Calcium Hasco (o smaku pomarańczowym)

Pharmacodynamics. Mechanism of action. Pantoprazole is a substituted benzimidazole that inhibits gastric hydrochloric acid secretion by specifically blocking the proton pumps of parietal cells. Pantoprazole is converted to its active form in the acidic environment of parietal cells, where it inhibits the H⁺/K⁺-ATPase enzyme, thereby blocking the final step of hydrochloric acid production in the stomach. This inhibition is dose-dependent and affects both basal and stimulated acid secretion. Most patients become symptom-free within 2 weeks. Treatment with pantoprazole, as with other proton pump inhibitors (PPIs) and H2-receptor antagonists, reduces gastric acidity and thereby increases gastrin secretion in proportion to the reduction in acidity. The increase in gastrin secretion is reversible. Since pantoprazole binds to the enzyme distal to the cell receptor, it can inhibit hydrochloric acid secretion regardless of stimulation by other substances (acetylcholine, histamine, gastrin). The effect is the same whether the drug is administered orally or intravenously. Fasting gastrin levels increase during pantoprazole treatment. With short-term use, they generally do not exceed the upper limit of normal. During long-term treatment, gastrin levels double in most cases. Excessive increases occur only in isolated cases. As a result, in a small number of cases during long-term treatment, a mild to moderate increase in specific endocrine (ECL) cells in the stomach is observed (similar to adenomatoid hyperplasia). However, according to studies conducted to date, the formation of neuroendocrine tumour precursor cells (atypical hyperplasia) or gastric neuroendocrine tumours, which were found in animal studies, has not been observed in humans. Based on the results of animal studies, an effect of long-term (more than one year) pantoprazole treatment on thyroid endocrine parameters cannot be excluded. During treatment with antisecretory medicinal products, serum gastrin levels rise in response to decreased acid secretion. In addition, chromogranin A (CgA) levels increase due to decreased gastric acidity. Elevated CgA levels may interfere with investigations for neuroendocrine tumours. Available published data suggest that PPI therapy should be discontinued between 5 days and 2 weeks prior to CgA measurements. This allows CgA levels to return to the normal range, which may be falsely elevated after PPI treatment. Pharmacokinetics. Absorption. Pantoprazole is rapidly absorbed, and peak plasma concentrations are achieved after a single oral dose of 40 mg. The peak serum concentration of approximately 2–3 µg/mL is reached on average 2.5 hours after administration; concentrations remain constant after repeated dosing. Pharmacokinetic properties do not change after single or repeated administration. In the dose range of 10 to 80 mg, plasma pharmacokinetics of pantoprazole are linear after both oral and intravenous administration. The absolute bioavailability of the tablets is approximately 77%. Concomitant food intake does not affect AUC (area under the concentration-time curve) or peak serum concentration and, consequently, bioavailability. Only the variability of the lag time increases with concomitant food intake. Distribution. Pantoprazole serum protein binding is approximately 98%. The volume of distribution is approximately 0.15 L/kg. Biotransformation. The substance is metabolised almost exclusively in the liver. The main metabolic pathway is demethylation by CYP2C19 followed by sulphate conjugation; other metabolic pathways include oxidation by CYP3A4. Elimination. The terminal half-life is approximately 1 hour, and clearance is 0.1 L/h/kg. There have been a few cases of delayed elimination. Due to the specific binding of pantoprazole to the proton pumps of parietal cells, the half-life does not correlate with the considerably longer duration of action (acid secretion inhibition). The majority of pantoprazole metabolites are excreted renally (approximately 80%); the remainder is excreted in faeces. The main metabolite in both serum and urine is desmethylpantoprazole conjugated with sulphate. The half-life of the main metabolite (approximately 1.5 hours) is not much longer than that of pantoprazole. Special patient populations. Slow metabolisers. Approximately 3% of Europeans lack functional CYP2C19 enzyme activity and are referred to as slow metabolisers. In these individuals, pantoprazole metabolism is probably mainly catalysed by CYP3A4. After a single dose of 40 mg pantoprazole, the mean area under the plasma concentration-time curve was approximately 6 times greater in slow metabolisers than in individuals with functionally active CYP2C19 (extensive metabolisers). The mean peak plasma concentration increased by approximately 60%. These findings do not affect the dosage recommendations for pantoprazole. Renal impairment. No dose reduction is recommended when prescribing pantoprazole to patients with impaired renal function (including patients on dialysis). As in healthy individuals, the half-life of pantoprazole is short. Only very small amounts of pantoprazole are dialysed. Although the main metabolite has a moderately prolonged half-life (2–3 hours), elimination is still rapid, and therefore accumulation does not occur. Hepatic impairment. Although the half-life increases to 7–9 hours and the AUC increases 5- to 7-fold in patients with hepatic cirrhosis (Child-Pugh classes A and B), the peak serum concentration increases only slightly — by 1.5-fold compared with healthy volunteers. Elderly patients. The slight increase in AUC and Cmax in elderly volunteers compared with younger volunteers is also of no clinical significance.