Medicines acting on specific body systems

Medicines play a big role in modern healthcare, providing solutions to a wide range of diseases and disorders. The human body is a network of interconnected systems, each with its functions and challenges. To address these challenges, pharmacologists have developed drugs that act on specific body systems , ensuring targeted and effective treatment for various conditions.

These medicines are designed to interact with specific organs, tissues, or biochemical pathways, either by enhancing normal physiological functions or by correcting pathological imbalances. For example, cardiovascular drugs regulate heart function and blood pressure , while respiratory drugs help manage conditions like asthma and chronic obstructive pulmonary disease (COPD) . Similarly, gastrointestinal drugs address issues such as acid reflux, ulcers, and irritable bowel syndrome , and endocrine drugs help manage hormonal imbalances like diabetes or thyroid disorders .

Peptic Ulcer Disease (PUD)

Peptic ulcer disease develops when there is an imbalance between mucosal protective substances such as mucus and bicarbonate, and destructive substances like acid, H. pylori bacteria, and pepsin. Drugs used in the treatment of peptic ulcer disease include:

• Antacids
• H2 receptor antagonists
• Proton pump inhibitors
• Mucosal protectives
• Antibiotics

These are alkaline compounds that neutralize stomach acid, raising the gastric pH and thereby relieving pain . They are often given concurrently with acid-suppressing drugs such as H2 receptor antagonists and proton pump inhibitors in the treatment of peptic ulcers and reflux esophagitis. Most antacids contain aluminum hydroxide, magnesium hydroxide, sodium bicarbonate, or calcium carbonate . Other ingredients added to antacids include simethicone and alginic acid.

• Simethicone : Added to antacids to relieve flatulence and dyspepsia. It may be beneficial in relieving colic pain in infants. Common brands containing simethicone include Maalox Plus®, Alcid®, and Gestid®.
• Alginates : Added to antacids as protectants and are useful in the treatment of reflux esophagitis. Common brands containing alginate include Gaviscon®.
• Local anesthetics : Such as oxethazaine are added to antacids to reduce the pain associated with dyspepsia. Common brands containing oxethazaine include Mucogel® suspension and Mucaine® suspension.

Antacids containing sodium bicarbonate have a fast onset of action, but their absorption may worsen hypertension and heart failure.

Indications

Symptomatic relief of:

• Dyspepsia
• Gastroesophageal reflux disease
• Peptic ulcer disease
• Gastritis
• Heartburn

Contraindications

• Patients with severe abdominal pain of unknown cause
• Lactation
• Patients with cardiovascular problems (antacids with sodium)

Side Effects

• Magnesium-containing antacids tend to cause diarrhea, whereas aluminum-containing antacids may cause constipation and delay gastric emptying. A combination of the two may reduce the side effects of each.

Key Issues to Note

• Antacids should be taken between meals or at bedtime when symptoms are expected to occur.
• Optimum antacid effect is obtained if taken 1-3 hours after meals.
• Liquid antacids are generally more effective than tablets and have a rapid onset of action.
• Antacids are effective for a short period and should be given on a 6-hourly basis.
• Antacids may interact with numerous other drugs, affecting the rate and extent of their absorption. For example, tetracycline, ciprofloxacin, iron, indomethacin, and digoxin. A minimum interval of at least 2 hours should be left between the administration of antacids and other drugs.

ACICONE-S®

Available Preparations : Tablets, Suspension

Composition :

• Tablets: Magaldrate 720 mg, Simethicone 25 mg
• Suspension: Magaldrate 540 mg, Simethicone 40 mg

Indications :

• Heartburn in reflux esophagitis
• Prophylaxis against ulcer complications
• Adjunct to the treatment of peptic ulcers

Dosage :

• Tablets: 1 tablet to be chewed 4 times daily after meals or at bedtime
• Suspension: 5-10 ml 4 times daily after meals or at bedtime

AGOCID®

Available Preparations : Suspension

Composition : Dried aluminum gel 250 mg, Magnesium hydroxide 250 mg, Simethicone 50 mg

