pantoprazole

Proton pump inhibitor· Brands: Protonix, Pantoloc, Somac, Protium, EupantolIVPO

Mechanism of action

Pantoprazole is a substituted benzimidazole that irreversibly inhibits the gastric hydrogen-potassium ATPase (proton pump) in the secretory canaliculi of parietal cells. It is activated by acid, forming a covalent bond with cysteine residues on the enzyme, thereby blocking the final step of gastric acid secretion. This results in profound and long-lasting suppression of both basal and stimulated acid production.

Pharmacokinetics

Pantoprazole is absorbed after oral administration with an absolute bioavailability of approximately 77%. Peak plasma concentrations occur 2-3 hours after dosing. It is extensively metabolised in the liver via CYP2C19 (and CYP3A4 to a minor extent) to inactive metabolites. The elimination half-life is about 1-2 hours, but the antisecretory effect persists longer due to irreversible enzyme binding. Excretion is predominantly renal (about 80% as metabolites), with the remainder in faeces.

Indications & dosing

Gastro-oesophageal reflux disease (GORD)

Usual course 4-8 weeks; maintenance may be reduced to 20 mg.

adult · PO: 40 mg once daily · Usual course 4-8 weeks; maintenance may be reduced to 20 mg.

Peptic ulcer disease

For 4-8 weeks; if H. pylori positive, combine with eradication therapy.

adult · PO: 40 mg once daily · For 4-8 weeks; if H. pylori positive, combine with eradication therapy.

Helicobacter pylori eradication (in combination)

Used with antibiotics (e.g. amoxicillin, clarithromycin, metronidazole) for 7-14 days.

adult · PO: 40 mg twice daily · Used with antibiotics (e.g. amoxicillin, clarithromycin, metronidazole) for 7-14 days.

Zollinger-Ellison syndrome

Dose adjusted according to response; higher doses may be required.

adult · PO: 40–80 mg once daily · Dose adjusted according to response; higher doses may be required.

Contraindications & precautions

Hypersensitivity to pantoprazole or other substituted benzimidazoles · Cross-reactivity among substituted benzimidazoles is possible.
Concurrent use with atazanavir · Pantoprazole increases gastric pH and reduces atazanavir absorption, decreasing antiviral efficacy.
Exclude malignancy in gastric ulcer before starting treatment.
In severe hepatic impairment, do not exceed a daily dose of 40 mg.
Long-term use (over 1 year) may cause hypomagnesemia, vitamin B12 deficiency, osteoporosis-related fractures, and fundic gland polyps; review need for continued therapy periodically.
Coadministration with methotrexate, especially high doses, may increase methotrexate levels; monitor for methotrexate toxicity.
Coadministration with warfarin may enhance anticoagulant effect; monitor INR.
Use with caution in pregnancy and breastfeeding; limited data available.

Adverse effects

Headache
Diarrhoea
Nausea
Abdominal pain
Flatulence
Dizziness
Anaphylaxisserious
Angioedemaserious
Hypomagnesemiaserious
Severe cutaneous adverse reactions (e.g., SJS/TEN)serious

Renal & hepatic adjustment

Hepatic impairment (severe): Consider dose reduction to 20 mg daily in severe hepatic impairment; monitor for adverse effects.

Monitoring, pregnancy & toxicity

Serum magnesium · Before and periodically during long-term treatment, especially with concurrent drugs that cause hypomagnesemia.
Vitamin B12 levels · Consider in long-term treatment.
Symptom relief and healing · Assess response.
Pregnancy: Pantoprazole is considered safe in pregnancy; use the lowest effective dose for the shortest duration.
Toxicity: Overdose may cause headache, nausea, vomiting, diarrhoea, dizziness. · Supportive care; no specific antidote. Consider activated charcoal within an hour if significant ingestion.

Clinical notes

Pantoprazole is indicated for gastro-oesophageal reflux disease, peptic ulcer disease, and as part of Helicobacter pylori eradication therapy. It is available as oral and intravenous formulations. Common adverse effects include headache, gastrointestinal disturbances (diarrhoea, constipation, flatulence), and nausea. Long-term use may be associated with hypomagnesaemia, vitamin B12 deficiency, and an increased risk of fractures. It can interact with drugs requiring an acidic gastric environment (e.g., ketoconazole, atazanavir) or those metabolised by CYP2C19 (e.g., clopidogrel, though the clinical significance is debated).

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BNF; local formulary