Pariet® (Rabeprazole)

Disclaimer: This information is for educational purposes and is not a substitute for professional medical advice. Always consult your doctor before starting or stopping any medication. Do not self-diagnose or self-medicate based on this information.

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Pariet® (Rabeprazole): The Definitive Guide to a Leading PPI

Manufacturer: Marketed by Janssen-Cilag and imported/distributed in Egypt by SOFICOPHARM.

Category: Proton Pump Inhibitor (PPI), Substituted Benzimidazole

Active Ingredient: Rabeprazole Sodium (10 mg or 20 mg)

Available Form: Enteric-coated (gastro-resistant) tablets.

Summary

Pariet® (Rabeprazole) is a highly effective medication belonging to the Proton Pump Inhibitor (PPI) class, used to treat conditions caused by excess stomach acid. It works by directly shutting down the "pumps" in the stomach lining that produce acid, providing powerful and long-lasting relief from symptoms and helping to heal acid-related damage to the esophagus and stomach.

Pharmacodynamic Properties: How Pariet® Works

Mechanism of Action

Pariet® specifically targets and inhibits the H+/K+-ATPase enzyme system, also known as the "proton pump," located in the parietal cells of the stomach wall. This is the final step in the production of gastric acid. By blocking this pump, Rabeprazole effectively reduces both basal and stimulated acid secretion, regardless of the stimulus (e.g., food, hormones).

As a weak base, Rabeprazole is absorbed and concentrates in the acidic environment of the parietal cells. There, it is converted into its active sulfenamide form, which then binds to the proton pump, deactivating it. The tablets are enteric-coated, which means they have a special layer to protect the Rabeprazole from being destroyed by the stomach acid itself, allowing it to be absorbed in the intestine.

Anti-secretory Activity

The effect starts within an hour of taking a 20 mg dose, reaches its maximum in 2-4 hours, and can last for up to 48 hours. After the first dose, it inhibits basal and food-stimulated acid secretion by 69% and 82% respectively. When the drug is stopped, secretory activity typically returns to normal within 2-3 days.

Effect on Serum Gastrin

During the first 2-8 weeks of treatment, serum gastrin levels may increase, reflecting the drug's inhibitory effect on acid. These levels typically remain stable with continued treatment and return to pre-treatment levels 1-2 weeks after discontinuation. This is a normal and expected physiological response.

Therapeutic Indications: When is Pariet® Used?

Pariet® is indicated for the treatment of several acid-related disorders:

• Active Duodenal Ulcer & Active Benign Gastric Ulcer: For healing ulcers in the intestine and stomach.
• Gastro-Oesophageal Reflux Disease (GORD/GERD):
  • For healing erosive or ulcerative damage to the esophagus caused by acid reflux.
  • For long-term management and maintenance to prevent relapse.
  • For treating the symptoms of GORD (like heartburn) even without esophageal damage.
• Eradication of Helicobacter pylori: As part of a combination therapy with two antibiotics (e.g., clarithromycin and amoxicillin) to eliminate the H. pylori bacteria, which is a major cause of peptic ulcers and gastritis. Rabeprazole has also shown a bactericidal effect on H. pylori in vitro.

Dosage and Administration

Dosage depends on the condition being treated. Tablets should be swallowed whole and not be chewed or crushed.

• Duodenal/Gastric Ulcer & Erosive GORD: Typically 20 mg once daily in the morning for 4-8 weeks.
• GORD Maintenance: 10 mg or 20 mg once daily, depending on patient response.
• Symptomatic GORD: 10 mg once daily as needed ("on-demand" therapy) after initial symptoms are controlled.
• H. pylori Eradication: 20 mg of Pariet® taken twice daily for 7 days, in combination with two prescribed antibiotics.

Pharmacokinetic Properties: How the Body Handles Pariet®

• Absorption: Absorption begins only after the tablet leaves the stomach. It is rapid, with peak plasma levels occurring approximately 3.5 hours after a 20 mg dose. Bioavailability is about 52% and is not significantly affected by food.
• Distribution: Rabeprazole is approximately 97% bound to human plasma proteins.
• Metabolism: It is extensively metabolized in the liver by cytochrome P450 enzymes (CYP2C19 and CYP3A4).
• Excretion: No unchanged drug is excreted in the urine. Approximately 90% of the dose is eliminated in the urine as two main metabolites. The remainder is recovered in feces. The plasma half-life is approximately one hour.
• Special Populations: Elimination is somewhat decreased in the elderly. In patients with severe hepatic dysfunction, the half-life is significantly prolonged, and dosage adjustment with caution is advised. No dosage adjustment is typically needed for patients with renal impairment.

Adverse Effects

Pariet® is generally well-tolerated. Most side effects are mild to moderate and transient.

• Common (≥5% incidence): Headache, diarrhea, nausea.
• Less Common (1-5% incidence): Rhinitis, abdominal pain, asthenia (weakness), flatulence, pharyngitis, vomiting, back pain, dizziness, cough, constipation, and insomnia.
• Rare (Post-marketing reports):
  • Allergic Reactions: Severe systemic reactions like facial swelling, hypotension (low blood pressure), and dyspnea (difficulty breathing) have been reported, which usually resolve after stopping treatment.
  • Blood Disorders: Thrombocytopenia (low platelets), neutropenia (low neutrophils), and leucopenia (low white blood cells).
  • Liver Effects: Increased liver enzymes, and rarely, hepatitis and jaundice. In patients with underlying cirrhosis, rare reports of hepatic encephalopathy exist.
  • Skin Reactions: Erythema, and very rarely, severe reactions like Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).
  • Other: Very rare reports of interstitial nephritis (kidney inflammation) and gynecomastia (enlargement of breast tissue in males).

Key Contraindications, Warnings, and Drug Interactions

• Contraindications: Known hypersensitivity to Rabeprazole or other PPIs. It is also contraindicated during pregnancy and breastfeeding.
• Malignancy: Symptomatic relief with Pariet® does not rule out the presence of a stomach malignancy. This must be excluded by a doctor before starting long-term treatment.
• Drug Interactions: Pariet® can affect the absorption of drugs that depend on stomach pH. It can decrease the levels of antifungals like ketoconazole and increase the levels of digoxin. It does not appear to have clinically significant interactions with warfarin, phenytoin, or theophylline.
• Driving/Operating Machinery: While unlikely to cause impairment, if you experience somnolence (drowsiness), it is recommended to avoid driving or operating complex machinery.

Overdose Information

Experience with overdose is limited. The effects are generally minimal and similar to the known side effect profile. There is no specific antidote, and because Rabeprazole is highly protein-bound, it is not easily removed by dialysis. Treatment is symptomatic and supportive.

Sources

1. Rabeprazole Professional Information - Drugs.com
2. Rabeprazole - StatPearls, NCBI
3. Official Product Leaflet for Pariet®.