High-performance liquid chromatographic determination of lansoprazole and its metabolites in human serum and urine

Utility of the 13 C-pantoprazole breath test as a CYP2C19 phenotyping probe for children

The ¹³ C-pantoprazole breath test (PAN-BT) is a safe, non-invasive, in-vivo CYP2C19 phenotyping probe for adults. Our objective was to evaluate PAN-BT performance in children, with a focus on discriminating individuals who, according to guidelines from the Clinical Pharmacology Implementation Consortium (CPIC), would benefit from starting dose escalation vs. reduction for proton pump inhibitors (PPIs). Children (n=65; 6-17 years) genotyped for CYP2C19 variants *2, *3, *4, and *17 received a single oral dose of ¹³ C-pantoprazole. Plasma concentrations of pantoprazole and its metabolites, and changes in exhaled ¹³ CO₂ (termed delta-over-baseline or DOB), were measured 10 times over 8 hours using HPLC-UV and spectrophotometry, respectively. Pharmacokinetic parameters of interest were generated and DOB features derived using feature engineering for the first 180 minutes post-administration. DOB features, age, sex, and obesity status were used to run bootstrap analysis at each timepoint (T_i)  independently. For each iteration, stratified samples were drawn based on genotype prevalence in the original cohort. A random forest was trained, and predictive performance of PAN-BT evaluated. Strong discriminating ability for CYP2C19 intermediate vs. normal/rapid metabolizer phenotype was noted at DOB_T30min (mean sensitivity: 0.522, specificity: 0.784), with consistent model outperformance over a random or a stratified classifier approach at each time-point (p<0.001). With additional refinement and investigation, the test could become a useful and convenient dosing tool in clinic to help identify children who would benefit most from PPI dose escalation vs. dose reduction, in accordance with CPIC guidelines.

Qualitative and quantitative determination of anaprazole and its major metabolites in human plasma

Anaprazole is a novel proton pump inhibitor under development for the treatment of gastric and duodenal ulcers. In the present study, an ultra-performance liquid chromatography-ultraviolet detector/quadrupole time-of-flight mass spectrometry method was developed for the metabolic profiling of human plasma after an oral administration of 40 mg anaprazole. The principal metabolic pathways were identified as sulfoxide reduction to thioether (M8-1), dehydrogenation (M21-1), sulfoxide oxidation to sulfone (M16-3), and sulfoxide reduction with O-demethylation to form carboxylic acid (M7-1). Anaprazole, M8-1, M16-3, M21-1, and M7-1 were selected and further quantified in human plasma by using a rapid and sensitive liquid chromatography-tandem mass spectrometry method. Anaprazole and its four metabolites were extracted from 50 of μL plasma by acetonitrile protein precipitation. Chromatographic retention and separation were achieved on an Kinetex XB-C₁₈ column (50 mm × 4.6 mm i.d., 5 μm) under gradient elution using 5 mM ammonium acetate with 0.005 % ammonium hydroxide and methanol with 0.005 % ammonium hydroxide as the mobile phase. Positive electrospray ionization was performed using multiple reaction monitoring with transitions of m/z 402.2→242.2, 386.2→226.2, 400.2→242.2, 418.2→282.2, and 386.2→161.2 for anaprazole, M8-1, M21-1, M16-3, and M7-1, respectively. This method was linear in the range of 5.00-3000 ng/mL for anaprazole and 1.00-600 ng/mL for the four metabolites. The lower limit of quantitation was established at 5.00 ng/mL for anaprazole and 1.00 ng/mL for the metabolites. The quantitative method was used to evaluate the pharmacokinetics of anaprazole in phase I clinical trials.

Lean body weight dosing avoids excessive systemic exposure to proton pump inhibitors for children with obesity

BACKGROUND

Children with obesity are more likely to suffer gastroesophageal reflux disease, requiring acid-suppression therapy with proton pump inhibitors (PPIs) and no guidelines regarding dosing.

OBJECTIVE

To prospectively evaluate lean-body-weight-based (LBW) dosing of the PPI pantoprazole for children with and without obesity.

METHODS

Methods: Sixty-two children (6-17 years) received a one-time oral dose of liquid pantoprazole (1.2 mg kg^-1 LBW). Plasma pantoprazole concentrations were measured at 10 time points over 8 h and pharmacokinetic (PK) profiles generated using non-compartmental techniques, in order to compare PK parameters of interest between children with and without obesity, while accounting for CYP2C19 genotype.

RESULTS

Adjusted for milligram-per-kilogram total body weight (TBW) pantoprazole received, apparent drug clearance (CL/F) was reduced 50% in children with vs. without obesity (p=0.03). LBW-based dosing compensated for this reduction in CL/F (p = 0.15).

CONCLUSION

To achieve comparable systemic PPI exposures for children with and without obesity, we recommend using LBW, rather than TBW-based dosing for pantoprazole.

