Clinical Pharmacology for Nexium
Mechanism Of Action
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.
Pharmacodynamics
Antisecretory Activity The effect of esomeprazole on 24-hour intragastric pH in healthy subjects was evaluated in two studies of 20 mg and 40 mg NEXIUM I.V. infused intravenously once daily over 30 minutes for 5 days, as shown in Table 7.
Table 7: Effect of NEXIUM I.V. on Intragastric pH on Day 5
|
NEXIUM I.V.
20 mg once daily
(n=22) |
NEXIUM I.V.
40 mg once daily
(n=38) |
% Time Gastric pH>4
(95% CI) |
49.5
41.9 - 57.2 |
66.2
62.4 - 70.0 |
| Gastric pH was measured over a 24-hour period |
Gastric pH was measured over a 24-hour period
The effects of esomeprazole on 24-hour intragastric pH following administration of an intravenous infusion of 80 mg NEXIUM.I.V. over 30 minutes followed by a continuous infusion of 8 mg/hour for 23.5 hours was evaluated in two studies.
In H. pylori-negative healthy Caucasian subjects (n=24), the % time over 24 hours (95% CI) when the intragastric pH was > 6 and > 7 was 52.3 % (40.3, 64.4) and 4.8 % (1.8, 7.8), respectively.
In H. pylori-positive (n=8) and H. pylori-negative (n=11) healthy Chinese subjects, the % time over 24 hours (95% CI) when intragastric pH was > 6 and > 7 was 53% (45.6, 60.3) and 15.1% (9.5, 20.7). The percentage of time with intragastric pH > 6 [59% vs. 47%] and with pH > 7 [17% vs. 11%] tended to be larger in the H. pylori positive subjects compared to H. pylori-negative subjects.
Serum Gastrin Effects
The effect of esomeprazole on serum gastrin concentrations was evaluated in approximately 2,700 patients in clinical trials of oral esomeprazole for up to 8 weeks and in over 1,300 patients treated for up to 12 months. The mean fasting gastrin level increased in a dose-related manner. The increase in serum gastrin concentrations reached a plateau within two to three months of therapy and returned to baseline levels within four weeks after discontinuation of therapy.
Increased gastrin causes enterochromaffin-like cell hyperplasia and increased serum Chromogranin A (CgA) levels. The increased CgA levels may cause false positive results in diagnostic investigations for neuroendocrine tumors [see WARNINGS AND PRECAUTIONS].
Enterochromaffin-Like (ECL) Cell Effects
There are no data available on the effects of intravenous esomeprazole on ECL cells.
Human gastric biopsy specimens have been obtained from more than 3,000 patients (both children and adults) treated orally with omeprazole in long-term clinical trials. The incidence of ECL cell hyperplasia in these studies increased with time; however, no case of ECL cell carcinoids, dysplasia, or neoplasia has been found in these patients [see Nonclinical Toxicology].
In over 1,000 patients treated with oral esomeprazole (10 mg, 20 mg or 40 mg/day) for up to 12 months, the prevalence of ECL cell hyperplasia increased with time and dose. No patient developed ECL cell carcinoids, dysplasia, or neoplasia in the gastric mucosa.
Endocrine Effects
Esomeprazole had no effect on thyroid function when given in oral doses of 20 mg or 40 mg for 4 weeks. Other effects of esomeprazole on the endocrine system were assessed in studies of omeprazole. Oral doses of omeprazole 30 mg or 40 mg per day for 2 to 4 weeks had no effect on carbohydrate metabolism, circulating levels of parathyroid hormone, cortisol, estradiol, testosterone, prolactin, cholecystokinin or secretin.
Pharmacokinetics
Absorption
The pharmacokinetics of esomeprazole in healthy subjects following administration of NEXIUM I.V. 20 mg and 40 mg once daily as intravenous infusion over 30 minutes for 5 days are shown in Table 8.
Table 8: Geometric Mean (95% CI) Pharmacokinetic Parameters of NEXIUM I.V. Following Dosing for 5 Days
| Parameter |
NEXIUM I.V.
20 mg
(n=24) |
NEXIUM I.V.
