Gastrointestinal medicines affect hydration, electrolyte balance, bleeding, pain, nausea, bowel motility, infection and nutrition. In the emergency setting, an apparently simple symptom such as vomiting or abdominal pain can represent shock, obstruction, perforation, poisoning, gastrointestinal haemorrhage, pancreatitis or surgical disease. EMTs must know which medicines support physiology, which can mask danger and which require urgent referral.
This lesson is for EMT and nursing education. Always apply current Uganda Ministry of Health guidance, facility protocols, prescriber orders, product information and age-specific algorithms.
Learning outcomes
- Describe digestive-system targets including acid secretion, motility, emesis pathways, fluid absorption and intestinal inflammation.
- Classify antacids, proton-pump inhibitors, H2 blockers, antiemetics, laxatives, antidiarrhoeals, antispasmodics, pancreatic medicines and selected GI antimicrobials.
- Recognise and initially manage dehydration, upper-GI bleeding, acute vomiting, diarrhoea, cholera, constipation, obstruction, pancreatitis and hepatic emergencies.
- Select safe routes and monitoring: oral, buccal, rectal, intramuscular, intravenous and nasogastric/enteral routes.
- Identify red flags, contraindications, interactions, renal/hepatic dosing issues and when symptom relief must not delay referral.
- Calculate, administer, reassess and document GI medicines safely.
1. Digestive physiology and medicine targets
The gastrointestinal tract digests food, absorbs nutrients and water, stores contents and eliminates waste. The stomach secretes acid and intrinsic factor; the pancreas supplies enzymes and bicarbonate; the liver produces bile and metabolises medicines; the intestine controls motility, secretion and absorption. Enteric nerves, serotonin, dopamine, acetylcholine, histamine, prostaglandins and opioid receptors are common pharmacological targets.
| Target/pathway | Physiological effect | Medicine examples | Emergency relevance |
|---|---|---|---|
| Gastric proton pump | Final step in acid secretion | Omeprazole, pantoprazole, lansoprazole | Reduces acid injury and supports ulcer therapy; does not replace endoscopy in bleeding. |
| Histamine H2 receptor | Stimulates acid secretion | Famotidine and related drugs | Acid reduction; dose adjustment may be needed in renal impairment. |
| Serotonin/dopamine emetic pathways | Nausea and vomiting | Ondansetron, metoclopramide, prochlorperazine | Controls vomiting but can prolong QT, cause dystonia or mask surgical abdomen. |
| Opioid receptors in bowel | Slow motility and increase sphincter tone | Loperamide, codeine, morphine | Can worsen ileus, toxic megacolon or respiratory depression. |
| Intestinal chloride/water secretion | Stool fluid and diarrhoea | ORS, zinc, selected antisecretory medicines | Replacement of water and electrolytes is more important than suppressing stool frequency. |
| Colonic water and motility | Stool formation and defecation | Lactulose, macrogol, senna, bisacodyl | Choice depends on obstruction, hydration, impaction and cause of constipation. |
| Pancreatic enzymes and bile | Fat and nutrient digestion | Pancreatin, ursodeoxycholic acid in selected disease | Malabsorption and cholestasis need diagnosis rather than empiric emergency dosing. |
2. Practical classification of gastrointestinal medicines
| Group | Examples | Main role | High-risk concern |
|---|---|---|---|
| Antacids/alginates | Aluminium hydroxide, magnesium hydroxide, calcium carbonate, alginate | Short-term relief of acid symptoms | Electrolyte disturbance, constipation/diarrhoea and drug absorption interactions |
| Proton-pump inhibitors | Omeprazole, pantoprazole, lansoprazole | GORD, ulcer disease and selected GI bleeding protocols | Long-term nutrient/infection effects and masking of alarm symptoms |
