gi Flashcards
(20 cards)
METHYLCELLULOSE, ISPAGHULA HUSK, STERCULIA
Class: Bulk-forming Laxatives
Mechanism:
Indigestible substances absorb water → swell and increase stool bulk
Stimulate colonic stretch receptors → trigger peristalsis
Retain water → softer stools, easier passage
Uses:
Chronic constipation
IBS, diverticular disease (prevent stool stagnation)
Hemorrhoids, anal fissures (softer stools reduce strain)
Side Effects:
Bloating, flatulence (due to fiber fermentation)
Abdominal cramping
Notes:
Ensure adequate fluid intake to prevent obstruction
Delayed onset (12–72 hrs)
Safer for long-term use
SENNA, BISACODYL
Class: Stimulant Laxatives
Mechanism:
Directly stimulate myenteric plexus → ↑ peristalsis
Inhibit Na+/water reabsorption → ↑ fluid in lumen
Enhance prostaglandin/cAMP → ↑ chloride & water secretion
Uses:
Acute constipation
Bowel prep for colonoscopy/surgery
Short-term for chronic constipation
Side Effects:
Abdominal cramps
Diarrhea
Electrolyte imbalance (esp. with prolonged use)
Dependence and bowel atony (long-term use risk)
Notes:
Unsuitable for long-term use
LACTULOSE, PEG (Movicol, Macrogol), MAGNESIUM SALTS, SORBITOL, GLYCERIN (supp.)
Class: Osmotic Laxatives
Mechanism:
Poorly absorbed solutes draw water into colon via osmosis
Increase stool volume → stretch colon → stimulate peristalsis
Uses:
Chronic constipation (gentler option or resistant cases)
Bowel prep (e.g. PEG)
Short-term relief in acute constipation
Side Effects:
Dehydration
Electrolyte imbalance
Notes:
Lactulose: Non-absorbed sugar → fermented → acids → osmotic effect
Glycerin used rectally (suppository)
PRUCALOPRIDE
Class: Prokinetic Agent / 5-HT₄ Receptor Agonist
Mechanism:
Selectively activates 5-HT₄ receptors on ENS → ↑ ACh release
Stimulates smooth muscle contraction → enhances peristalsis
Uses:
Chronic constipation in adults when other laxatives fail
Side Effects:
Decreased appetite, GI discomfort
Diarrhea, dizziness, fatigue, headache, nausea, vomiting
Rare: Suicidal ideation
Cautions:
Renal impairment – adjust dose
Monitor mood/mental health
Avoid in intestinal perforation, obstruction, severe inflammation
LOPERAMIDE (Imodium)
Class: Antimotility Drug
Mechanism:
Synthetic opioid that acts on mu-opioid receptors in the intestinal smooth muscle
Inhibits release of ACh and prostaglandins, reducing gut motility
Decreases frequency of peristalsis and slows transit time
Uses:
Rapid control of diarrhea symptoms
First-line treatment for fecal incontinence
Side Effects:
Constipation, bloating, abdominal discomfort
Notes:
Effective for managing diarrhea and fecal urgency
DISODIUM HYDROGEN CITRATE + GLUCOSE, POTASSIUM CHLORIDE + SODIUM CHLORIDE, POTASSIUM CHLORIDE + RICE POWDER, SODIUM CHLORIDE + SODIUM CITRATE
Class: Oral Rehydration Therapy
Mechanism:
Sodium-glucose co-transport mechanism enhances absorption of Na via SGLTs in the small intestine
Osmotic gradient draws water and electrolytes from the lumen into the bloodstream
Uses:
Diarrhea-induced dehydration (e.g. rotavirus, cholera)
Corrects electrolyte imbalances, prevents dehydration
Side Effects:
Electrolyte imbalance (in severe dehydration or underlying conditions)
Vomiting (in some cases)
Notes:
Essential for rehydration during acute diarrhea or gastroenteritis
BISMUTH SUBSALICYLATE (Pepto-Bismol)
Class: Antidiarrheal, Gastroprotective
Mechanism:
Coats the stomach lining, forming a protective barrier
Hydrolyzes to produce salicylic acid, which inhibits prostaglandin synthesis, reducing inflammation
Antimicrobial effect against H. pylori and bacterial toxins
Uses:
Diarrhea, dyspepsia
Unlicensed use for H. pylori
Side Effects:
Dark stools, constipation, tinnitus
Notes:
Useful for traveler’s diarrhea and mild GI discomfort
CINNARIZINE, CYCLIZINE, PROMETHAZINE
Class: Antihistamine (1st Generation)
Mechanism:
Blocks histamine receptors (H1) to reduce nausea and vomiting
Sedative effect reduces motion sickness and vertigo
Uses:
All causes of emesis (nausea/vomiting)
Side Effects:
Drowsiness, dry mouth
Notes:
Often used for motion sickness and nausea relief
METOCLOPRAMIDE, DOMPERIDONE, PHENOTHIAZINES, BUTYROPHENONES (Haloperidol)
Class: Dopamine D2 Receptor Antagonists
Mechanism:
Block D2 receptors in the chemoreceptor trigger zone and GI tract
Enhance ACh release, increasing GI motility
Uses:
Relief of nausea and vomiting
Chemotherapy-induced nausea (severe cases)
Side Effects:
Dry mouth, fatigue, constipation
Tinnitus, muscle spasm, restlessness
Notes:
Used in severe nausea, especially from chemotherapy
HYOSCINE
Class: Anticholinergic
Mechanism:
Blocks M1 muscarinic receptors in the CNS
Reduces parasympathetic activity, preventing abnormal signals from the inner ear