40 mg
(n=38) |
AUC
(micromol*h/L) |
5.1
(4.0:6.6) |
16.2
(14.5:18.2) |
| Cmax (micromol/L) |
3.9
(3.2:4.7) |
7.5
(6.9:8.1) |
| t1/2 (h) |
1.1
(0.9:1.2) |
1.4
(1.3:1.5) |
Following intravenous administration of NEXIUM I.V. in 24 healthy subjects as a loading dose of 80 mg over 30 minutes followed by a continuous infusion of 8 mg/hour for 23.5 hours (for a total of 24 hours), esomeprazole pharmacokinetic parameters [geometric mean value (95% CI)] were as follows: AUCt 111.1 micromol*h/L (100.5, 122.7 micromol*h/L), Cmax 15.0 micromol/L (13.5, 16.6 micromol/L), and steady state plasma concentration (Css) 3.9 micromol/L (3.5, 4.5 micromol/L). In another study of healthy Caucasian subjects administered the same treatment regimen.
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.
Elimination
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
Esomeprazole is excreted as metabolites primarily in urine but also in feces. Less than 1% of parent drug is excreted in the urine. Esomeprazole is completely eliminated from plasma, and there is no accumulation during once daily administration. The plasma elimination half-life of esomeprazole following intravenous administration of NEXIUM I.V. is approximately 1.1 to 1.4 hours and is prolonged with increasing doses.
The plasma clearance (CL) is approximately 5.9 to 7.2 L/h during administration of NEXIUM I.V. as an intravenous infusion of 80 mg over 30 minutes followed by a continuous infusion of 8 mg/hour for 23.5 hours.
Specific Populations
Geriatric Patients
The AUC and Cmax values of esomeprazole were 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.
Pediatric Patients
The pharmacokinetics of esomeprazole were evaluated in 50 pediatric patients birth to 17 years of age, inclusive (of which 44 pediatric patients were 1 month to 17 years) in a randomized, open-label, multi-national, multiple dose study of 20 mg NEXIUM I.V. administered as a once-daily 3-minute intravenous injection. Esomeprazole plasma AUC values were 183% and 60% higher in pediatric patients aged 6 to 11 years and 12 to 17 years, respectively, compared to adults.
Subsequent pharmacokinetic analyses predicted the following dosage regimens would achieve comparable steady-state plasma exposures (AUC0-24) to those observed in adult patients administered 20 mg of NEXIUM I.V. once daily: 0.5 mg/kg once daily for pediatric patients 1 month to 11 months of age, 10 mg once daily for pediatric patients 1 year to 17 years with body weight less than 55 kg, and 20 mg once daily for pediatric patients 1 year to 17 years with body weight of 55 kg and greater. Increasing the infusion duration from 3 minutes to 10 minutes or 30 minutes was predicted to produce steady-state Cmax values that were comparable to those observed in adult patients at the 40 mg and 20 mg NEXIUM I.V. doses, respectively [see Use In Specific Populations].
Male And Female Patients
The AUC and Cmax values of esomeprazole were slightly higher (13%) in females than in males at steady state when dosed orally. Similar differences have been seen for intravenous administration of esomeprazole. This increase in exposure is not considered clinically relevant.
Patients With Renal Impairment
The pharmacokinetics of esomeprazole in patients with renal impairment are not expected to be altered relative to healthy subjects as less than 1% of esomeprazole is excreted unchanged in urine.
Patients With Hepatic Impairment
The steady state pharmacokinetics of esomeprazole obtained after administration of 40 mg orally once daily to 4 patients each with mild (Child-Pugh Class A), moderate (Child-Pugh Class B), and severe (Child-Pugh Class C) hepatic impairment were compared to those obtained in 36 male and female GERD patients with normal liver function. In patients with mild and moderate hepatic impairment, the AUCs were within the range that could be expected in patients with normal liver function. In patients with severe hepatic impairment, the AUCs were 2 to 3 times higher than in the patients with normal liver function. [see Use In Specific Populations].