| H2 blockers | Famotidine | Acid suppression | Renal accumulation and confusion in frail older adults |
| Antiemetics | Ondansetron, metoclopramide, prochlorperazine, promethazine | Nausea/vomiting from selected causes | QT prolongation, dystonia, sedation and masking of obstruction |
| ORS/IV fluids | Low-osmolarity ORS, Ringer’s lactate, saline | Dehydration and shock from GI losses | Fluid overload, sodium imbalance and incorrect mixing |
| Antidiarrhoeals | Loperamide, racecadotril where available | Selected non-bloody diarrhoea | Avoid in dysentery, high fever, ileus or suspected toxic megacolon |
| Laxatives | Lactulose, macrogol, senna, bisacodyl, glycerol | Constipation and hepatic encephalopathy (lactulose) | Obstruction, dehydration and electrolyte loss |
| Antispasmodics | Hyoscine butylbromide, dicyclomine | Selected smooth-muscle spasm | Anticholinergic toxicity, glaucoma, urinary retention and masking acute abdomen |
| GI antimicrobials | Metronidazole, rifaximin and others | Specific diagnosed or suspected infections | Resistance, alcohol interaction, neuropathy and renal/hepatic dosing |
3. Antacids, alginates and acid-suppression medicines
| Class | Mechanism | Useful role | Safety and interaction points |
|---|---|---|---|
| Antacids | Neutralise existing gastric acid | Rapid short-term dyspepsia relief | Separate from iron, tetracyclines, quinolones and other medicines; aluminium may constipate, magnesium may cause diarrhoea. |
| Alginates | Form a floating barrier over gastric contents | Reflux symptoms after meals | Check sodium load in heart/kidney failure and use according to product directions. |
| PPIs | Irreversibly inhibit the gastric H+/K+ ATPase | GORD, peptic ulcer, H. pylori regimens and selected bleeding protocols | Review prolonged use; hypomagnesaemia, B12/iron issues, enteric infection and interactions may occur. |
| H2 blocker | Blocks histamine-driven acid secretion | Alternative acid suppression | Renal dose adjustment; confusion and bradycardia are uncommon but important. |
3.1 Alarm symptoms and GI bleeding
- Dysphagia, odynophagia, persistent vomiting, weight loss, anaemia, haematemesis, melaena, palpable mass or progressive symptoms require medical evaluation rather than repeated self-treatment.
- In suspected non-variceal upper-GI bleeding, stabilise ABCDE, assess shock, obtain access and arrange urgent endoscopy. Do not allow a PPI dose to delay resuscitation or definitive care.
- Ask about NSAIDs, aspirin, anticoagulants, steroids, alcohol, liver disease and previous ulcers.
4. H. pylori and peptic ulcer medicines
H. pylori eradication uses a PPI plus selected antibiotics according to local resistance patterns and previous exposure. The exact regimen is a prescriber decision; incomplete courses increase treatment failure and resistance. Test-of-cure and avoidance of unnecessary NSAIDs are important.
| Component | Purpose | Teaching/safety |
|---|---|---|
| PPI | Raises gastric pH and supports antibiotic activity | Take as prescribed; may need a washout before some H. pylori tests. |
| Amoxicillin/metronidazole/clarithromycin or alternative | Eradicates susceptible H. pylori | Check allergy, interactions, pregnancy, QT risk and alcohol with metronidazole. |
| Bismuth where used | Protective and antimicrobial activity | Dark stools/tongue can occur; salicylate content may matter in bleeding risk. |
| Sucralfate | Forms a protective barrier over ulcer base | Separate from other medicines; constipation and impaired absorption are possible. |
5. Antiemetics
Vomiting may be caused by gastroenteritis, pregnancy, migraine, obstruction, intracranial disease, metabolic disturbance, poisoning or medication adverse effects. Treat the cause and hydration status; antiemetic choice should match the clinical picture.
