The study is to compare the rate and extent of absorption of a generic formulation with that of a reference for mulation when given as equal labeled dose. The study will be randomized, open-label, single dose, full replicate crossover design with four-period, two-treatment, and two-sequence under fed condition and at least 7 days washout period between the doses.

Title A Bioequivalence study of a randomized, open-label, single dose, full replicate crossover design with four-period, two-treatment, and two-sequence of Esomeprazole magnesium dihydrate 40 mg tablets relative to Nexium 40 mg tablets in healthy Thai volunteers under fed condition.

Objectives The primary objective is to compare the rate and extent of absorption of a generic formulation with that of a reference formulation when given as equal labeled dose. The secondary objective is to evaluate the safety after oral administration of both test and reference formulation in healthy Thai volunteers.

Study Design Randomized, open-label, single dose, full replicate crossover design with four-period, two-treatment, and two-sequence under fed condition and at least 7 days washout period between the doses.

Sample Size 40 Healthy Human Thai subjects. Four extra subjects if available, may be checked-in on the day of check in of period-I to compensate for any dropout prior to dosing of period-I. These subjects will be dosed if there are dropouts prior to dosing in period-I. If there are no dropouts, these subjects will be checked-out without being dosed after completion of dosing in period-I.

Drug-Product Test-Product: Esomeprazole 40 mg gastro-resistant tablets Reference-product: Nexium® 40 mg tablets Manufactured by: AstraZeneca AB, Kingdom of Sweden

Administration After an overnight fasting at clinical facility of at least 10 hours prior to high fat high calorie breakfast, each volunteer will receive a single dose of Esomeprazole 40 mg gastro-resistant tablets of either test or reference with 250 mL of drinking water after starting high fat high calorie breakfast. Each volunteer will be allowed to drink water as desire except 1 hour before and after drug administration. The formulation is given in a crossover fashion as per the randomization schedule. After the administration, the subject's oral cavity will be checked by using flashlight to confirm complete medication and fluid consumption by pharmacist.

Blood Schedule In each period, a total of 21 blood samples (approximately 5 mL each) will be collected pre-dose (0.00 hour) and at 0.50, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 8.00, 9.00, 10.00, 12.00, 16.00 and 24.00 hours after study drug administration, respectively.

Sample Collection Blood samples will be collected through an indwelling catheter placed in a vein using disposable syringe or through fresh venipuncture with disposable syringes and needles. Approximately 5 mL blood sample will be withdrawn and transferred to sample collection pre-labeled tubes containing K3EDTA as anticoagulant at each sampling time point. Invert collection tube 3-5 times immediately after collection. After collection, all samples transfer into centrifugation room at controlled temperature (2-8 °C). Samples will be centrifuged at 4000 rpm for 5 minutes at 4±2°C. After centrifugation, the plasma samples will be aliquoted into two pre-labeled cryovials for approximately 1 mL in original cryovial and leaving the remaining volume for the duplicate cryovial. The plasma will be added in the pre-added buffer of 0.5M Sodium hydrogen carbonate in Milli-Q water to the pre-labeled cryovials, proper adjustments for buffer addition which will be permissible but the final composition of buffer in plasma will be 5% of total volume. The cryovials will be then vortexed for 30 seconds on multitube vortexer. Cryovials containing plasma sample will be stored at -70±10 °C.

Analytical Method Esomeprazole plasma concentration will be assayed as per international Guidelines/In-house SOP by using a UPLC-MS/MS method.

Pharmacokinetic Parameters Primary pharmacokinetic parameter: Cmax, AUC0→t and AUC0→∞ and secondary pharmacokinetic parameter: Tmax, T1/2, Kel, AUC0→t/AUC0→∞ will be determined from the plasma concentration data of analytes.

Statistical Analysis ANOVA, two one-sided tests for bioequivalence, for log-transformed pharmacokinetic parameters Cmax, AUC0→t and AUC0→∞ will be performed.