There are no pharmacokinetic data available for esomeprazole administered as continuous intravenous administration in patients with liver impairment. The pharmacokinetics of intravenous omeprazole 80 mg infused over 30 minutes, followed by 8 mg/hour over 47.5 hours in patients with mild (Child-Pugh Class A; n=5), moderate (Child-Pugh Class B; n=4) and severe (Child-Pugh Class C; n=3) liver impairment were compared to those obtained in 24 male and female healthy subjects. In patients with mild and moderate liver impairment, omeprazole clearance and steady state plasma concentration was approximately 35% lower and 50% higher, respectively, than in healthy subjects. In patients with severe liver impairment, the omeprazole clearance was 50% of that in healthy subjects and the steady state plasma concentration was double that in healthy subjects [see Use In Specific Populations].
Drug Interaction Studies
Effect Of Esomeprazole/Omeprazole On Other Drugs
In vitro and in vivo studies have shown that esomeprazole is not likely to inhibit CYPs 1A2, 2A6, 2C9, 2D6, 2E1 and 3A4.
Antiretrovirals
For some antiretroviral drugs, such as rilpivirine, atazanavir and nelfinavir, decreased serum concentrations have been reported when given together with omeprazole [see DRUG INTERACTIONS].
Rilpivirine
Following multiple doses of rilpivirine (150 mg, daily) and omeprazole (20 mg, daily), AUC was decreased by 40%, Cmax by 40%, and Cmin by 33% for rilpivirine [see CONTRAINDICATIONS].
Nelfinavir
Following multiple doses of nelfinavir (1250 mg, twice daily) and omeprazole (40 mg daily), AUC was decreased by 36% and 92%, Cmax by 37% and 89% and Cmin by 39% and 75% respectively for nelfinavir and M8.
Atazanavir
Following multiple doses of atazanavir (400 mg, daily) and omeprazole (40 mg, daily, 2 hours before atazanavir), AUC was decreased by 94%, Cmax by 96%, and Cmin by 95%.
Saquinavir
Following multiple dosing of saquinavir/ritonavir (1000/100 mg) twice daily for 15 days with omeprazole 40 mg daily co-administered days 11 to 15. The AUC was increased by 82%, Cmax by 75%, and Cmin by 106%. The mechanism behind this interaction is not fully elucidated.
Clopidogrel
In a crossover study, healthy subjects were administered clopidogrel (300 mg loading dose followed by 75 mg per day as the maintenance dosage for 28 days) alone and with esomeprazole (40 mg orally once daily at the same time as clopidogrel) for 29 days. Exposure to the active metabolite of clopidogrel was reduced by 35% to 40% over this time period when clopidogrel and esomeprazole were administered together. Pharmacodynamic parameters were also measured and demonstrated that the change in inhibition of platelet aggregation was related to the change in the exposure to clopidogrel active metabolite [see WARNINGS AND PRECAUTIONS, DRUG INTERACTIONS].
Mycophenolate Mofetil
Administration of omeprazole 20 mg twice daily for 4 days and a single 1000 mg dose of MMF approximately one hour after the last dose of omeprazole to 12 healthy subjects in a cross-over study resulted in a 52% reduction in the Cmax and 23% reduction in the AUC of MPA [see DRUG INTERACTIONS].
Cilostazol
Omeprazole acts as an inhibitor of CYP2C19. Omeprazole, given in doses of 40 mg daily for one week to 20 healthy subjects in cross-over study, increased Cmax and AUC of cilostazol by 18% and 26% respectively. The Cmax and AUC of one of the active metabolites, 3,4-dihydro-cilostazol, which has 4-7 times the activity of cilostazol, were increased by 29% and 69%, respectively. Co-administration of cilostazol with omeprazole is expected to increase concentrations of cilostazol and the above mentioned active metabolite [see DRUG INTERACTIONS].
Diazepam
Co-administration of esomeprazole 30 mg and diazepam, a CYP2C19 substrate, resulted in a 45% decrease in clearance of diazepam. Increased plasma levels of diazepam were observed 12 hours after dosing and onwards. However, at that time, the plasma levels of diazepam were below the therapeutic interval, and thus this interaction is unlikely to be of clinical relevance.
Digoxin
Concomitant administration of omeprazole 20 mg once daily and digoxin in healthy subjects increased the bioavailability of digoxin by 10% (30% in two subjects) [see DRUG INTERACTIONS].
