Gastrointestinal Drugs for NEET PG Pharmacology: PPIs, H. pylori, ICMR GI Bleed Protocol, Antiemetics, Laxatives, IBD

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🎯 Exam priority: High. Expect: an upper GI bleed vignette, PPI adverse effects, H. pylori regimen, the antiemetic for chemotherapy, metoclopramide's boxed warning, lactulose in hepatic encephalopathy, and sulfasalazine in a young man.

CBME mapping: PH 6.1–6.5. Indian protocols: ICMR Acute GI Bleed (July 2020) and Constipation (July 2022) workflows.

Gut Drugs at a Glance

GI drugs: target and the key warning for each, from the drugs' prescribing labels. Drawn by TrackNation.

Acid and Ulcers

• PPIs (omeprazole, pantoprazole) block the H+/K+ ATPase of the parietal cell; acid secretion returns over 3–5 days after stopping. Long-term risks: C. difficile diarrhoea (especially in hospital), osteoporotic fractures, low magnesium (after ≥ 3 months), low B12 (after years). Avoid omeprazole with clopidogrel.

• H. pylori triple therapy (label): omeprazole 20 mg + amoxicillin 1 g + clarithromycin 500 mg, each twice daily for 10 days.

• Famotidine: H2 blocker. Misoprostol: prostaglandin E1 analogue that prevents NSAID ulcers but causes abortion and birth defects — never in pregnancy.

Upper GI Bleed (ICMR)

Nausea, Bowels and the Liver

• Ondansetron (5-HT3 antagonist): dose-dependent QT prolongation; serotonin syndrome with serotonergic drugs.

• Metoclopramide (D2 antagonist): boxed tardive dyskinesia — avoid more than 12 weeks; raises prolactin; not in GI bleeding, obstruction or perforation, or phaeochromocytoma.

• Aprepitant (NK1 antagonist): chemotherapy vomiting, with other antiemetics.

• Constipation (ICMR): fewer than three proper stools a week; laxatives include sodium picosulfate, bisacodyl, polyethylene glycol, lactulose and senna. Red flags include delayed passage of meconium (> 48 hours); if a rectal biopsy shows absent ganglion cells, the treatment is surgical (pull-through).

• Loperamide: boxed warning — torsades and sudden death at higher-than-recommended doses (misuse).

• Hepatic encephalopathy: lactulose is broken down by colonic bacteria, acidifying the colon and lowering blood ammonia; rifaximin (a rifamycin) reduces recurrence.

Inflammatory Bowel Disease

• Sulfasalazine splits into 5-ASA and sulfapyridine; it can cause oligospermia and infertility in men (reversible on stopping).

• Mesalamine (5-ASA): check kidney function at the start and during treatment.

• Infliximab (anti-TNF): boxed serious infections (test for latent TB first) and malignancy, including fatal hepatosplenic T-cell lymphoma, mostly with azathioprine or 6-mercaptopurine.

Traps the Examiner Sets

• Give a PPI to every upper GI bleed until varices are confirmed; add terlipressin/octreotide and ceftriaxone if variceal.

• Endoscopy within 24 hours of stabilisation.

• Metoclopramide: no more than 12 weeks (tardive dyskinesia).

• Misoprostol is an abortifacient.

• Screen for latent TB before infliximab.

Memory Hooks & Shortcuts

Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.

• 🧠 Bleed? PPI first, Pressor for varices, Prophylactic ceftriaxone — the ICMR upper GI bleed triad

• 🧠 PPI's long road: C-D-M-B — C. difficile, Density loss (fractures), Magnesium, B12

• 🧠 Metoclopramide: Twelve weeks, Then Trouble (TD) — tardive dyskinesia beyond 12 weeks

• 🧠 Miso Must not Mothers — misoprostol is contraindicated in pregnancy

• 🧠 Infliximab: Investigate Infection (TB) first — latent TB test before anti-TNF

• 🧠 Sulfa-Salazine Slows Sperm — oligospermia

• 🧠 No ganglia, go Pull-through — absent ganglion cells on rectal biopsy → surgery

Rapid-Revision Cards

• UGI bleed: all patients (ICMR)

  IV pantoprazole 80 mg, then 40 mg 12-hourly.

• Variceal bleed (ICMR)

  Terlipressin 2 mg then 1 mg 6-hourly (or somatostatin/octreotide) 3–5 d + ceftriaxone.