Acceptance Criteria for Bioequivalence To be considered as bioequivalent,

1. The 90% CI of AUC0→t and AUC0→∞ of Esomeprazole of test and reference products of the log-transformed data should be between 80.00-125.00%.
2. The 90% CI of Cmax of Esomeprazole of test and reference products of the log-transformed data should be in the acceptance criteria based on the within-subject variability seen in the study using scaled-average-bioequivalence as recommended in the 2010 EMA guideline

Inclusion Criteria:

1. Willingness to provide written informed consent prior to participate in the study.
2. Healthy Thai subjects are between 18 to 55 years of age.
3. The Body Mass Index (BMI) ranges from 18.5 to 30 kg/m2.
4. Comprehensive of the nature and purpose of the study and compliance with the requirement of the entire protocol and allow investigators to draw 7 mL of blood for monitoring subjects' safety after the completion of the study.
5. Negative urine pregnancy test for women and no breast-feeding.
6. Absence of significant diseases or clinically significant abnormal laboratory values on the laboratory evaluations, medical history or surgery during the screening. Some of the laboratory values e.g. Complete blood count etc. that out of the normal range will be carefully considered by physician.

Exclusion Criteria:

1. History or evidence of allergy or hypersensitivity to Esomeprazole, substituted benzimidazoles e.g. Omeprazole, Lansoprazole, Dexlansoprazole, Pantoprazole, Albendazole, Mebendazole or any of the excipients of this product.
2. Subject with B.P. is Systolic B.P < 90, ≥ 140 mm/Hg, Diastolic B.P < 60, ≥ 90 mm/Hg or pulse rate > 100 beats per minute.
3. Serum bilirubin greater than 1.5 times the upper limit of reference range (ULRR).*
4. Serum creatinine greater than 1.5 times the upper limit of reference range (ULRR).*
5. Alanine amino transferase (ALT) or aspartate amino transferase (AST) greater than 2 times the upper limit of reference range (ULRR).*
6. Positive of hepatitis B or C virus or HIV.
7. Have more than one abnormal EKG, which is considered as clinically significant. *
8. History or evidence of heart (unstable angina pectoris, myocardial infarction, cardiovascular), stroke, renal, hepatic disease, pulmonary obstructive disease, bronchial asthma, diabetes mellitus with vascular disease, gout disease, hypertension or glaucoma.
9. History or evidence of gastrointestinal disorder likely to influence drug absorption or previous GI surgery other than appendectomy.
10. Any major illness in the past 3 months or any significant ongoing chronic medical illness.
11. History of psychiatric disorder.
12. History of regular alcohol consumption exceeding 7 drinks/week for females or 14 drinks/week for males (1 drink = 5 ounces (150 mL) of wine or 12 ounces (360 mL) of beer or 1.5 ounces (45 mL) of hard liquor) and cannot stop at least 2 days before the study drug administration and until the completion of each period of the study.
13. History of usually smoking (more than 10 cigarettes per day within past 1 year), if moderate smokers (less than 10 cigarettes per day) cannot stop at least 7 days before the study drug administration and until the completion of the study.
14. High caffeine consumption (more than 5 cups of coffee or tea per day) and cannot stop at least 2 days before the study drug administration and until the completion of each period of the study.
15. History of grapefruit, pomelo or grapefruit products consumption and cannot stop at least 7 days before the study drug administration and until the completion of the study.
16. History of St. John's Wort or St. John's Wort product consumption and cannot stop at least 7 days before the study drug administration and until the completion of the study.
17. Positive drug abused test in urine (Benzodiazepines, Marijuana (THC), Methamphetamine, Cocaine and Opioids).
18. Receipt of any prescription drug therapy within 14 days or 5 half-lives (whichever longer) preceding the first dose of study medication or over-the-counter (OTC) drugs or herbal medicines/food supplement within 7 days or hormonal methods of contraception within 28 days (Depo-Provera must be discontinued at least 6 months) prior to receiving the first dose of study medication.
19. History of difficulty in accessibility of veins in left and right arm.
20. Blood donation (one unit or 450 mL) within the past 3 months before the study.
21. Participation in any clinical study within the past 3 months before the study.
22. Subjects who are unwilling or unable to comply with the lifestyle guidelines described in this protocol.

(* Depend on decision of principal investigator and/or clinical investigator)

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