Other Drugs
Concomitant administration of esomeprazole and either naproxen (non-selective NSAID) did not identify any clinically relevant changes in the pharmacokinetic profiles of these NSAIDs.
Effect Of Other Drugs On Esomeprazole/Omeprazole
St. John’s Wort
In a cross-over study in 12 healthy male subjects, St. John’s Wort (300 mg three times daily for 14 days) significantly decreased the systemic exposure of omeprazole in CYP2C19 poor metabolizers (Cmax and AUC decreased by 37.5% and 37.9%, respectively) and extensive metabolizers (Cmax and AUC decreased by 49.6% and 43.9%, respectively) [see DRUG INTERACTIONS].
Voriconazole
Concomitant administration of omeprazole and voriconazole (a combined inhibitor of CYP2C19 and CYP3A4) resulted in more than doubling of the omeprazole exposure. When voriconazole (400 mg every 12 hours for one day, followed by 200 mg once daily for 6 days) was given with omeprazole (40 mg once daily for 7 days) to healthy subjects, the steady-state Cmax and AUC0-24 of omeprazole significantly increased: an average of 2 times (90% CI: 1.8, 2.6) and 4 times (90% CI:3.3, 4.4), respectively, as compared to when omeprazole was given without voriconazole [see DRUG INTERACTIONS].
Other Drugs
Co-administration of esomeprazole with oral contraceptives, diazepam, phenytoin, quinidine, naproxen (non-selective NSAID) did not seem to change the pharmacokinetic profile of esomeprazole.
Microbiology
Effects On Gastrointestinal Microbial Ecology
Decreased gastric acidity due to any means including proton pump inhibitors, increases gastric counts of bacteria normally present in the gastrointestinal tract. Treatment with proton pump inhibitors may lead to slightly increased risk of gastrointestinal infections such as Salmonella and Campylobacter and, in hospitalized patients, possibly also Clostridium difficile.
Pharmacogenomics
CYP2C19, a polymorphic enzyme, is involved in the metabolism of esomeprazole. The CYP2C19*1 allele is fully functional while the CYP2C19*2 and *3 alleles are nonfunctional. There are other alleles associated with no or reduced enzymatic function. Patients carrying two fully functional alleles are extensive metabolizers and those carrying two loss-of-function alleles are poor metabolizers. The systemic exposure to esomeprazole varies with a patient’s metabolism status: poor metabolizers > intermediate metabolizers > extensive metabolizers. Approximately 3% of Caucasians and 15 to 20% of Asians are CYP2C19 poor metabolizers.
Systemic esomeprazole exposures were modestly higher (approximately 17%) in CYP2C19 intermediate metabolizers (IM; n=6) compared to extensive metabolizers (EM; n=17) of CYP2C19. Similar pharmacokinetic differences were noted across these genotypes in a study of Chinese healthy subjects that included 7 EMs and 11 IMs. There is very limited pharmacokinetic information for poor metabolizers (PM) from these studies.
At steady state following once daily administration of NEXIUM I.V. 40 mg, the ratio of AUC in Poor Metabolizers to AUC in the rest of the population (EMs) is approximately 1.5. This change in exposure is not considered clinically meaningful.
Animal Toxicology And/Or Pharmacology
Reproduction Studies
Reproduction studies have been performed in rats at oral doses up to 280 mg/kg/day (about 68 times an oral human dose of 40 mg on a body surface area basis) and in rabbits at oral doses up to 86 mg/kg/day (about 42 times an oral human dose of 40 mg on a body surface area basis) and have revealed no evidence of impaired fertility or harm to the fetus due to esomeprazole [see Use In Specific Populations].
Juvenile Animal Study
A 28-day toxicity study with a 14-day recovery phase was conducted in juvenile rats with esomeprazole magnesium at doses of 70 to 280 mg/kg/day (about 17 to 68 times a daily oral human dose of 40 mg on a body surface area basis). An increase in the number of deaths at the high dose of 280 mg/kg/day was observed when juvenile rats were administered esomeprazole magnesium from postnatal day 7 through postnatal day 35. In addition, doses equal to or greater than 140 mg/kg/day (about 34 times a daily oral human dose of 40 mg on a body surface area basis), produced treatment-related decreases in body weight (approximately 14%) and body weight gain, decreases in femur weight and femur length, and affected overall growth. Comparable findings described above have also been observed in this study with another esomeprazole salt, esomeprazole strontium, at equimolar doses of esomeprazole.