Indications :

• Acid dyspepsia
• Heartburn
• Pregnancy heartburn
• Adjunct to peptic ulcer treatment
• Reflux esophagitis

Dosage : 5-10 ml 4 times daily between meals

ALCID®

Available Preparations : Suspension

Composition : Aluminum hydroxide gel 400 mg, Magnesium hydroxide 400 mg, Simethicone 50 mg

Indications :

• Gastritis
• Flatulence
• Hiatus hernia
• Adjunct to the treatment of peptic ulcers
• Heartburn associated with reflux esophagitis
• Heartburn in pregnancy

Dosage : 5-10 ml 4 times a day between meals and at bedtime

CENTACID®

Available Preparations : Suspension

Composition : Aluminum hydroxide gel 250 mg, Magnesium hydroxide 200 mg, Simethicone 40 mg

Indications :

• Acid dyspepsia
• Reflux esophagitis
• Gastritis
• Pregnancy heartburn
• Hiatus hernia

Dosage : 5-10 ml 4 times a day between meals and at bedtime

RELCERGEL®

Available Preparations: Suspension

Composition : Aluminum hydroxide gel 6 g, Magnesium hydroxide 80 mg, Simethicone 100 mg, Deglycyrrhizinated liquorice 400 mg

Indications :

• Gastritis
• Flatulence
• Heartburn associated with reflux esophagitis
• Heartburn in pregnancy
• Adjunct to the treatment of peptic ulcers

Dosage : 5-10 ml 3-4 times daily after meals

Bismuth Subsalicylate

• Has cytoprotective properties and is bactericidal against H. pylori . It promotes healing of peptic ulcers by forming a complex (bismuth/glycoprotein) that coats the base of the peptic ulcer.
• It needs an acidic environment to work; hence, it should not be used in combination with antacids.

Available Preparations : Tablets (262 mg), Suspension

Available Brands : Pepto-Bismol®, Bismol®

Pharmacokinetics : Following oral administration, the drug is only slightly absorbed. Increased gastric pH may increase bismuth absorption. Unabsorbed drug is excreted in feces. The absorbed portion of the drug is distributed throughout body tissues and is slowly excreted in urine and bile.

Indications :

• Peptic ulcer
• Nausea
• Diarrhea
• Abdominal cramps
• Indigestion
• Prevention of traveler’s diarrhea

Contraindications :

• Hypersensitivity to bismuth salts
• Moderate to severe renal impairment
• Children under 3 years

Dosage :

Adults : 30 ml or 2 tablets 4 times daily, 30 minutes before food

Children :

• 9-12 years: 15 ml or 1 tablet 4 times daily
• 6-9 years: 10 ml 4 times daily
• 3-6 years: 5 ml 4 times daily

Side Effects :

• Black stool
• Discolors mucous membranes, tongue, and teeth
• Constipation
• Metallic taste
• Skin reactions
• Stomatitis

Drug Interactions :

• Bismuth subsalicylate decreases the absorption of tetracyclines.
• It increases the toxicity of aspirin due to the absorption of salicylate.

Key Issues to Note :

• Chew or dissolve tablets in the mouth before swallowing.
• Shake suspension before using.
• Stop use if symptoms do not improve within 2 days.

Misoprostol

Available Preparations : Tablets (200 mcg)

Available Brands : Cytotec®

Mode of Action : Misoprostol helps to protect the stomach by suppressing secretion of gastric acid, promoting secretion of bicarbonate and cytoprotective mucus, and maintaining blood flow.

