 Blockers

Sickness

• Morning sickness: Doxylamine + B6

• Sea sickness: Meclizine (Anti histamine)

• Motion sickness: Hyoscine (Anticholinergic)
• Hayyyooo

• Mountain sickness: Acetazolomide
• Counteract respiratory alkalosis with metabolic acidosis

CB1 agonist: (Cannabinoid 1 agonist)

• Dronabinol

• Nabilone

• S/E: Red shot eyes, Hypotension

Mechanism of Action for Laxatives

1. Increased Water in Intestine

• Osmotic Laxatives:
• Mannitol:
• 2nd line for constipation
• Used in Hepatic encephalopathy
• Polyethylene Glycol (PEG):
• DOC for IBS + constipation
• Loperamide → DOC for IBS

• Chloride Secretory Agents:
• Linaclotide:
• Activates Guanylate cyclase → ↑↑ cGMP → ↑↑ CFTR activity
• Lubiprostone:
• Laxative
• Activates Type II chloride channels
• PGE1 analogue
• Tenapanor:
• ⛔ Na+H+ exchanger
• Collegil povumbo → Lena de clothil Pro stone kandu Thampanoor vach → IBS vannu

NOTE

• Loperamide
• DOC in IBS - Diarrhea
• u Agonist:
• Don't cross BBB → Efflux by P-glycoprotein (MDR1 transporter) → No dependence

Drug	Indication	ㅤ
Plecanatide	Chronic Idiopathic Constipation (CIC) in adult	Pling → when constipated
Naldemedine	Opioid-induced constipation	Naltrexone → Opioid Similarly → Naldemedine
Tenapanor	Irritable bowel syndrome with constipation	Thampanoor poyapo IBS vannu
Telotristat	Severe diarrhea due to Carcinoid tumors	Tell to start the car (Telotristat → Carcinoid)

2. Increased Intestinal Contraction

• Bisacodyl, Senna, Cascara:
• Increase low-grade inflammation of the large intestine, leading to increased contraction.
• Effect is seen after 6-8 hours (usually taken as a night dose).
• Maximum 10 days of use (Short term Rx).

• Senna specific effects:
• Melanosis coli
• Pink/Yellow brown urine

• 5HT-4 Agonists:
• Mosapride
• Prucalopride

3. Increased Stool Bulk

• Probiotics: Beneficial microbes
• Lactobacillus
• Saccharomyces
• B. clausii

• Prebiotics: Dietary fibers
• Methylcellulose
• Psyllium husk
• Bran

4. Stool Softening (Least Effective)

• Docusate sodium (surfactant)

• Docusate calcium

• Mnemonic: Docusate → Prevent docking → soften stool

Anti Diarrheal

• IBS D → Loperamide → Opioid agonist

• Diphenoxylate-atropine: Opioid agonist
• With atropine to prevent misuse

• Enkephalinase inhibitor: Racecodotril

• 5HT3 antagonist: Alosetron