Proton pump inhibitors reduce interferon-γ-induced neurotoxicity and STAT3 phosphorylation of human astrocytes

Proton pump inhibitors (PPIs) are known to possess anti-inflammatory properties. Inflammatory processes, including astrocytic activation, are implicated in the pathogenesis of different neurodegenerative diseases. Our recent study has indicated that interferon (IFN)-γ-induced astrocytic neurotoxicity is mediated, at least in part, by phosphorylation of signal transducer and activator of transcription (STAT) 3. We therefore studied the effects of PPIs on IFN-γ-induced neurotoxicity and STAT3 activation of human astrocytes. Both lansoprazole (LPZ) and omeprazole (OPZ) significantly attenuated IFN-γ-induced neurotoxicity of human astrocytes and astrocytoma cells. These drugs inhibited IFN-γ-induced phosphorylation of STAT 3, but not STAT1. We found that LPZ significantly reduced secretion of IFN-γ-inducible T cell α chemoattractant from IFN-γ-activated astrocytes. Neither LPZ nor OPZ suppressed expression of intercellular adhesion molecule-1 by IFN-γ-activated astrocytes. These results suggest that PPIs attenuate IFN-γ-induced neurotoxicity of human astrocytes through inhibition of the STAT3 signaling pathway. PPIs that possess antineurotoxic properties may be a useful treatment option for Alzheimer's disease and other neuroinflammatory disorders associated with activated astrocytes.

Simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone in human plasma by LC-MS/MS: application to a pharmacokinetic study in healthy volunteers

A highly sensitive and specific liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone. The detection was operated with multiple reaction-monitoring (MRM) using the electrospray ionization technique. The assay procedure involved precipitation of plasma samples with acetonitrile after indapamide was added as internal standard (IS). The chromatographic separation was achieved with a mixture of methanol-0.2% ammonium acetate and 0.1% methanoic acid in water (75:25, v/v) as mobile phase on an Inertsil ODS-3 column. The method was proved to be accurate and precise with linearity ranges of 10-4,000 ng/ml, 5.0-400 ng/ml, and 1.0-400 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively, with the correlation coefficients (r) better than 0.999. The lower limits of quantification (LLOQ) were 2.0 ng/ml, 2.0 ng/ml, and 0.5 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits (R.S.D.% within +/-15) in accordance with FDA guidelines. The validated LC-MS/MS method has been successfully applied for the determination of lansoprazole and its metabolites in human plasma.

Comparison of the enteral and intravenous lansoprazole pharmacodynamic responses in critically ill patients

BACKGROUND

While proton pump inhibitors are frequently administered in the intensive care unit, the pharmacodynamic response of acid suppression between the enteral and intravenous (IV) route is unknown.

AIM

To compare the pharmacodynamic response between enteral and IV lansoprazole in intensive care unit patients requiring stress ulcer prophylaxis therapy.

METHODS

Adult mechanically ventilated patients were randomized to receive 72 h of daily enteral [lansoprazole oral disintegrating tablet (LODT) 30 mg mixed in 10 mL of water via a nasal gastric tube] or IV lansoprazole (30 mg over 30 min) therapy. Serial blood samples were collected after the first and third dose and analysed for pharmacokinetic parameters. Pharmacodynamic determination of intragastric pHmetry began prior to the first dose and continued for 72 h using a single channel pH microelectrode.

RESULTS

Nineteen intensive care unit patients were randomized [LODT (n = 10); IV-L (n = 9)]. LODT bioavailability was 76%. LODT maintained gastric pH > 4 longer than IV-L at both 24 h (7.4 vs. 5.9 h; P = 0.039) and 72 h (10.4 and 8.9 h; P = 0.046) and resulted in a greater average pH over the first 24 h (3.67 vs. 2.89; P = 0.03).

CONCLUSION

Despite a lower bioavailability, enteral lansoprazole suppresses acid in intensive care unit patients to a greater extent than IV lansoprazole.

An in vitro comparison of different providers to deliver four proton pump inhibitor products through a feeding tube

BACKGROUND

It is unclear how delivery through a feeding tube compares between esomeprazole in water, lansoprazole oral disintegrating tablet in water, omeprazole/NaHCO(3) in water and simplified lansoprazole suspension.

AIM

This in vitro study compared delivery through a narrow calibre (8F) feeding tube among four proton pump inhibitors when given by skilled [nurse; (n = 8)] or unskilled [lay; (n = 8)] providers.

METHODS

Following standard instruction, subjects were observed delivering each proton pump inhibitor in a sequential, but random, fashion to evaluate administration quality and time. Delivery was quantified using high-performance liquid chromatography methods and subject preferences were evaluated.

RESULTS

Delivery (%), similar between lansoprazole oral disintegrating tablet (95.7 +/- 3.2) and omeprazole/NaHCO(3) (96.1 +/- 3.0), was both greater for lansoprazole oral disintegrating tablet than esomeprazole in water (88.9 +/- 8.6; P = 0.006) or simplified lansoprazole suspension (86.1 +/- 9.5; P = 0.0001) and omeprazole/NaHCO(3) than esomeprazole in water (P = 0.004) or simplified lansoprazole suspension (P < 0.001), and was not affected by prior subject experience. Quality was higher with both omeprazole/NaHCO(3) and lansoprazole oral disintegrating tablet than simplified lansoprazole suspension. Administration was quicker for lansoprazole oral disintegrating tablet than esomeprazole in water. Subjects preferred lansoprazole oral disintegrating tablet and omeprazole/NaHCO(3).

CONCLUSIONS

When given through an in vitro feeding tube, omeprazole/NaHCO(3) and lansoprazole oral disintegrating tablet lead to greater drug delivery, improved administration quality and higher user satisfaction, than either esomeprazole in water or simplified lansoprazole suspension.