| Medicine/class | Mechanism/role | Major cautions |
|---|---|---|
| Ondansetron | 5-HT3 receptor antagonist; useful for many acute nausea syndromes | QT prolongation, constipation and headache; correct severe electrolyte disturbance and review interacting QT drugs. |
| Metoclopramide | Dopamine antagonist with prokinetic action | Dystonia, akathisia, tardive dyskinesia and rare NMS; avoid in obstruction, perforation, GI bleeding or Parkinson disease unless directed. |
| Prochlorperazine | Dopamine antagonist; antiemetic and vestibular action | Sedation, hypotension, dystonia, QT prolongation and NMS. |
| Promethazine | H1 antihistamine with anticholinergic/antiemetic effects | Marked sedation, respiratory depression, anticholinergic effects and tissue injury with extravasation. |
| Domperidone | Peripheral dopamine antagonist in selected settings | QT/arrhythmia risk; contraindications and interactions must be checked. |
5.1 Antiemetic safety checklist
- Ask whether the patient has severe abdominal pain, distension, no flatus/stool, blood or coffee-ground vomit.
- Check pregnancy status, allergies, Parkinson disease, epilepsy, QT-prolonging medicines and renal/hepatic impairment.
- Assess hydration, glucose, electrolytes if available and aspiration risk.
- Choose the least sedating effective route; do not give oral medicine to a patient with unsafe swallow.
- Reassess vomiting, pain, abdominal findings and mental status; symptom relief does not exclude surgical disease.
6. Oral rehydration salts and fluid therapy
Diarrhoeal deaths are usually caused by dehydration and electrolyte loss. WHO recommends low-osmolarity ORS for most diarrhoeal dehydration; the glucose–sodium co-transport system continues to absorb water even during diarrhoea. Continue breastfeeding and age-appropriate feeding when possible. Severe dehydration, shock, altered consciousness or inability to drink requires IV/IO resuscitation and urgent referral.
| Clinical state | Management principle | Reassessment |
|---|---|---|
| No or mild dehydration | Frequent small sips of correctly mixed ORS, continued feeding and zinc for children according to guideline | Urine output, thirst, mucous membranes, pulse, mental state and stool/vomit losses |
| Some dehydration | Supervised ORS replacement; use spoon, cup or nasogastric route if safe | Repeat weight or clinical dehydration signs and monitor vomiting. |
| Severe dehydration or shock | Urgent IV/IO isotonic crystalloid according to age, weight and shock protocol; ORS as soon as safe | Perfusion, capillary refill, BP, pulse, respiratory signs, urine output and electrolytes. |
| Cholera/profuse watery stool | Rapid ORS/IV replacement, infection prevention, stool surveillance and antibiotics for severe disease per protocol | Frequent fluid balance; losses can become life-threatening within hours. |
6.1 Correct ORS preparation
- Use the exact packet in the exact volume of safe water stated on the label; too little water can cause dangerous hypernatraemia.
- Do not add extra sugar or salt, and do not mix with milk, juice or carbonated drinks unless the product instructions allow it.
- Use prepared solution within the manufacturer/WHO recommended time and discard contaminated leftovers.
- If the patient vomits, pause briefly and restart with small frequent sips; persistent vomiting requires clinical assessment.
7. Zinc and antidiarrhoeal medicines
Zinc supplementation in children reduces duration and severity of diarrhoeal episodes, but the dose and duration are age-specific. Loperamide reduces intestinal motility and secretion in selected adults with non-bloody diarrhoea; it is not appropriate for every diarrhoeal illness.