Uses:
Motion sickness
IBS-related nausea
Side Effects:
Dry mouth, blurred vision, drowsiness
Notes:
Often used for motion sickness prevention
APREPITANT, FOSAPREPITANT
Class: Neurokinin 1 (NK1) Receptor Antagonists
Mechanism:
Inhibits emesis induced by chemotherapy (cisplatin) via central actions
Enhances antiemetic activity of 5-HT3 receptor antagonists
Uses:
Treatment of nausea and vomiting after chemotherapy
Side Effects:
Fatigue, dizziness, diarrhea
Notes:
Often used in combination with other antiemetics for chemotherapy-induced nausea
NABILONE
Class: Cannabinoid Receptor Agonist
Mechanism:
Partial agonist of CB1 and CB2 cannabinoid receptors
Inhibits neurotransmitter release (e.g. glutamate, dopamine), reducing nausea and promoting appetite
Uses:
Anti-emetic for chemotherapy when other drugs are ineffective
Appetite stimulation (e.g. cancer-related cachexia)
Side Effects:
Drowsiness, dizziness, altered perception, euphoria or dysphoria
Impaired concentration and memory, headache
Notes:
Use in cases where standard antiemetics are ineffective
SODIUM BICARBONATE, CALCIUM CARBONATE (Rennie), MAGNESIUM HYDROXIDE (Milk of Magnesia), ALUMINIUM HYDROXIDE (Alu-cap)
Class: Antacids
Mechanism:
Sodium bicarbonate: Neutralizes acid, releases CO2 (bloating)
Calcium carbonate: Reacts with acid to form calcium chloride, water, and CO2
Magnesium hydroxide: Neutralizes acid, acts as an osmotic laxative (diarrhea)
Aluminum hydroxide: Neutralizes acid, forms aluminum chloride (constipation)
All increase gastric pH and denature pepsin
Uses:
Rapid relief of heartburn and non-ulcer dyspepsia
Side Effects:
Diarrhea, constipation, flatulence, stomach cramps, nausea, vomiting
Notes:
Best taken with food to prolong effect
Short-lived action; frequent dosing may be required
COMBINATION ANTACIDS (Aluminum + Magnesium, Calcium + Magnesium, Aluminum + Magnesium Trisilicate)
Class: Antacids
Mechanism:
Aluminum + Magnesium: Balances constipation (aluminum) and diarrhea (magnesium)
Calcium + Magnesium: Provides rapid and prolonged acid neutralization
Aluminum + Magnesium Trisilicate: Neutralizes acid and forms a protective barrier
Uses:
Rapid relief of heartburn and non-ulcer dyspepsia
Side Effects:
Generally similar to individual antacid components
ALGINIC ACID (+ Antacids)
Class: Alginates
Mechanism:
Forms a viscous mass with a high pH, trapping CO2 and air bubbles
This mass forms a barrier on top of gastric contents, reducing gastroesophageal reflux and protecting from acid irritation
Uses:
Symptomatic relief of heartburn and reflux-related symptoms in non-ulcer dyspepsia
DIMETICONE
Class: Antifoaming Agent
Mechanism:
Reduces surface tension of air bubbles in the stomach
Releases trapped gas
Uses:
Flatulence
GRANISETRON, ONDASETRON, PALONOSETRON
Class: 5-HT₃ Antagonists
Mechanism:
Block 5-HT₃ receptors centrally and peripherally, inhibiting serotonin release
Effective in preventing and treating nausea/vomiting caused by chemotherapy
Uses:
Chemotherapy-induced nausea and vomiting
Post-operative nausea and vomiting
Side Effects:
Constipation, dry mouth, fatigue
ANITIDINE, TAGAMET, CIMETIDINE
Class: H₂ Antagonists
Mechanism:
Block histamine receptors (H₂) in the stomach to decrease acid production
Uses:
Gastroesophageal reflux disease (GERD)
Peptic ulcers, upper gastrointestinal bleeding (in critically ill patients)
Over-the-counter for acid indigestion
Side Effects:
Less effective compared to PPIs; limited action on proton pumps
Cimetidine may cause drug interactions due to its CYP450 inhibition
Notes:
Used less frequently now as PPIs are more effective
PANTOPRAZOLE, OMEPRAZOLE, LANSOPRAZOLE, RABEPRASOLE
Class: Proton Pump Inhibitors (PPIs)
Mechanism:
Prodrugs that convert to active sulfenamide in acidic parietal cells
Irreversibly inhibits H/K-ATPase (proton pump), blocking acid secretion
Uses:
GERD, peptic ulcer disease (PUD)
H. pylori eradication (with antibiotics)
Prevention of NSAID-induced ulcers
Side Effects:
Headache, nausea, diarrhea/constipation, hypomagnesemia (long-term use)
Increased risk of infection, osteoporosis, vitamin B12 deficiency
Notes:
Irreversible effect → long-lasting suppression (24-48 hrs)
Long-term use should be monitored for side effects
OMEPRAZOLE + AMOXICILLIN (or clarithromycin) + METRONIDAZOLE
Class: H. Pylori Eradication Triple Therapy
Mechanism:
Combines PPI (e.g., omeprazole) with antibiotics (amoxicillin, clarithromycin, metronidazole) to eradicate H. pylori
Uses:
H. pylori eradication therapy
Side Effects:
Typical side effects from PPIs and antibiotics (e.g., nausea, diarrhea, potential for resistance)
Notes:
Essential for treating H. pylori infections associated with peptic ulcers