Beyond gastric acid reduction: Proton pump inhibitors induce heme oxygenase-1 in gastric and endothelial cells

Proton pump inhibitors (PPIs) have been demonstrated to prevent gastric mucosal injury by mechanisms independent of acid inhibition. Here we demonstrate that both omeprazole and lansoprazole protect human gastric epithelial and endothelial cells against oxidative stress. This effect was abrogated in the presence of the heme oxygenase-1 (HO-1) inhibitor ZnBG. Exposure to either PPI resulted in a strong induction of HO-1 expression on mRNA and protein level, and led to an increased activity of this enzyme. Expression of cyclooxygenase isoforms 1 and 2 remained unaffected, and COX-inhibitors did not antagonize HO-1 induction by PPIs. Our results suggest that the antioxidant defense protein HO-1 is a target of PPIs in both endothelial and gastric epithelial cells. HO-1 induction might account for the gastroprotective effects of PPIs independently of acid inhibition, especially in NSAID gastropathy. Moreover, our findings provide additional perspectives for a possible but yet unexplored use of PPIs in vasoprotection.

Effect of water intake on pharmacokinetics of lansoprazole from fast disintegrating tablet in human subjects

Lansoprazole fast disintegrating tablet (LFDT) has been developed as a multiple unit formulation to increase the QOL of patients, i.e., easy intake without water. However, there is a possibility that patients intake LFDT in accordance with clarithromycin and amoxicillin with water. To study the effect of water on the absorption of lansoprazole (LPZ), the study was carried out using human volunteers. After selected by phenotype of LPZ metabolism, extensive metabolizers (EMs) of LPZ were used in this study. Twelve healthy male EMs intook LFDT containing 30 mg LPZ with 150 mL of water and without-water, i.e., with saliva, to study the pharmacokinetics of LPZ from the gastrointestinal tract by a cross-over manner with one-week washout period under fasted condition in the morning. The mean AUC(0-24s) were 2004.4+/-973.6 ng.h/mL in without-water experiment and 2018.5+/-1159.6 ng.h/mL in the case of with-water experiment. Mean C(maxs) were 851.9+/-450.8 ng/mL in without-water experiment and 830.8+/-456.8 ng/mL in with-water experiment, respectively. ANOVA was applied to the log-transformed AUC(0-24) and C(max) values. The 90% two sided confidence intervals for log-transformed AUC(0-24) was 0.78-1.22 and that for log-transformed C(max) was 0.67-1.37, respectively. By comparing these pharmacokinetic parameters, we may state that there was no significant difference between the two administration modes.

Determination of lansoprazole and two of its metabolites by liquid–liquid extraction and automated column-switching high-performance liquid chromatography: application to measuring CYP2C19 activity

A simple and sensitive column-switching high-performance liquid chromatographic (HPLC) method for the simultaneous determination of lansoprazole, a proton pump inhibitor and its major metabolites: 5-hydroxylansoprazole and lansoprazole sulfone in human plasma. The test compounds were extracted from 1 mL of plasma using diethyl ether-dichloromethane (7:3, v/v) mixture and the extract was injected into a column I (TSK-PW precolumn, 10 microm, 3.5 mm x 4.6 mm i.d.) for clean-up and column I (C(18) STR ODS-II analytical column, 5 microm, 150 mm x 4.6 mm i.d.) for separation. The peak was detected by a ultraviolet detector set at a wavelength of 285 nm, and the total time for a chromatographic separation was approximately 25 min. The method was validated for the concentration range from 3 to 5000 ng/mL. Mean recoveries were 74.0% for lansoprazole, 68.3% for 5-hydroxylansoprazole, and 79.4% for lansoprazole sulfone. Intra- and inter-day relative standard derivatives were less than 6.1 and 5.1% for lansoprazole, 5.8 and 5.8% for 5-hydroxylansoprazole, 4.4 and 5.9% for lansoprazole sulfone, respectively, at the different concentration ranges. This method is suitable for use in therapeutic drug monitoring and pharmacokinetic studies, and provides use tool for measuring CYP2C19 activity.

Effect of adsorbents on the absorption of lansoprazole with surfactant

Lansoprazole (LPZ) is a representative drug that shows a high inter-subject variation of bioavailability (BA). Solid preparation composed of surfactant, adsorbent and LPZ were prepared to improve the dissolution and absorption of LPZ, and the BA of LPZ was measured in rats and dogs. As surfactant, Tween 80, polyoxy 60 hydrogenated caster oil derivative (HCO-60) and PEG-8 caprylic/capric glycerides (Labrasol) were used. As adsorbant, porous silicon dioxide (Sylysia 550, 320), magnesium aluminometa silicate (Neusilin S2, NS2N, US2) and porous calcium silicate (Florite RE) were used. After small intestinal administration of LPZ, 5.0 mg/kg, solution with HCO-60 showed the highest plasma LPZ concentration versus time curve of which C(max) and AUC was 0.46+/-0.01 microg/mL and 0.73+/-0.03 microgh/mL. By comparing to that after i.v. injection of LPZ solution, 2.0 mg/kg, the BA of LPZ from HCO-60 solution was 39.0%, which was about seven times higher than that of LPZ powder. To solidify the LPZ solution with HCO-60, adsorbents were used and the obtained solid preparations were used for in vitro release experiment. Sylysia 320, Neusilin S2 and Neusilin NS2 showed the T50% of about 1h. To evaluate the BA of these solid preparations, absorption study was performed in rats. Sylysia 550 system showed the higher AUC than other systems, showing the BA of 28.1%. Sylysia 550 system was filled in an enteric capsule and was orally administered to dogs and BA was compared with enteric tablet. The AUC of Sylysia 550 system was 2.16+/-0.26 microgh/mL and was greater than enteric tablet and the BA of 71.7% was obtained. Solid system composed of LPZ, surfactant and adsorbent has suggested the possibility as a good tool to improve the BA of LPZ.