• Terlipressin don't

  Heart or peripheral vascular disease.

• Endoscopy timing

  Within 24 h of stabilisation.

• Transfuse in GI bleed

  Hb < 7 (< 9 with heart disease).

• After ulcer bleed

  PPI infusion 72 h, then 40 mg BD 4 weeks; test H. pylori.

• After variceal bleed

  Propranolol 20 mg BD to HR 60; repeat banding.

• PPI action

  H+/K+ ATPase; recovery 3–5 days.

• PPI long-term

  C. difficile, fractures, low Mg, low B12.

• PPI + clopidogrel

  Avoid omeprazole.

• H. pylori triple

  Omeprazole 20 + amoxicillin 1 g + clarithromycin 500, BD × 10 d.

• Misoprostol

  PGE1 analogue; NSAID ulcers; abortifacient.

• Ondansetron

  5-HT3; QT; serotonin syndrome.

• Metoclopramide

  D2; tardive dyskinesia > 12 wk; prolactin ↑.

• Metoclopramide don't

  GI obstruction/bleed/perforation, phaeo.

• Aprepitant

  NK1 (substance P) blocker; CINV.

• Loperamide

  Boxed torsades at high doses.

• Lactulose

  Colon acidified, ammonia ↓.

• Rifaximin

  Prevents overt HE recurrence.

• Sulfasalazine

  5-ASA + sulfapyridine; oligospermia.

• Infliximab

  Anti-TNF; TB test; HSTCL.

• ICMR laxatives

  Picosulfate, bisacodyl, PEG, lactulose, senna.

Sources

Facts in this article were checked against these documents.

• Standard Treatment Workflows: Acute Gastrointestinal Bleed in Adults, Parts A and B — Indian Council of Medical Research / Department of Health Research, MoHFW, July 2020

• Standard Treatment Workflow: Constipation — Indian Council of Medical Research / Department of Health Research, MoHFW, July 2022

• Prescribing labels: omeprazole, famotidine, Cytotec, ondansetron injection, Reglan, Emend, loperamide, Enulose, Xifaxan, Lialda, Azulfidine EN, Remicade, Sandostatin, Terlivaz — DailyMed, US National Library of Medicine, current labels, accessed November 2026 (link)

• Competency Based Undergraduate Curriculum, Pharmacology (PH 6.1–6.5) — National Medical Commission, 2024

Test Yourself: Practice Questions

Twenty-four questions in NEET PG style, most of them clinical vignettes.

Practice Questions (NEET PG pattern)

Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.

Q1. A 50-year-old with melena, pulse 110 and BP 88/60 arrives at a district hospital. Per ICMR, besides resuscitation, every such patient gets

• (a) oral famotidine

• (b) IV vitamin K

• (c) IV metoclopramide

• (d) IV pantoprazole 80 mg, then 40 mg 12-hourly

Q2. A man with alcoholic cirrhosis, ascites and large-volume haematemesis is suspected to have a variceal bleed. ICMR adds

• (a) terlipressin (or somatostatin/octreotide) plus IV ceftriaxone

• (b) aspirin

• (c) oral metoclopramide

• (d) IV heparin

Q3. Terlipressin should be avoided in a variceal bleed patient who has

• (a) cirrhosis

• (b) ascites

• (c) jaundice

• (d) coronary or peripheral vascular disease

Q4. After stabilisation, ICMR says every acute GI bleed patient should have

• (a) a CT scan only

• (b) endoscopy after 2 weeks

• (c) endoscopy within 24 hours

• (d) barium meal

Q5. After band ligation for varices, the patient is discharged on

• (a) omeprazole alone for life

• (b) nifedipine

• (c) propranolol 20 mg 12-hourly, increased to a heart rate of 60/min

• (d) aspirin

Q6. An elderly woman on omeprazole for 4 years has low magnesium and anaemia with low B12. The label explains

• (a) omeprazole causes hypercalcaemia

• (b) this is unrelated

• (c) omeprazole causes iron overload

• (d) long-term PPIs can cause hypomagnesaemia and B12 deficiency

Q7. A hospitalised patient on IV pantoprazole develops profuse watery diarrhoea. A PPI-linked cause to consider is

• (a) lactose intolerance

• (b) Clostridioides difficile infection

• (c) hyperthyroidism

• (d) laxative abuse

Q8. PPIs reduce acid by inhibiting

• (a) the H+/K+ ATPase of the parietal cell

• (b) gastrin release

• (c) muscarinic M3 receptors

• (d) H2 receptors

Q9. A man with a duodenal ulcer tests positive for H. pylori. The omeprazole label's triple therapy is