Clinical Studies
Acid Suppression In GERD
Four multicenter, open-label, two-period crossover studies were conducted to compare the pharmacodynamic effects of esomeprazole following intravenous or oral administration on acid suppression in 206 patients with symptoms of GERD with or without erosive esophagitis. Patients were randomized to receive either 20 or 40 mg of NEXIUM I.V. or oral esomeprazole once daily for 10 days (Period 1), and then were switched in Period 2 to the other formulation for 10 days, matching their respective dose from Period 1. NEXIUM I.V. 20 mg and 40 mg was administered as a 3-minute injection in two of the studies and as a 15-minute infusion in the other two studies.
The patient population ranged from 18 to 72 years old; 54% were female; 53% Caucasian, 24% Black, 5% Asian, and 17% other race. Basal acid output (BAO) and maximal acid output (MAO) were determined 22 to 24 hours post-dose on Period 1, Day 11; on Period 2, Day 3; and on Period 2, Day 11. BAO and MAO were estimated from 1-hour continuous collections of gastric contents prior to and following (respectively) subcutaneous injection of 6.0 mcg/kg of pentagastrin.
In these studies, after 10 days of once daily administration, NEXIUM I.V. 20 mg and 40 mg were similar to the corresponding oral dosage of esomeprazole in their ability to suppress BAO and MAO in these GERD patients (see Table 9 below).
There were no major changes in acid suppression when switching between intravenous and oral dosage forms.
Table 9: Mean (SD) BAO and MAO Measured 22 to 24 Hours Post-Dose Following Once Daily Oral and Intravenous Administration of Esomeprazole for 10 days in GERD Patients with or without a History of EE
|
BAO in mmol H+/h |
MAO in mmol H+/h |
| Study |
Dose in mg |
Intravenous Administration Method |
Intravenous |
Oral |
Intravenous |
Oral |
| 1 (N=42) |
20 |
3-minute injection |
0.71 (1.24) |
0.69 (1.24) |
5.96 (5.41) |
5.27 (5.39) |
| 2 (N=44) |
20 |
15-minute infusion |
0.78 (1.38) |
0.82 (1.34) |
5.95 (4.00) |
5.26 (4.12) |
| 3 (N=50) |
40 |
3-minute injection |
0.36 (0.61) |
0.31 (0.55) |
5.06 (3.90) |
4.41 (3.11) |
| 4 (N=47) |
40 |
15-minute infusion |
0.36 (0.79) |
0.22 (0.39) |
4.74 (3.65) |
3.52 (2.86) |
Bleeding Gastric Or Duodenal Ulcers
A randomized, double blind, placebo-controlled clinical study was conducted in 764 patients who presented with endoscopically confirmed gastric or duodenal ulcer bleeding. The population was 18 to 98 years old; 68% were male, 87% Caucasian, 1% Black, 7% Asian, and 4% other race. Following endoscopic hemostasis, patients were randomized to either placebo or NEXIUM I.V. 80 mg as an intravenous infusion over 30 minutes followed by a continuous infusion of 8 mg/hour for a total of 72 hours. After the initial 72-hour period, all patients received an oral PPI for 27 days. The occurrence of rebleeding within 3 days of randomization was 5.9% in the NEXIUM I.V. treated group compared to 10.3% for the placebo group (treatment difference -4.4%; 95% confidence interval: -8.3%, -0.6%; p=0.03). This treatment difference was similar to that observed at Day 7 and Day 30, during which all patients were receiving an oral PPI.
A randomized, double blind, placebo-controlled single-center study conducted in Hong Kong also demonstrated a reduction compared to placebo in the risk of rebleeding within 72 hours in patients with bleeding gastric or duodenal ulcers who received racemic omeprazole, 50% of which is the S-enantiomer esomeprazole.