Evaluation of Fast Disintegrating Lansoprazole Tablet in Human Subjects

Fast disintegrating lansoprazole tablet (LFDT) has been developed as a multiple unit formulation and evaluated using human subjects as compared to the conventional lansoprazole (LPZ) capsule containing enteric coated granules. Twelve healthy male volunteers, who were confirmed as extensive metabolizers (EMs) based on the plasma levels of LPZ sulphone metabolite, were enrolled into the study and genotype of CYP2C19 was confirmed. They kept 30 mg LFDT in their mouths for 2 min and the saliva was recovered without swallow. Eight subjects did not show LPZ in their serum after intake. Although LPZ was detected in 4 subjects' serum, their concentrations were less than 5 ng/mL. LPZ was thought to be not absorbed from the oral cavity. LFDT was orally administered to 12 healthy male EMs at two doses, 15 mg and 30 mg, and serum LPZ concentrations were measured. The mean C(max) and AUC(0-24) were 474.1+/-254.0 ng/mL and 1105.3+/-1101.4 ng.h/mL (15 mg) and 992.8+/-384.3 ng/mL and 2216.5+/-1270.1 ng.h/mL (30 mg). By comparing to that obtained after oral administration of the same doses of LPZ capsule, serum LPZ concentration vs. time curve was almost the same level, i.e., C(max) and AUC(0-24) did not have significant differences. From these results, LFDT has been shown to be equivalent to LPZ capsule and will show the same acid suppressing effects in the clinical situation.

Lansoprazole quantification in human plasma by liquid chromatography-electrospray tandem mass spectrometry

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection was developed for the determination of lansoprazole in human plasma using omeprazole as the internal standard. The analyte and internal standard were extracted from the plasma samples by liquid-liquid extraction using diethyl-ether-dichloromethane (70:30; v/v) and chromatographed on a C(18) analytical column. The mobile phase consisted of acetonitrile-water (90:10; v/v)+10 mM formic acid. The method has a chromatographic total run time of 5 min and was linear within the range 2.5-2000 ng/ml. Detection was carried out on a Micromass triple quadrupole tandem mass spectrometer by Multiple Reaction Monitoring (MRM). The intra- and inter-run precision, calculated from quality control (QC) samples, was less than 3.4%. The accuracy as determined from QC samples was less than 9%. The method herein described was employed in a bioequivalence study of two capsule formulations of lansoprazole.

Comparison of lansoprazole and famotidine for gastric acid inhibition during the daytime and night-time in different CYP2C19 genotype groups

BACKGROUND

The acid inhibitory effect of lansoprazole depends on the S-mephenytoin 4'-hydroxylase (CYP2C19) genotype status. The effect of famotidine is independent of this genotype.

AIM

To investigate the acid inhibitory effects of lansoprazole vs. famotidine during the daytime and night-time with reference to different CYP2C19 genotypes.

METHODS

Fifteen healthy volunteers were given 20 mg famotidine twice a day or 30 mg lansoprazole once a day for 8 days. On post-dose day 8, 24-h intragastric pH monitoring was performed.

RESULTS

During the daytime, the intragastric pH with lansoprazole was significantly higher than that with famotidine in the heterozygous extensive metabolizer group, whereas no significant difference was observed in the homozygous extensive metabolizer group. During the night-time, the intragastric pH with famotidine was quite similar to that with lansoprazole in the heterozygous extensive metabolizer and poor metabolizer groups. However, during the night-time, the intragastric pH with famotidine was significantly higher than that with lansoprazole in the homozygous extensive metabolizer group.

CONCLUSIONS

An insufficient acid inhibition by lansoprazole during the night-time in the homozygous extensive metabolizer group could be compensated for by famotidine. CYP2C19 genotype testing appears to be useful for predicting the optimal acid inhibitory drug treatment collated with circadian intragastric pH change.

Influence of fluconazole on the pharmacokinetics of omeprazole in healthy volunteers

Influence of fluconazole on the pharmacokinetics of omeprazole was evaluated by single oral administration of omeprazole capsule 20 mg (control group), or single oral administration of fluconazole capsule, 100 mg, and omeprazole, 20 mg, after 4 days of daily oral administration of fluconazole, 100 mg (treated group), to 18 healthy male volunteers. Omeprazole is extensively metabolized in the liver through 5-hydroxylation and sulfoxidation reactions catalyzed predominantly by CYP2C19 and CYP3A4, respectively. Fluconazole is a potent competitive inhibitor of CYP2C19 and a weak inhibitor of CYP3A4. In treated group, the area under the plasma concentration-time curve of omeprazole from time zero to time infinity (AUC) was significantly greater (3090 vs 491 ng h/ml), terminal half-life of omeprazole was significantly longer (2.59 vs 0.85 h), and peak plasma concentration of omeprazole (C(max)) was significantly higher (746 vs 311 ng/ml) than that in control group. The greater AUC and higher C(max) in treated group could be due to inhibition of omeprazole metabolism by fluconazole.