• (a) metronidazole alone for 3 days

• (b) famotidine + sucralfate

• (c) omeprazole alone for 8 weeks

• (d) omeprazole 20 mg + amoxicillin 1 g + clarithromycin 500 mg, twice daily for 10 days

Q10. A woman with arthritis on NSAIDs is offered misoprostol. She must be told it

• (a) can cause abortion and birth defects, so it is not for pregnancy

• (b) is an H2 blocker

• (c) causes constipation only

• (d) raises gastric acid

Q11. A patient on cisplatin is given high-dose IV ondansetron and an SSRI. Two risks to watch are

• (a) hypoglycaemia and hyperkalaemia

• (b) ototoxicity and nephrotoxicity

• (c) QT prolongation and serotonin syndrome

• (d) tardive dyskinesia and gynaecomastia

Q12. A diabetic woman on metoclopramide for gastroparesis for 8 months develops involuntary movements of the face and tongue. This is

• (a) a seizure from hyponatraemia

• (b) tardive dyskinesia (avoid > 12 weeks)

• (c) a hypoglycaemic attack

• (d) serotonin syndrome

Q13. Metoclopramide is contraindicated in a patient with

• (a) diabetic gastroparesis

• (b) GERD

• (c) phaeochromocytoma or GI obstruction

• (d) nausea after surgery

Q14. A man on metoclopramide develops galactorrhoea and impotence. The reason is

• (a) anticholinergic effect

• (b) H2 blockade

• (c) D2 blockade raising prolactin

• (d) 5-HT3 blockade

Q15. For highly emetogenic chemotherapy, a drug that blocks substance P is

• (a) metoclopramide

• (b) domperidone

• (c) ondansetron

• (d) aprepitant

Q16. A young man misusing very high doses of loperamide collapses. The label's boxed warning is

• (a) aplastic anaemia

• (b) torsades de pointes and sudden death

• (c) hepatic failure

• (d) pancreatitis

Q17. In a cirrhotic with hepatic encephalopathy, lactulose works by

• (a) killing all gut bacteria

• (b) bacterial breakdown acidifying the colon and lowering blood ammonia

• (c) blocking dopamine

• (d) stimulating the liver

Q18. To reduce recurrence of overt hepatic encephalopathy, the label-approved antibiotic is

• (a) vancomycin

• (b) metronidazole

• (c) ciprofloxacin

• (d) rifaximin

Q19. A 4-year-old has had constipation since birth with delayed passage of meconium; rectal biopsy shows absent ganglion cells. Per ICMR, definitive treatment is

• (a) thyroxine

• (b) lifelong laxatives alone

• (c) dietary fibre only

• (d) pull-through surgery

Q20. A 25-year-old man with ulcerative colitis on sulfasalazine and his wife cannot conceive. A drug cause is

• (a) infliximab

• (b) mesalamine-induced azoospermia

• (c) no drug cause

• (d) sulfasalazine-induced oligospermia (reversible)

Q21. Before starting infliximab for Crohn's disease, the patient must be

• (a) given a live vaccine

• (b) started on warfarin

• (c) tested for latent tuberculosis

• (d) given a PPI

Q22. A young man with Crohn's disease on infliximab plus azathioprine develops a fatal lymphoma. The label names

• (a) Hodgkin lymphoma only

• (b) MALT lymphoma

• (c) Burkitt lymphoma

• (d) hepatosplenic T-cell lymphoma

Q23. Sulfasalazine is split in the colon into

• (a) 5-aminosalicylic acid and sulfapyridine

• (b) mesalamine and prednisolone

• (c) olsalazine

• (d) aspirin and sulfa

Q24. A patient on clopidogrel after a stent needs acid suppression. The omeprazole label advises

• (a) no interaction

• (b) avoiding omeprazole with clopidogrel

• (c) stopping clopidogrel

• (d) doubling omeprazole

Active Recall

From memory: give the ICMR drug protocol for acute upper GI bleeding (ulcer and variceal), the mechanism and long-term risks of PPIs, the H. pylori triple regimen, the key warnings for ondansetron, metoclopramide, misoprostol and loperamide, how lactulose and rifaximin help hepatic encephalopathy, and the warnings for sulfasalazine and infliximab.