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Pharmacology: Pharmacodynamics: Pantoprazole is metabolized in the liver by the cytochrome P450 system. Metabolism mainly consists of demethylation by CYP2C19 followed by sulfation. Another metabolic pathway is oxidation by CYP3A4. Pantoprazole metabolites are not thought to have any pharmacological significance. Pantoprazole is relatively free of drug interactions; however, it may alter the absorption of other medications that depend on the amount of acid in the stomach, such as ketoconazole or digoxin.
Generally inactive at acidic pH of stomach, thus it is usually given with a prokinetic drug. Pantoprazole binds irreversibly to H+K+ATpase (proton pumps) and suppresses the secretion of acid. As it binds irreversibly to the pumps, new pumps have to be made before acid production could be resumed. The drug's plasma half-life is about 2 hours.
Domperidone blocks the action of dopamine. It has strong affinities for the D2 and D3 dopamine receptors, which are found in the chemoreceptor trigger zone, located just outside the blood brain barrier, which among others, and regulates nausea and vomiting (area postrema on the floor of the fourth ventricle and rhomboid fossa).
Pharmacokinetics: Pantoprazole: Pantoprazole is unstable in acid and is administered orally in form of enteric-coated tablet. Absorption takes place in the small intestine. On average, the maximum serum/plasma concentrations are approximately 2 to 3 micrograms/mL about 2½ hrs after administration of 40 mg pantoprazole daily.
Domperidone: In man, peak plasma level of domperidone occurs within 30 minutes after oral (fasted) administration. Peak plasma concentrations are 20 mg/mL after a single 10 mg tablet, and 70 to 100 mg/mL after oral doses of 60 mg. After administration of 40 mg 4-domperidone to healthy volunteers, 31% of the radioactivity is excreted in the urine and 66% in the feces over a period of 4 days.