Omeprazole pharmacodynamics and gastric acid suppression in critically ill pediatric transplant patients

OBJECTIVE: To characterize the pharmacodynamics and pharmacokinetics of omeprazole suspension in critically ill pediatric liver/intestinal transplant patients. DESIGN: Open-label pharmacodynamic and pharmacokinetic study. SETTING: Pediatric intensive care unit of an academic medical center. PATIENTS: Eleven pediatric liver and/or intestinal transplant patients. INTERVENTIONS: Extemporaneously prepared 0.5 mg/kg omeprazole suspension every 12 hrs via nasogastric tube before sequential measurements of omeprazole serum concentration and gastric pH monitoring. Gastric pH was monitored continuously for 48 hrs and plasma omeprazole concentrations were determined upon first and multiple dosing. MEASUREMENTS AND MAIN RESULTS: Mean onset of action of omeprazole in a sodium bicarbonate vehicle was 62 +/- 82 mins (range, 2-226 mins). Subjects <4 yrs of age exhibited a more variable onset of omeprazole action (range, 3-226 mins) when compared with older subjects (onset of action, 2-40 min). Omeprazole maximum concentration and area under the concentration-time curve for the dosage interval were significantly greater upon multiple dosing when compared with the first dose. Mean baseline gastric pH in this study population was 1.0 +/- 0.8. Gastric pH remained >4.0 for 78.8% +/- 18.9% of the first dosage interval and 97.8% +/- 5.4% of multiple dosage intervals regardless of age when administered twice daily as a suspension. CONCLUSION: These results support the use of omeprazole administered twice daily as a suspension to maintain gastric pH of >4.0 and to achieve maximal pharmacodynamic effect in pediatric liver and/or intestinal transplant patients.

High-performance liquid chromatographic assay for the simultaneous determination of lansoprazole enantiomers and metabolites in human liver microsomes

In this study, a simple, sensitive and enantioselective HPLC method was developed for the simultaneous determination of lansoprazole enantiomers: a proton pump inhibitor, and its major metabolites: 5-hydroxylansoprazole and lansoprazole sulfone in human liver microsomes. After extraction from the microsomal incubation mixture with a diethyl etherdichloromethane (7:3, v/v) mixture, analytes were measured by reversed-phase HPLC on a Chiralcel OD-R column. Detection was made using an ultraviolet absorbance detector set at a wavelength of 285 nm. The mobile phase consisted of a methanol-water (75:25, v/v) mixture. At a flow-rate of 0.5 ml/min, the total run time was 35 min. The limit of quantification for both lansoprazole enantiomers was 0.25 microM and for the metabolites 0.13 microM. The method is suitable for the analysis of lansoprazole enantiomers and its metabolites from human microsomal liver incubations.

CYP2C19 genotype and pharmacokinetics of three proton pump inhibitors in healthy subjects

PURPOSE

To predict the CYP2C19 genotype-dependence in anti-Helicobacter pylori (H. pylori) therapy when lansoprazole or rabeprazole was used instead of omeprazole as a proton pump inhibitor (PPI).

METHODS

A comparative pharmacokinetic study with each PPI was designed as an open, randomized, and crossover study of 18 Japanese healthy volunteers who were classified into the homozygous, heterozygous extensive metabolizer and the poor metabolizer based on the CYP2C19 genotype determined by PCR-RFLP method. Each subject received a single oral dose of 20 mg omeprazole, 30 mg lansoprazole, or 20 mg sodium rabeprazole, with at least 1 week washout period between treatments. Plasma concentrations of PPIs and their metabolites were monitored until 12 h after medication.

RESULTS

Pharmacokinetic profiles of omeprazole and lansoprazole were well correlated with the CYP2C19 genotype. The heterozygous extensive metabolizer was slightly different from the homozygote, but there was no statistically significant difference. The CYP2C19 genotype dependence found for lansoprazole was not obvious compared with omeprazole. As for rabeprazole, the pharmacokinetic profile was independent of the CYP2C19 genotype.

CONCLUSIONS

CYP2C19 genotype dependence will be found in the anti-H. pylori therapy even when lansoprazole is used as the PPI.

A randomized, pharmacokinetic and pharmacodynamic, cross-over study of duodenal or jejunal administration compared to nasogastric administration of omeprazole suspension in patients at risk for stress ulcers

OBJECTIVES

The aim of this study was to characterize absorption and pH control of simplified omeprazole suspension (SOS), 2 mg/ml in 8.4% sodium bicarbonate, administered via the nasogastric versus jejunal or duodenal route.

METHODS

Nine critically ill surgical patients, NPO and mechanically ventilated, were enrolled in this randomized cross-over study. Patients received a single 40 mg dose of SOS by the nasogastric and either the jejunal or duodenal route. Twenty-four-hour continuous intragastric pH monitoring was performed during the study period. Sequential blood samples were collected over 24 h to characterize SOS absorption and pharmacokinetic parameters.

RESULTS

Nasogastric administration of SOS resulted in lower maximum mean +/- SD serum concentrations compared to jejunal/duodenal dosing (0.970 +/- 0.436 vs 1.833 +/- 0.416 microg/ml, p = 0.006). SOS absorption was significantly slower when administered via nasogastric tube (108.3 +/- 42.0 vs 12.1 +/- 7.9 min, p < 0.001). However, all routes of administration resulted in similar SOS area under the serum concentration-time curves (AUC(0-infinity)) (415.1 +/- 291.8 vs 396.7 +/- 388.1 microg x min/ml, p = 0.91) [corrected]. Mean intragastric pH values remained >4 at 1 h after SOS administration and remained >4 for the entire 24-h study (6.32 +/- 1.04, 5.57 +/- 1.15, nasogastric vs jejunal/duodenal, p = 0.015), regardless of administration route.