Indications :

• Peptic ulcer disease
• Prophylaxis of NSAID-induced ulcers
• Induction of labor
• Management of postpartum hemorrhage

Contraindications :

• Pregnancy or those planning to become pregnant
• Women in childbearing age
• Breastfeeding
• Patients allergic to prostaglandin derivatives
• Inflammatory bowel disease

Dosage :

• By mouth: 800 mcg daily in 2-4 divided doses with food for 4-8 weeks
• Prophylaxis of NSAID-induced ulcers: 200 mcg 2-4 times daily taken with NSAID

Side Effects:

• Diarrhea
• Flatulence
• Abdominal cramps
• Dyspepsia
• Dizziness
• Nausea
• Vomiting
• Abnormal vaginal bleeding
• Rashes

Drug Interactions:

• Misoprostol diminishes the bioavailability of aspirin.
• Magnesium antacids enhance diarrhea associated with misoprostol.

H2 receptor antagonists reduce gastric acid secretion by blocking the action of histamine at the H2 receptor in the parietal cells of the stomach.

Examples:

• Cimetidine
• Famotidine
• Nizatidine
• Ranitidine

Ranitidine

Available Preparations : Tablets (150 mg, 300 mg), Injection (25 mg/ml, 2 ml)

Available Brands: Zantac®, Ranidenk®, Ranitin®, Rantac®, Aciloc®, R-Loc®

Pharmacokinetics : Ranitidine is readily absorbed from the gastrointestinal tract, widely distributed, metabolized in the liver, and excreted in urine.

Indications :

• Peptic ulcer
• Prophylaxis of NSAID-induced duodenal or gastric ulcer
• Stress ulcer prophylaxis
• Gastroesophageal reflux disease
• Zollinger-Ellison syndrome
• Dyspepsia

Contraindications :

• Patients allergic to ranitidine
• Children less than 8 years

Dosage :

Peptic ulcer :

• Adults and children over 12 years: 150 mg twice daily or 300 mg at night for 4 to 8 weeks

Prophylaxis of NSAID-induced duodenal or gastric ulcer : 150 mg twice daily

Gastroesophageal reflux disease : 150 mg twice daily or 300 mg at night up to 8 weeks; moderate to severe cases: 150 mg every 6 hours daily for up to 12 weeks

Zollinger-Ellison syndrome : 150 mg 3 times daily

Stress ulcer prophylaxis : 150 mg twice daily until the risk factor is removed

Dyspepsia : 150 mg twice daily for 4-8 weeks

• IV: 50 mg diluted to 20 ml with normal saline or dextrose 5% every 6-8 hours by slow injection over not less than 5 minutes
• IV Infusion: 25 mg/hour for 2 hours may be repeated every 6-8 hours

Side Effects:

• Skin rash
• Visual disturbance
• Gynecomastia
• Headache
• Diarrhea
• Malaise
• Tachycardia
• Constipation
• Hypersensitivity reaction
• Myalgia

Drug Interactions:

• Antacids may decrease the absorption of ranitidine.
• Ranitidine may decrease the absorption of ketoconazole, cefpodoxime, cefuroxime.
• Ranitidine may increase the hypoglycemic effects of glipizide.
• Ranitidine may interfere with warfarin clearance.

Proton pump inhibitors (PPIs) act by irreversibly binding to and inhibiting the enzyme H+/K+-ATPase (proton pump) of the gastric parietal cells, resulting in long-lasting but reversible acid suppression. PPIs inhibit gastric acid secretion more than H2 receptor antagonists.

Examples:

• Omeprazole
• Lansoprazole
• Pantoprazole
• Esomeprazole
• Rabeprazole

Omeprazole

Available Preparations : Enteric-coated capsules/tablets (20 mg)

Available Brands: Gasec®, Omepren®, Omizac®, Ocid®, Belifax®

Pharmacokinetics : Omeprazole is rapidly but variably absorbed after oral administration. Absorption is not affected by food. It is almost completely metabolized in the liver, and 80% of the metabolites are excreted mainly in urine and the rest in feces.

Indications :

• Peptic ulcers
• Zollinger-Ellison syndrome
• NSAID-associated duodenal or gastric ulcer
• Gastric acid reduction during anesthesia
• Gastroesophageal reflux disease
• Acid-related dyspepsia

Contraindications :

• Allergy to omeprazole or any other component in the capsule
• Pregnancy
• Lactation