Introduction
Pantoprazole is a first-generation proton pump inhibitor (PPI) used for the management of gastroesophageal reflux disease (GERD), for gastric protection to prevent recurrence of stomach ulcers or gastric damage from chronic use of NSAIDs, and for the treatment of pathological hypersecretory conditions including Zollinger-Ellison (ZE) Syndrome. It can also be found in quadruple regimens for the treatment of H. pylori infections along with other antibiotics including amoxicillin, clarithromycin, and metronidazole, for example. Its efficacy is considered similar to other medications within the PPI class including omeprazole, esomeprazole, lansoprazole, dexlansoprazole, and rabeprazole.
Pantoprazole exerts its stomach acid-suppressing effects by preventing the final step in gastric acid production by covalently binding to sulfhydryl groups of cysteines found on the (H+, K+)-ATPase enzyme at the secretory surface of gastric parietal cell. This effect leads to inhibition of both basal and stimulated gastric acid secretion, irrespective of the stimulus. As the binding of pantoprazole to the (H+, K+)-ATPase enzyme is irreversible and new enzyme needs to be expressed in order to resume acid secretion, pantoprazole's duration of antisecretory effect persists longer than 24 hours.
Due to their good safety profile and as several PPIs are available over the counter without a prescription, their current use in North America is widespread. Long term use of PPIs such as pantoprazole have been associated with possible adverse effects, however, including increased susceptibility to bacterial infections (including gastrointestinal C. difficile), reduced absorption of micronutrients including iron and B12, and an increased risk of developing hypomagnesemia and hypocalcemia which may contribute to osteoporosis and bone fractures later in life.
PPIs such as pantoprazole have also been shown to inhibit the activity of dimethylarginine dimethylaminohydrolase (DDAH), an enzyme necessary for cardiovascular health. DDAH inhibition causes a consequent accumulation of the nitric oxide synthase inhibitor asymmetric dimethylarginie (ADMA), which is thought to cause the association of PPIs with increased risk of cardiovascular events in patients with unstable coronary syndromes.
Pantoprazole doses should be slowly lowered, or tapered, before discontinuing as rapid discontinuation of PPIs such as pantoprazole may cause a rebound effect and a short term increase in hypersecretion.
Uses
Pantoprazole is a proton pump inhibitor used to treat erosive esophagitis, gastric acid hypersecretion, and to promote healing of tissue damage caused by gastric acid.
Pantoprazole Injection:
Treatment of gastroesophageal reflux disease associated with a history of erosive esophagitis
Pantoprazole for injection is indicated for short-term treatment (7-10 days) of patients having gastroesophageal reflux disease (GERD) with a history of erosive esophagitis, as an alternative to oral medication in patients who are unable to continue taking pantoprazole delayed-release tablets. Safety and efficacy of pantoprazole injection as the initial treatment of patients having GERD with a history of erosive esophagitis have not been demonstrated at this time.
Pathological Hypersecretion Associated with Zollinger-Ellison Syndrome
Pantoprazole for injection is indicated for the treatment of pathological hypersecretory conditions associated with Zollinger-Ellison Syndrome or other neoplastic conditions.
Pantoprazole delayed-release oral suspension:
Short-Term Treatment of erosive esophagitis associated with gastroesophageal reflux disease (GERD)
Indicated in adults and pediatric patients five years of age and above for the short-term treatment (up to 8 weeks) in the healing and symptomatic relief of erosive esophagitis. For adult patients who have not healed after 8 weeks of treatment, an additional 8-week course of pantoprazole may be considered. Safety of treatment beyond 8 weeks in pediatric patients has not been determined.
Maintenance of healing of erosive esophagitis
Indicated for maintenance of healing of erosive esophagitis and reduction in relapse rates of daytime and nighttime heartburn symptoms in adult patients with GERD.
Pathological hypersecretory conditions including Zollinger-Ellison syndrome
Indicated for the long-term treatment of the above conditions.
Associated Conditions
Pharmacodynamics
This drug acts to decrease gastric acid secretion, which reduces stomach acidity. Pantoprazole administration leads to long-lasting inhibition of gastric acid secretion.
General Effects
Pantoprazole has been shown to reduce acid reflux-related symptoms, heal inflammation of the esophagus, and improve patient quality of life more effectively than histamine-2 receptor antagonists (H2 blockers). This drug has an excellent safety profile and a low incidence of drug interactions. It can be used safely in various high-risk patient populations, including the elderly and those with renal failure or moderate hepatic dysfunction.
Due to their good safety profile and as several PPIs are available over the counter without a prescription, their current use in North America is widespread. Long term use of PPIs such as pantoprazole have been associated with possible adverse effects, however, including increased susceptibility to bacterial infections (including gastrointestinal C. difficile), reduced absorption of micronutrients including iron and B12, and an increased risk of developing hypomagnesemia and hypocalcemia which may contribute to osteoporosis and bone fractures later in life.