CONCLUSIONS

In critically ill surgical patients, pharmacokinetic parameters and subsequent pH control after the administration of SOS are similar by the jejunal, nasogastric, or duodenal route. SOS suspension offers an alternative acid control measure when patients are unable to take oral medications, yet have an enteral tube in place.

A new mechanism for anti-inflammatory actions of proton pump inhibitors--inhibitory effects on neutrophil-endothelial cell interactions

BACKGROUND

Neutrophil-endothelial cell interactions mediated by adhesion molecules may be involved in gastric mucosal inflammation associated with Helicobacter pylori or nonsteroidal anti-inflammatory drugs.

AIM

To investigate the effects of proton pump inhibitors and histamine-2 receptor antagonists (HRA) on neutrophil-endothelial cell adhesive interactions induced by H. pylori water extract (HPE) or interleukin-1beta (IL-1beta).

METHODS

Human peripheral neutrophils and umbilical vein endothelial cells were incubated with either proton pump inhibitors (lansoprazole and omeprazole) or HRA (famotidine and ranitidine). Neutrophil surface expression of CD11b and CD18 and endothelial cell intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) were assessed by flow cytometry and an enzyme immunoassay, respectively. Neutrophil adherence was defined as the ratio of exogenous neutrophils that adhered to the endothelial monolayers.

RESULTS

The expression of CD11b and CD18 on neutrophils and neutrophil-dependent adhesion to endothelial cells elicited by HPE were inhibited by lansoprazole and omeprazole at clinical relevant doses, and the expression of ICAM-1 and VCAM-1 on endothelial cells and endothelial-dependent neutrophil adherence induced by IL-1beta were also inhibited by lansoprazole and omeprazole at similar doses. Famotidine and ranitidine had no effect on neutrophil-endothelial cell interactions.

CONCLUSIONS

These results indicate that proton pump inhibitors can attenuate neutrophil adherence to endothelial cells via inhibiting the expression of adhesion molecules, suggesting that proton pump inhibitors may have anti-inflammatory activity.

Spectrophotometric methods for the determination of lansoprazole and pantoprazole sodium sesquihydrate

Spectrophotometric procedures for determination of two irreversible proton pump inhibitors, lansoprazole (I) and pantoprazole sodium sesquihydrate (II) are presented. Two methods were based on charge transfer complexation reaction of these drugs, where they act as n-donors, with either pi acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and with sigma acceptor as iodine. A third method was also investigated depending on ternary complex formation with eosin and copper (II). The colored products were quantified spectrophotometrically using absorption bands at 457 nm for DDQ (method A) at 293 and 359 nm for iodine (method B) and at 549 nm using ternary complex formation (method C), for both drugs. The molar combining ratio and the optimum assay conditions were studied. These methods determined the lansoprazole in concentration ranges from 10 to 90, 1.48 to 6.65 and 3.69 to 16.61 microg ml(-1) with mean percentage recovery 99.63% for DDQ, 99.71%, 99.18% for iodine and 99.76% for ternary complex and with relative standard deviation 0.11, 0.24, 0.13 and 0.36%, respectively. For pantoprazole, the concentration ranges were 10-60, 17.7-141.6 and 4.3-25.9 microg ml(-1) with mean percentage recovery 99.51, 98.97, 99.84 and 99.46% and relative standard deviation 0.53, 1.21, 0.65, 0.81% for the three mentioned methods, respectively. Investigation of the formed complexes was made with respect to its composition, molar ratio of the reaction, association constant K(C)AD, molar absorptivity epsilon(lambda)AD and free energy change deltaG for methods (A) and (B). The proposed methods have been applied successfully to the analysis of the cited drugs either in pure form or in pharmaceutical formulations, with good accuracy and precision, compared statistically with those given by the reported methods. They are recommended for quality control and routine analysis.

Determination of Lansoprazole in pharmaceutical dosage forms by two different spectroscopic methods

Two different ultraviolet (UV) spectroscopic methods were developed for determination of Lansoprazole in pharmaceutical dosage forms. The solutions of the standard and the sample were prepared in 0.1 M NaOH and phosphate buffer pH 6.6. Both UV spectrophotometric and derivative spectroscopic techniques were applied. Second-order derivative spectra were generated between 200 and 400 nm at N = 9, deltalambda = 31.5. The linear range for the UV spectrophotometric method was 3.0-25.0 microg ml(-1) and that for the derivative spectroscopic method was 0.5-25.0 microg ml(-1). The developed methods were applied to three different pharmaceutical preparations. The percentage recovery was 100.2%.

Determination of lansoprazole in biological fluids and pharmaceutical dosage by HPLC

A simple and rapid (extractionless) high-performance liquid chromatographic method with UV detection at 230 nm was developed for the determination of lansoprazole in biological fluids and pharmaceutical dosage. Niflumic acid was added as internal standard. The separation was performed at ambient temperature on a C18 Spherisorb column with acetonitrile + 0.1 M sodium acetate (40:60, v/v, pH 7) as mobile phase. The retention time was 5.2 min for niflumic acid and 6.7 min for lansoprazole. The detection limit was 20 ng/ml using a 100 microl loop. The method was successfully applied to a pharmacokinetic study of lansoprazole in humans.

