GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
PPI Laxatives Bile Salt Binding Resins Aminosalicylates
suffix - prazole Bulk-forming • Cholestyramine • Sulfasalazine
• omeprazole • Psyllium • Colestipol • Mesalamine
• esomeprazole • Methylcellulose • Colesevelam
• lansoprazole • Polycarbophil
• dexlansoprazole Peptides Glucocorticoids
• rabeprazole Stool softeners • Somatostatin • Prednisone
• pantoprazole • Mineral oil • Octreotide • Prednisolone
• Glycerin • Budesonide
• Docusate AntiSpasmodics /
H2 Receptor antagonist Anticholinergics
suffix - tidine Osmotic • Dicyclomine Purine Analogs
• Cimetidine • MgOH (milk of magnesia) • Hyoscyamine • Azathioprine
• Ranitidine • Sorbitol • HNBB • 6-mercaptopurine
• Nizatidine • Lactulose • Hyoscine-n-butyl Bromide
• Famotidine • PEG (Polyethylene glycol)
5-HT3 Receptor Antimetabolite
Stimulants antagonist • Methotrexate
Antacids • Aloe suffix - setron
• Aluminum hydroxide • Senna • Alosetron
• Magnesium hydroxide • Cascara • Granisetron Anti-TNF (Tumor Necrosis
• Calcium carbonate • Bisacodyl • Palonosetron Factor)
• Sodium bicarbonate • Palonosetron suffix - mab
• Ondansetron • Infliximab
Chloride Secretion • Tropisetron • Adalimumab
Mucosal Protective Agent Activators
• Sucralfate • Lubiprostone Corticosteroids
• Linaclotide • Dexamethasone Anti-integrin Therapy
• Methylprednisolone • Natalizumab
Prostaglandin Analog
• Misoprostol Opioid Receptor Neurokinin (NK1)
Antagonist Receptor Antagonist Pancreatic Enzyme
• Methylnaltrexone • Aprepitant Supplements
Bismuth Compounds • Pancreatin
• Bismuth subsalicylate Antipsychotic Agents • Pancrelipase
• Bismuth subcitrate K+ 5-HT4 Receptor Agonist • Prochlorperazine
• Tegaserod • Promethazine
• Prucalopride • Olanzapine Bile Acid Agents
Cholinomimetic Agents • Droperidol • Ursodiol
• Bethanechol
• Neostigmine Opioid Agonist H1 Antihistamine
• Loperamide • Diphenhydramine Variceal Hemorrhage
• Diphenoxylate • Meclizine Medication
D2 Receptor Antagonist • Octreotide
•Metoclopramide Cannabinoids • Vasopressin (antidiuretic
(Substituted Benzamide) • Dronabinol hormone)
• Domperidone • also known as THC • Beta Blockers (-olol)
(Tetrahydrocannabinol)
GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
Physiology of Gastrointestinal System
➔ Everything starts from the vagus nerve CN10
◆ Found in the cranial part which is part of the parasympathetic which permits digestion.
➔ When you eat food, your brain will stimulate your vagus nerve to release the neurotransmitter which is the Ach.
◆ Acetylcholine will activate the ECL cells and Parietal cells which are found in the GI Tract (mouth, esophagus,
stomach, small & large intestine, anus, liver, pancreas, gallbladder) but let's focus more on the stomach side.
➔ Ach will go to the preganglionic to bind with nicotinic receptors. In the preganglionic Ach binds with the muscarinic and
nicotinic receptors.
◆ In this case, the Ach binds to the muscarinic receptors (M2 receptors) of the ECL and Parietal cells.
➔ Ach will also bind to the G cell in order to release Gastrin. Once it is released to the bloodstream, it will bind with Gastrin
receptors of the ECL cell and Parietal cell.
◆ Once gastrin is bound with the ECL and Parietal cell, it will increase calcium.
◆ Muscarinic receptors and Gastrin receptors increase/release calcium when stimulated.
● M2 receptors - Acetylcholine
● Gastrin receptors - Gastrin
➔ In an ECL cell, the gastrin receptor will bind to the gastrin itself, and will release HISTAMINE.
◆ Histamine will bind with the histamine receptors of the Parietal cell called H2 Receptors.
➔ Parietal cell contains 3 types of receptors (Muscarinic, Gastrin, and H2/Histamine receptors)
◆ Once histamine binds to the H2 receptors of the parietal cell, it will convert into a secondary messenger which is
the cAMP (Cyclic Adenosine Monophosphate) with the help of the ATP.