PPIs such as pantoprazole have also been shown to inhibit the activity of dimethylarginine dimethylaminohydrolase (DDAH), an enzyme necessary for cardiovascular health. DDAH inhibition causes a consequent accumulation of the nitric oxide synthase inhibitor asymmetric dimethylarginie (ADMA), which is thought to cause the association of PPIs with increased risk of cardiovascular events in patients with unstable coronary syndromes .
A note on laboratory testing abnormalities
During treatment with antisecretory medicinal products such as pantoprazole, serum gastrin (a peptide hormone that stimulates secretion of gastric acid) increases in response to the decreased acid secretion caused by proton pump inhibition. The increased gastrin level may interfere with investigations for neuroendocrine tumors. Published evidence suggests that proton pump inhibitors should be stopped 14 days before chromogranin A (CgA) measurements. This permits chromogranin A levels, that might be falsely elevated after proton pump inhibitor treatment, to return to the normal reference range.
Reports have been made of false-positive results in urine screening tests for tetrahydrocannabinol (THC) in patients receiving the majority of proton pump inhibitors, including pantoprazole. A confirmatory method should be used.
Mechanism of Action
Hydrochloric acid (HCl) secretion into the gastric lumen is a process regulated mainly by the H(+)/K(+)-ATPase of the proton pump, expressed in high quantities by the parietal cells of the stomach. ATPase is an enzyme on the parietal cell membrane that facilitates hydrogen and potassium exchange through the cell, which normally results in the extrusion of potassium and formation of HCl (gastric acid).
Proton pump inhibitors such as pantoprazole are substituted benzimidazole derivatives, weak bases, which accumulate in the acidic space of the parietal cell before being converted in the canaliculi (small canal) of the gastric parietal cell, an acidic environment, to active sulfenamide derivatives. This active form then makes disulfide bonds with important cysteines on the gastric acid pump, inhibiting its function. Specifically, pantoprazole binds to the sulfhydryl group of H+, K+-ATPase, which is an enzyme implicated in accelerating the final step in the acid secretion pathway. The enzyme is inactivated, inhibiting gastric acid secretion. The inhibition of gastric acid secretion is stronger with proton pump inhibitors such as pantoprazole and lasts longer than with the H(2) antagonists.
Absorption
Pantoprazole is absorbed after oral administration as an enteric-coated tablet with maximum plasma concentrations attained within 2 – 3 hours and a bioavailability of 77% that does not change with multiple dosing . Following an oral dose of 40mg, the Cmax is approximately 2.5 μg/mL with a tmax of 2 to 3 hours. The AUC is approximately 5 μg.h/mL. There is no food effect on AUC (bioavailability) and Cmax.
Delayed-release tablets are prepared as enteric-coated tablets so that absorption of pantoprazole begins only after the tablet leaves the stomach.
Volume of Distribution
The apparent volume of distribution of pantoprazole is approximately 11.0-23.6 L, distributing mainly in the extracellular fluid.
Protein Binding
Approximately 98%
Route of Elimination
After a single oral or intravenous (IV) dose of 14C-labeled pantoprazole to healthy, normal metabolizing subjects, about 71% of the dose was excreted in the urine, with 18% excreted in the feces by biliary excretion. There was no kidney excretion of unchanged pantoprazole.
Half Life
About 1 hour
Clearance
Adults: With intravenous administration of pantoprazole to extensive metabolizers, total clearance is 7.6-14.0 L/h. In a population pharmacokinetic analysis, the total clearance increased with increasing body weight in a non-linear fashion.
Children: clearance values in the children 1 to 5 years old with endoscopically proven GERD had a median value of 2.4 L/h.
Toxicity
Rat Oral LD 50 747 mg/kg
Tumorigenicity
Because of the chronic nature of GERD, there may be a potential for long-term administration of pantoprazole. In long-term rodent studies, pantoprazole was carcinogenic and its administration lead to rare types of gastrointestinal tumors. The relevance of these findings to tumor development in humans is unknown at this time.
Teratogenic Effects
This drug falls under pregnancy category B category. Reproduction studies have been performed in rats at oral doses up to 88 times the recommended human dose (RHD), as well as in rabbits at oral doses up to 16 times the RHD, and have shown no evidence of impaired fertility or harm to the fetus caused by pantoprazole. No adequate and well-controlled studies in pregnant women have been completed. Because animal reproduction studies are not always predictive of human response, this drug should only be used during pregnancy if clearly required.
Nursing Mothers
Pantoprazole and its metabolites have been found to be excreted in the milk of rats. Pantoprazole excretion in human milk has been found in a study performed with a single nursing mother after one 40 mg oral dose. The clinical relevance of this finding is not known, however, it is advisable to take note of this finding when considering pantoprazole use during nursing. Many drugs excreted in human breastmilk have a risk for serious adverse effects in nursing infants.
Food Interactions
- Take with or without food. The absorption is unaffected by food.