| Medicine | Appropriate role | Avoid or escalate when |
|---|---|---|
| Zinc | Childhood acute diarrhoea according to WHO/UNICEF or national protocol | Check age, formulation and vomiting; continue ORS because zinc does not replace rehydration. |
| Loperamide | Selected non-bloody diarrhoea in adults | Fever, blood/mucus, suspected invasive infection, ileus, inflammatory bowel flare or young child without specialist direction. |
| Bismuth subsalicylate | Selected acute diarrhoea or dyspepsia | Salicylate allergy, anticoagulation, active bleeding, renal disease or children with viral illness. |
| Antibiotics | Specific bacterial dysentery, cholera or other diagnosed indications | Do not use empirically for every watery stool; consider resistance and local guidance. |
8. Laxatives and constipation
| Class | Examples | Onset/role | Safety points |
|---|---|---|---|
| Bulk-forming | Fibre/ispaghula | Increase stool bulk over days | Require fluid; avoid in obstruction or severe swallowing difficulty. |
| Osmotic | Lactulose, macrogol, polyethylene glycol | Draw water into bowel; useful for constipation | Bloating, diarrhoea and electrolyte disturbance if excessive; lactulose also treats hepatic encephalopathy. |
| Stimulant | Senna, bisacodyl | Increase intestinal motility over hours | Cramping and electrolyte loss; do not use repeatedly without diagnosing cause. |
| Rectal | Glycerol suppository, enema | Local evacuation for distal stool/impaction | Trauma, bleeding, vagal response; avoid with obstruction or recent rectal surgery. |
| Opioid antagonists | Naloxegol and related specialist medicines | Opioid-induced constipation | May precipitate withdrawal or abdominal pain; specialist selection required. |
9. Hepatic encephalopathy and lactulose
Lactulose is metabolised by colonic bacteria to acids that trap ammonia and promote its excretion. In hepatic encephalopathy it is titrated to regular soft stools under medical supervision. Excessive diarrhoea causes dehydration, hypokalaemia and worsened confusion. Assess for infection, GI bleeding, constipation, sedatives, electrolyte disturbance and renal failure as triggers.
10. Upper gastrointestinal bleeding
Haematemesis, coffee-ground vomit or melaena may result from peptic ulcer, varices, gastritis, Mallory–Weiss tear, malignancy or anticoagulation. A normal blood pressure does not exclude early shock. Resuscitation and urgent endoscopic assessment take priority over symptom relief.
- Assess airway, breathing and circulation; consider aspiration risk and suction. Reduced consciousness with active haematemesis may require advanced airway support.
- Place the patient safely, obtain large-bore IV access where trained, monitor ECG/BP/SpO2 and send urgent transfer.
- Ask about anticoagulants, antiplatelets, NSAIDs, liver disease, alcohol, previous ulcers and last oral intake.
- Use isotonic fluid and blood products according to shock/bleeding protocol; avoid over-resuscitation in portal hypertension or heart failure.
- Do not give oral food, drink or tablets to an unstable patient. PPI, vasoactive medicines and antibiotics for variceal bleeding are specialist-directed.
- Document estimated blood loss, stool/vomit appearance, vital-sign trends, urine output and every medicine/fluid given.
| Possible cause | Clues | Medicine implications |
|---|---|---|
| Peptic ulcer/NSAID injury | Epigastric pain, melaena, NSAID use | Stop NSAID pending review; PPI and endoscopy are clinician-directed. |
| Variceal bleeding | Cirrhosis, massive haematemesis, abdominal distension | Urgent specialist vasoactive drug, antibiotic and endoscopic pathway. |
| Mallory–Weiss tear | Bleeding after forceful retching | Resuscitate and refer; antiemetic only after obstruction/perforation considered. |
| Anticoagulant-associated bleed | Warfarin/DOAC/heparin use | Record exact medicine and last dose; reversal requires hospital protocol. |
11. Acute abdomen, obstruction and perforation
Antispasmodics and antiemetics may make a patient feel better while a serious surgical condition progresses. Severe or localised pain, guarding, rebound, distension, persistent vomiting, obstipation, fever, shock or pain out of proportion require urgent surgical assessment.
- Keep the patient nil by mouth when obstruction or surgical abdomen is suspected.
- Give analgesia appropriately; pain relief does not prevent diagnosis when examination and reassessment are documented.
- Avoid laxatives and oral medicines in suspected obstruction or perforation.
- Monitor for sepsis and dehydration; arrange IV access, fluids and urgent transfer.