Lansoprazole pharmacokinetics in subjects with various degrees of kidney function

The pharmacokinetics of lansoprazole, a new benzimidazole proton pump inhibitor, was evaluated after multiple-dose oral administration to 20 subjects with various degrees of kidney function. Multiple blood samples were obtained after doses 1 and 7 of the once-daily seven-dose regimen, and plasma concentrations of lansoprazole and five metabolites were quantitated with use of HPLC. The free fraction of lansoprazole increased as kidney function declined. A significant, although weak, relationship existed between creatinine clearance (CLCR) and area under the plasma concentration versus time curve (AUC) and terminal disposition half-life (t1/2), calculated with total concentration data. Those individuals with lower CLCR values also had lower total AUC and t1/2 values. However, there was no statistically significant relationship between CLCR and peak plasma concentration or AUC, calculated with unbound concentration data. No adjustment of lansoprazole dose is recommended on the basis of impaired kidney function.

Determination of R(+)- and S(-)-lansoprazole using chiral stationary-phase liquid chromatography and their enantioselective pharmacokinetics in humans

PURPOSE

Stereoselective and sensitive methods employing chiral stationary phase columns for HPLC determination of enantiomers of lansoprazole in the human serum were developed and pharmacokinetic behaviors of the enantiomers were evaluated in seven subjects.

METHODS

Five chiral stationary phase columns: Chiralcel OD (cellulose tris(3,5-dimethyl-phenylcarbamate)), OF (cellulose tris(4-chlorophenylcarbamate)), OG (cellulose tris(4-methylphenylcarbamate)) and OJ (cellulose tris(4-methylbenzoate)), and Chiralpak AS (amylose tris ((S)-1-phenylethylcarbamate)) were investigated.

RESULTS

Chiralcel OD and Chiralpak AS columns gave a good resolution of R(+)- and S(-)-enantiomers from racemic lansoprazole, but Chiralcel OF, OG, and OJ did not. The mean Cmax and the AUC values of R(+)-enantiomer were 3-5 times greater than those of S(-)-enantiomer following oral administration of 30 mg of racemic lansoprazole. The CLtot values of R(+)-enantiomer were significantly smaller than those of S(-)-enantiomer. Binding of R(+)-enantiomer to human serum proteins was significantly greater than that of S(-)-enantiomer. The mean metabolic ratio (metabolites/parent compound) in human liver microsomes of S(-)-enantiomer was significantly greater than that of R(+)-enantiomer.

CONCLUSIONS

The stereoselective pharmacokinetics of lansoprazole enantiomers is likely due to its stereoselective protein binding and/or metabolism.

Growth inhibition of Ureaplasma urealyticum by the proton pump inhibitor lansoprazole: direct attribution to inhibition by lansoprazole of urease activity and urea-induced ATP synthesis in U. urealyticum

The proton pump inhibitors (PPIs) omeprazole and lansoprazole and the acid-activated analog of lansoprazole AG-2000, which potently inhibit the urease of Helicobacter pylori (K. Nagata, H. Satoh, T. Iwahi, T. Shimoyama, and T. Tamura, Antimicrob. Agents Chemother. 37:769-774, 1993), also inhibited the urease activities of cell-free extracts as well as intact cells of Ureaplasma urealyticum. The 50% inhibitory concentrations were between 1 and 25 microM. These compounds also inhibited the ATP synthesis induced by urea in ureaplasma cells. The 50% inhibitory concentrations for ATP synthesis were close to those for urease activity, but they were lower than those of urease inhibitors, such as acetohydroxamic acid, hydroxyurea, and thiourea. In addition, one of the metabolites of lansoprazole found in human urine, M-VI, also inhibited ureaplasmal urease activity and the ATP synthesis induced by urea at almost the same concentrations as those of lansoprazole. The inhibition of PPIs against ureaplasma urease was very similar to those against H. pylori urease, suggesting that the inhibitory mechanism against these ureases was due to the blockage of the SH residues on the cysteine of the enzyme. Omeprazole, lansoprazole, AG-2000, and M-VI inhibited the growth of U. urealyticum. Since ureaplasma urease is thought to be involved in the pathogenicity of this organism in the urogenital tract, PPIs and their analogs may be useful as chemotherapeutic agents against diseases caused by U. urealyticum.

Determination of lansoprazole and five metabolites in plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the determination of lansoprazole, a new proton-pump inhibitor, and five of its metabolites in human plasma is described. Lansoprazole, its metabolites, and internal standard (omeprazole) were extracted into diethyl ether-methylene chloride and separation was obtained using a reversed-phase column under isocratic conditions. The method features monochromatic ultraviolet detection at 285 nm, and single extraction, single evaporation sample handling. The lower limit of quantitation, based on standards with acceptable coefficients of variation, was 10 ng/ml for all compounds. No endogenous compounds were found to interfere. This method has been demonstrated to be suitable for pharmacokinetic studies in humans.