◆ The presence of cAMP and Calcium in the parietal cell will now make the PROTON PUMP which is also called as
H+/K+ ATPase pump.
◆ Hydrogen (positive particle) will then go out from the H+/K+ ATPase pump and will fuse to the Chlorine ions
(negative particle).
● The chloride ions will just appear to the area where Hydrogen ions were released through a passive
diffusion from other parts of the body.
● Once they fuse, it will create Hydrochloric acid (HCl) which is the stomach acid.
GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
*So once you take in your food, your vagus nerve will be stimulated to follow the mechanism above in order for you to form HCl.
*HCl is dangerous, it may cause ulceration. That is why your stomach has protective barriers called the MUCOSAL BARRIERS.
How does our body stop the production of HCl?
➔ Not all the time the body will release HCl. The D-cell is involved with the inhibition of HCl release.
➔ The vagus nerve will stimulate the D-cell to send a message (via Ach) that there is too much H+ in the body. It will now
release SOMATOSTATIN.
➔ Somatostatin will now bind to the somatostatin receptors of the G-cell to inhibit the release of gastrin leading to the
reduction of acidic release.
◆ The medications for the Acid-peptic Diseases will involve in this mechanism
Antacids
➔ Its function is to NEUTRALIZE the acid in your stomach.
➔ ACID + BASE -> SALT + H2O
➔ Substances with Hydroxides or Bicarbonates are usually BASES
➔ Substances with H+ are usually ACIDS
➔ Products with CO2 gas will make the patient fart frequently.
Histamine 2 Receptor Inhibitor (H2 Receptor Antagonist)
➔ These medications are selectively binding to H2 receptor antagonists in your parietal cell.
➔ The H2 receptor is crucial in the formation of HCl or stomach acid. Once it is blocked, there would be no secondary
messenger for the proton pump leading to its decreased production. There will still be acid but a lesser amount.
◆ The calcium produced by gastrin and muscarinic receptors can still help the proton pump to release a minimum
amount of hydrogen ions.
➔ Recommended for fasting or during the night. When fasting, the stomach still releases acid, because there is gastrin
present in the bloodstream leading to its binding with the gastrin receptors in the ECL cell which helps the production of
histamine.
◆ Gastrin does not need to be stimulated by food intake unlike Muscarinic receptors.
➔ When sleeping, there is still production of histamine to release small amounts of stomach acid.
➔ When there is an ulceration in the stomach, the presence of the HCl will increase the pain as it penetrates the wound.
◆ That is why H2 receptor drugs are taken by the patients with stomach ulcers
*Presence of food increases the gastrin content which helps the release of HCl. It is mainly due to the stimulation of the muscarinic
receptor through the Vagus nerve.
*Without the presence of food, there will be no acid secretion.
*When sleeping, there would also be less acid secretion.
➔ Kremil-S Advance contains Famotidine, which is an H2 receptor drug.
◆ Famotidine can help regulate stomach acid secretion
◆ Kremil-S itself is an antacid which will only neutralize the hyperacidity
● The antacid content is Calcium carbonate CaCO3 with Sodium bicarbonate NaHCO3.
◆ Kremil-S Advance is a combination of H2 receptor drugs and antacid
● The problem with this drug is the frequent farting due to the gas product of the drug.
GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
Proton Pump Inhibitor (PPI)
➔ The cAMP and calcium ions present in the parietal cell makes the Proton pump.
◆ omeprazole
◆ esomeprazole
◆ lansoprazole
◆ dexlansoprazole
◆ rabeprazole
◆ pantoprazole
➔ All of those have suffix-prazole
➔ Omeprazole 20 mg is an OTC medication, while Omeprazole 40 mg is the prescription medication.
➔ PPI can be used for fasting and with food, since it is the endpoint,
◆ No matter how many receptors are being triggered in the parietal cells, your proton pump will be inhibited,
● So there would be no release of HCl.
➔ PPI is also used in Gastrointestinal Surgeries.
◆ You do not want stomach acid to be exposed during surgeries because the materials will be degraded.
Antispasmodic Agents or Anticholinergics
➔ Inhibition of muscarinic receptors. There will be no calcium produced.
➔ Only the gastrin receptor and H2 receptor will continue the process of HCl secretion.
◆ Dicyclomine
◆ Hyoscyamine
◆ HNBB
◆ Hyoscine-n-butyl Bromide
➔ Spasm is the movement of your stomach. It is the excitatory movement of smooth muscles
◆ Your promoted digestion when you have a spasm, then HCl is released.
◆ Inhibition of muscarinic receptors will decrease HCl secretion.