12. Pancreatitis and biliary disease
Acute pancreatitis may cause severe epigastric pain radiating to the back, vomiting, ileus, fever and shock. Gallstones and alcohol are common causes, but medicines, hypertriglyceridaemia, trauma and infection are possible. Treatment is supportive: analgesia, carefully monitored fluids, antiemetic therapy and early assessment for organ failure. Avoid NSAIDs when renal perfusion, bleeding risk or dehydration is concerning.
| Finding | Concern | EMT action |
|---|---|---|
| Persistent vomiting/ileus | Dehydration, aspiration and electrolyte loss | Airway precautions, IV access and antiemetic only after obstruction assessment. |
| Hypotension/tachycardia | Third-spacing, bleeding or sepsis | Monitored fluid resuscitation and urgent transport. |
| Jaundice/fever | Cholangitis or biliary obstruction | Sepsis pathway, cultures/antibiotics under protocol and urgent specialist review. |
| Hypoxia/confusion | Organ failure or aspiration | Oxygen to target, blood gases and advanced support. |
13. GI infections and antimicrobial stewardship
Gastroenteritis is often viral or self-limited; antibiotics are reserved for defined indications such as severe cholera, dysentery, selected traveller’s diarrhoea, confirmed pathogens, sepsis or immunocompromised patients according to local guidance. Unnecessary antibiotics cause adverse effects and resistance.
- Ask about travel, outbreaks, unsafe water, sick contacts, recent antibiotics, hospital exposure and immunosuppression.
- Isolate when infectious diarrhoea is suspected; hand hygiene and safe waste handling protect staff.
- Do not use antimotility agents in bloody diarrhoea, high fever, suspected C. difficile or toxic megacolon.
- Collect stool or blood specimens when indicated without delaying resuscitation.
14. Special populations
| Patient group | Extra risk | Practical implication |
|---|---|---|
| Infants/children | Rapid dehydration and weight-based dosing | Use low-osmolarity ORS, zinc and paediatric algorithms; avoid adult antidiarrhoeals. |
| Pregnancy | Altered motility, aspiration and medicine safety considerations | Check gestational age and use pregnancy-appropriate antiemetic/acid therapy. |
| Older adults | Polypharmacy, renal impairment, delirium and atypical presentation | Review anticholinergic burden, QT drugs, NSAIDs and dehydration carefully. |
| Renal disease | Reduced clearance and dangerous electrolyte shifts | Adjust H2 blockers, antibiotics and laxatives; avoid excess magnesium/phosphate. |
| Liver disease | Bleeding, encephalopathy and altered metabolism | Avoid excess paracetamol/alcohol, monitor sedatives and ask about lactulose adherence. |
15. Interactions and medication safety
| Combination/situation | Risk | Action |
|---|---|---|
| Antacid + tetracycline/quinolone/iron | Reduced absorption through binding or pH change | Separate doses according to product guidance and document the timing. |
| PPI + selected medicines | Changed absorption/metabolism; long-term nutrient effects | Review ongoing need and interacting drugs; use the lowest effective duration. |
| Ondansetron + other QT-prolonging drugs | Torsades risk, especially with low potassium/magnesium | Correct electrolytes and obtain ECG in high-risk patients. |
| Metoclopramide + antipsychotic | Additive dopamine blockade, dystonia or NMS | Avoid duplication and assess Parkinson disease. |
| Loperamide + opioids | Ileus, constipation and sedation | Do not suppress stool without establishing cause and hydration status. |
| NSAID + anticoagulant/steroid | GI bleeding and ulcer risk | Ask about all analgesics and seek alternative/gastroprotection guidance. |
| Lactulose excess | Diarrhoea, hypokalaemia and dehydration | Titrate to the prescribed target and monitor mental status/fluid balance. |
16. Clinical scenarios
A 2-year-old has frequent watery stools but is alert and able to drink. Start correctly prepared ORS in frequent small amounts, continue feeding/breastfeeding and arrange zinc according to the paediatric protocol. Escalate urgently for lethargy, poor drinking, sunken eyes, weak pulse or reduced urine.
