Esomeprazole 40 mg, Itopride 150 mg (SR) Hard-gelatin capsules

Esomeprazole belongs to a class of antisecretory compounds, the substituted benzimidazoles, that suppress gastric acid secretion by specific inhibition of the H+/K+ ATPase enzyme system at the secretory surface of the gastric parietal cell. Esomeprazole is protonated and converted in the acidic compartment of the parietal cell forming the active inhibitor, the achiral sulphenamide. Because this enzyme system is regarded as the acid (proton) pump within the gastric mucosa, esomeprazole has been characterized as a gastric acid-pump inhibitor, in that it blocks the final step of acid production.

This effect is dose-related and leads to inhibition of both basal and stimulated acid secretion irrespective of the stimulus.

Absorption — Esomeprazole magnesium delayed-release capsules showed similar bioavailability after a single dose (40 mg) administration in 94 healthy male and female subjects under fasting conditions. After oral administration, peak plasma levels (Cmax) of esomeprazole occur at approximately 1.5 hours (Tmax). The Cmax increases proportionally when the dose is increased, and there is a three-fold increase in the area under the plasma concentration-time curve (AUC) from 20 to 40 mg. At repeated once-daily dosing with 40 mg, the systemic bioavailability is approximately 90% compared to 64% after a single dose of 40 mg. The mean exposure (AUC) to esomeprazole increases from 4.32 micromol *hr/L on Day 1 to 11.2 micromol *hr/L on Day 5 after 40 mg once daily dosing.

The AUC after administration of a single 40 mg dose of esomeprazole magnesium delayed-release capsules is decreased by 43% to 53% after food intake compared to fasting conditions esomeprazole magnesium [see Dosage and Administration (2.3)]. The pharmacokinetics of esomeprazole in adult patients with symptomatic GERD following repeated once daily administration of 20 mg and 40 mg esomeprazole magnesium delayed-release capsules over a period of five days are shown in Table 6:

1. Values represent the geometric mean, except the Tmax, which is the arithmetic mean; CV = Coefficient of variation

Esomeprazole is a time-dependent inhibitor of CYP2C19, resulting in autoinhibition and nonlinear pharmacokinetics. The systemic exposure increases in a more than dose proportional manner after multiple oral doses of esomeprazole.

Compared to the first dose, the systemic exposure (Cmax and AUC0-24h) at steady state following once a day dosing increased by 43% and 90%, respectively, compared to after the first dose for the 20 mg dose and increased by 95% and 159%, respectively, for the 40 mg dose.

Distribution — Esomeprazole is 97% bound to plasma proteins. Plasma protein binding is constant over the concentration range of 2 to 20 micromol /L. The apparent volume of distribution at steady state in healthy subjects is approximately 16 L.

Metabolism — Esomeprazole is extensively metabolized in the liver by the cytochrome P450 (CYP) enzyme system. The metabolites of esomeprazole lack antisecretory activity. The major part of esomeprazole’s metabolism is dependent upon the CYP2C19 isoenzyme, which forms the hydroxy and desmethyl metabolites. The remaining amount is dependent on CYP3A4 which forms the sulphone metabolite.

Excretion — The plasma elimination half-life of esomeprazole is approximately 1 to 1.5 hours. Less than 1% of parent drug is excreted in the urine. Approximately 80% of an oral dose of esomeprazole is excreted as inactive metabolites in the urine, and the remainder is found as inactive metabolites in the feces.

Combination Therapy with Amoxicillin and Clarithromycin — Esomeprazole magnesium delayed-release capsules 40 mg once daily was given in combination with amoxicillin 1000 mg twice daily and clarithromycin 500 mg twice daily for 7 days to 17 healthy male and female subjects. The mean steady state AUC and Cmax of esomeprazole increased by 70% and 18%, respectively during combination therapy compared to treatment with esomeprazole magnesium alone. The observed increase in esomeprazole exposure during co-administration with amoxicillin and clarithromycin is not expected to be clinically relevant.

The pharmacokinetic parameters for amoxicillin and clarithromycin were similar during combination therapy and administration of each drug alone. However, the mean AUC and Cmax for 14-hydroxyclarithromycin increased by 19% and 22%, respectively, during combination therapy compared to treatment with clarithromycin alone. This increase in exposure to 14-hydroxyclarithromycin is not considered to be clinically relevant.

Geriatric Patients — The AUC and Cmax values were of esomeprazole slightly higher (25% and 18%, respectively) in the elderly as compared to younger subjects at steady state. This increase in exposure is not considered clinically relevant.

Itopride combines dopamine D2 receptor antagonism with acetylcholinesterase inhibition. Increased acetylcholine activity supports gastric motility and gastric emptying.

The immediate-release reference describes rapid gastrointestinal absorption, approximately 60% relative bioavailability and a peak 0.5–0.75 hours after 50 mg. Plasma protein binding is about 96%. Hepatic FMO3 metabolism forms an N-oxide; urinary recovery after the cited dose was 3.7% unchanged drug and 75.4% N-oxide. Terminal half-life is approximately 6 hours. Animal tissue-distribution findings are not human measurements, and these data do not establish sustained-release kinetics.