Mucosal Protective Agent
➔ Sucralfate same MOA (mechanism of action) of bismuth compounds
◆ Will be used to help heal stomach ulcers.
➔ Stomach ulcers occur due to stress or bacteria.
◆ Stress ulcers can be prominent to students due to lack of sleep. Your body must have a regulation of the acid
process, lack of sleep causes the relaxation of the stomach which leads to the increase of acid secretion. Too
much stomach acid causes stomach ulcers.
● When you are awake, there is acid secretion
● When you eat, there is much acid secretion
● When you are asleep, there is less acid secretion
◆ Bacteria (Helicobacter pylori)
➔ Sulcralfate will release negatively charged ions
◆ It binds with the positively charged ions found on the wound to form a mucosal barrier.
◆ Once there is no barrier, it will worsen and may cause sepsis as the bacteria will go through systemic circulation
from the ulceration or wound.
GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
● Sepsis is the presence of bacteria in the blood circulation
◆ The body has a mechanism to heal ulcers in the stomach, but too much ulceration requires sucralfate medication.
Bismuth Compounds
➔ Has antibacterial properties and also creates a mucosal barrier.
➔ Also serves as antidiarrheal medication
◆ Bismuth subsalicylate
◆ Bismuth subcitrate K+
➔ Helicobacter pylori
◆ PPI
◆ Bismuth
◆ Antibiotic (Metronidazole and Tetracycline)
◆ PPI with Amoxicillin and Clindamycin
➔ Types of Ulcers
◆ Stomach ulcers - you will feel pain while eating
◆ Duodenal ulcers - you will feel pain after eating
➔ Doctors may provide pain medication to manage stomach or duodenal ulcers
➔ GERD (Gastroesophageal Reflux Disease) - increase pressure inside the stomach causes peristalsis from the stomach
towards the esophagus.
Prostaglandin Analog
➔ To promote or increase the number of prostaglandin inside the body because it is the defensive mechanism of the body
against ulcers.
➔ When you have acid diseases (GERD, Ulcers), your prostaglandins are typically low, so you need to take prostaglandin
analog medication.
◆ Misoprostol
➔ Additional number only
Cholinomimetic Agents
➔ Cholinergic agonist (parasympathetic) - rest and digest
◆ Increase in HCl production
➔ Increase receptor binding
◆ Bethanechol (choline esters)
◆ Neostigmine (carbamates)
D2 Receptor Antagonist
➔ Dopamine has several subtypes including D2 receptors.
➔ Sympathetic responses will occur when dopamine receptors are activated.
◆ Low HCl production
◆ No peristalsis
◆ No movement of stomach
➔ D2 receptor antagonists will help.
◆ Digestion increase
◆ HCl production increase
◆ Increase in peristalsis
➔ D2 Receptor Antagonists
◆ Metoclopramide (Substituted Benzamide)
◆ Domperidone
Laxatives
➔ For patients with constipation or non functioning peristalsis as it promotes peristalsis.
➔ Bulk-forming Laxatives - increases fecal size to provide pressure during defecation. Contraindicated for geriatic patients,
as forceful defecation is detrimental to elderly as it can increase blood pressure.
◆ Psyllium
◆ Methylcellulose
GENERAL PHARMACOLOGY
Module 7: Drugs Used in the Treatment of GI Diseases
◆ Polycarbophil
➔ Constipation does not necessarily mean that the patient is experiencing hardening and increased fecal size. It just means
that your body is not functioning well when it comes to smooth muscle during defecation.
◆ Peristalsis is compromised during constipation.
➔ Stool Softeners - promotes defecation by inhibiting the absorbance of water inside the feces. It will make feces flow in the
large intestine.
◆ Mineral oil
◆ Glycerin - is a type of suppository (another suppository medicine that is kinda out of topic is pediatric paracetamol)
◆ Docusate
➔ Osmotic - promotes outside pressure
◆ MgOH (milk of magnesia)
◆ Sorbitol
◆ Lactulose
◆ PEG (Polyethylene glycol)
➔ Stimulants - will help you poop
◆ Aloe
◆ Senna
◆ Cascara
◆ Bisacodyl
➔ Senokot Laxative is one of the most commercialized types of laxatives that is from a stimulant called Senna.
Opioid Receptor Agonist
➔ Promotes constipation - when you give loperamide, you will not defecate.
➔ For diarrheal patients
◆ Loperamide
◆ Diphenoxylate
Opioid Receptor Antagonist
➔ Inhibits constipation - promotes defecation
◆ Methylnaltrexone