Clinical pharmacokinetics of lansoprazole

Lansoprazole, a benzimidazole derivative with antisecretory and antiulcer activities, inhibits the acid pump activity at the final stage of the enzyme process and therefore reduces the acid secretion of parietal cells. Lansoprazole is converted to active metabolites in the acid environment of these cells. It is rapidly absorbed from a gastric acid-resistant formulation and is approximately 97% bound in human plasma. Single dose pharmacokinetics of lansoprazole appear to be linear over the range from 15 to 60mg. Food and time of dose influence absorption after single doses, but do not modify the antisecretory effect of multiple doses. Lansoprazole is extensively metabolised following oral administration into sulphone and 5-hydroxylated metabolites by the cytochrome P450 enzymes CYP3A4 and CYP2C18. Two other metabolites have been identified in plasma: sulphide and hydroxylated sulphone. Mean plasma elimination half-life (t1/2) is between 1.3 and 2.1 hours in healthy volunteers. 15 to 23% of the total dose is found in urine as free and conjugated hydroxylated metabolites, while unchanged lansoprazole is not detected. The pharmacokinetic profile of the drug is not modified by multiple administration. In healthy elderly volunteers, area under the plasma concentration-time curve (AUC) and t1/2 are significantly greater after single administration occurs to the same extent as in young volunteers. Renal failure has no influence on the pharmacokinetics of lansoprazole, but severe hepatic failure causes a significant decrease in clearance and an increase in the AUC and t1/2 of lansoprazole. This is accompanied by modifications in the AUC of metabolites, but severe hepatic failure has minimal effect on accumulation of the drug after multiple administration. The pharmacokinetics of lansoprazole in patients with acid-related disorders do not differ from those in healthy volunteers. Studies of interactions of lansoprazole with warfarin, prednisone, theophylline, phenazone (antipyrine), diazepam, phenytoin and oral contraceptives suggest minimal risk of any clinically significant interaction.

Determination of omeprazole in rat plasma by HPLC with column switching

A new high-performance liquid chromatographic method with column switching has been developed for the determination of omeprazole in plasma. The plasma samples were injected onto a Bondapak phenyl/corasil (37-50 microns) precolumn and polar plasma components were washed with 0.06 M borate buffer. After valve switching, the concentrated drug were eluted in the back-flush mode and separated on a mu-Bondapak C18 column with acetonitrile-phosphate buffer as the mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.01 microgram/ml-1. Total analysis time per sample was less than 20 min and the coefficients of variation for intra and inter-assay were less than 5.63%. This method has been successfully applied to plasma samples from rats after oral administration of omeprazole.

Age-related differences in the pharmacokinetics and pharmacodynamics of lansoprazole

1. The pharmacokinetics and pharmacodynamics of lansoprazole, an antisecretory and antiulcer agent, were evaluated in 12 older (> 60 years) and 12 younger (< 60 years) healthy men. 2. Doses of lansoprazole (15 or 30 mg) or placebo were each given once daily for 7 consecutive days in this randomized, double-blind, three-way crossover study. Plasma concentrations and urinary excretion of lansoprazole and its metabolites, and gastric acid secretion were monitored after dosing on days 1 and 7 of each treatment period. 3. Within each age group, lansoprazole pharmacokinetics were linear. The mean clearance and elimination half-life of lansoprazole were about 40% lower and higher, respectively, in the older subjects (CL0: 12-14 vs 20-24 1 h(-1); t1/2,z: 1.90-2.19 vs 1.26-1.44 h). 4. At each dose level, acid secretion was more inhibited in the older group. However, the AUC associated with a 50% decrease in acid secretion was similar (849 vs 892 ng ml(-1) h) for both age groups. Multiple dosing decreased the maximum possible inhibition more in the older group than in the younger group. 5. Since the decrease in acid output associated with equivalent AUCs on day 1 was similar for the two age groups, the greater difference between day 1 and day 7 secretion in the older group indicates that recovery of secretory activity may decline with increasing age.

Lansoprazole. A review of its pharmacodynamic and pharmacokinetic properties and its therapeutic efficacy in acid-related disorders

Lansoprazole is an effective acid pump inhibitor acting at the final enzymatic step of the acid secretory pathway of the parietal cell, decreasing gastric acid secretion regardless of the primary stimulus. Results of short term (less than 8 weeks) clinical trials have shown lansoprazole to be significantly superior to placebo and ranitidine in the treatment of duodenal ulcer, both in the rate of healing and in overall healing at 4 weeks. Lansoprazole appears to heal duodenal ulcer more quickly than famotidine, and demonstrates slightly greater efficacy at 4 weeks, although both drugs appear to have equivalent efficacy overall. Gastric ulcers and reflux oesophagitis are also healed by lansoprazole 30 mg/day for 4 to 8 weeks, with healing rates after 8 weeks of approximately 85 to 95% for both indications. Lansoprazole appears to be superior to ranitidine and comparable to omeprazole in treating reflux oesophagitis. Furthermore, lansoprazole has relieved reflux symptoms more quickly than either ranitidine or omeprazole. Preliminary data also indicate that lansoprazole may be effective in the treatment of peptic ulcer disease and reflux oesophagitis refractory to H2-receptor antagonists, and in patients with Zollinger-Ellison syndrome. While direct comparisons with omeprazole are limited, results suggest that lansoprazole, used for short term treatment, is at least as effective as omeprazole in the treatment of peptic ulcer and reflux oesphagitis. Lansoprazole has been well tolerated in short term clinical trials, with an incidence of adverse effects comparable with that of other agents in its therapeutic class. Trials assessing long term tolerability data are ongoing and will be required as part of the assessment of the safety profile, if lansoprazole is to be used prophylactically to prevent ulcer recurrence. Thus, by virtue of its ability to heal ulcers and rapidly relieve associated symptomatology, lansoprazole represents a useful alternative for the treatment of acid related disorders.