An adult has profuse “rice-water” diarrhoea and weak rapid pulse. Begin rapid ORS/IV rehydration under protocol, apply infection-prevention measures and transfer urgently. Antibiotics may be required for severe disease but must not delay fluids.
A patient has melaena, dizziness and a history of ibuprofen use. Keep nil by mouth, assess shock and airway risk, establish monitored access, record anticoagulants/NSAIDs and arrange urgent endoscopy pathway. Do not reassure the patient because the first BP is normal.
A patient has colicky abdominal pain, distension, persistent vomiting and no flatus. Avoid oral medicines, laxatives and large unmonitored fluid loads; protect the airway, establish access and arrange surgical assessment.
A young patient develops neck spasm and upward eye deviation after metoclopramide. Recognise an acute dystonic reaction, protect airway, stop further dopamine-blocking doses and seek protocol-based treatment.
A cirrhotic patient is confused after constipation. Check glucose, infection, bleeding, sedatives and electrolytes; continue prescribed lactulose plan under clinician direction without causing profuse diarrhoea or dehydration.
17. Calculations and administration checks
For a weight-based medicine, dose = prescribed mg/kg × weight in kg. For liquid preparations, volume = required dose ÷ concentration. For ORS, the packet-to-water ratio must be exact. Check units, concentration, maximum daily dose, renal/hepatic adjustment, route, timing and the last dose already given.
18. Documentation and handover
Document onset and character of pain/vomiting/diarrhoea, stool or vomit appearance, hydration signs, abdominal findings, pregnancy status, allergies, medicine history, suspected trigger, medicine/fluid name and concentration, dose, route, time, response and adverse effects. Handover should state airway risk, haemodynamic trend, fluid losses, urine output and need for surgical, endoscopic or infectious-disease review.
19. Revision questions
- Explain why ORS works during diarrhoea.
- List signs of severe dehydration and shock.
- Why must ORS be mixed with the exact packet volume?
- When are zinc and antibiotics used in childhood diarrhoea?
- Compare antacids, alginates, PPIs and H2 blockers.
- List alarm symptoms in dyspepsia or reflux.
- Why should PPI treatment not delay endoscopy in a GI bleed?
- Compare ondansetron, metoclopramide and promethazine.
- Why can metoclopramide cause dystonia?
- When should loperamide be avoided?
- List dangerous causes of constipation with vomiting and distension.
- Explain lactulose’s role in hepatic encephalopathy.
- What are the main causes of upper-GI bleeding?
- Why are NSAIDs risky with anticoagulants?
- How should a suspected cholera case be managed before transfer?
- List medicine interactions that prolong QT.
- What are the red flags for acute abdomen or obstruction?
- Why are children and older adults high-risk for GI medicine errors?
- Which details belong in a GI medicine handover?
- Write a safe plan for a patient with persistent vomiting and hypotension.
20. Key takeaways
- Hydration, airway protection and diagnosis come before symptom suppression.
- Correctly prepared ORS is life-saving for most diarrhoeal dehydration; severe shock needs IV/IO resuscitation.
- Antiemetics can cause QT prolongation, dystonia or sedation and may mask obstruction.
- GI bleeding, obstruction, perforation and pancreatitis require urgent assessment; do not delay definitive care with oral medicines.
- Use antidiarrhoeals and laxatives selectively after excluding infection, obstruction and toxic megacolon.
- Always check NSAIDs, anticoagulants, pregnancy, renal/liver disease and recent doses.
21. Recommended references for further study
- Gastrointestinal Drugs – SlideShare teaching resource
- WHO: Diarrhoeal disease
- WHO: Oral rehydration salts
- NICE: Acute upper gastrointestinal bleeding
- NICE: GORD and dyspepsia
- WHO: Cholera