Scandinavian Journal of Gastroenterology
`
`ISSN: 0036-5521 (Print) 1502-7708 (Online) Journal homepage: http://www.tandfonline.com/loi/igas20
`
`Pharmacokinetics and metabolism of omeprazole
`in animals and man - an overview
`
`C-G Regårdh, M Gabrielsson, K-J Hoffman, I Löfberg & I. Skånberg
`
`To cite this article: C-G Regårdh, M Gabrielsson, K-J Hoffman, I Löfberg & I. Skånberg (1985)
`Pharmacokinetics and metabolism of omeprazole in animals and man - an overview, Scandinavian
`Journal of Gastroenterology, 20:sup108, 79-94, DOI: 10.3109/00365528509095821
`To link to this article: http://dx.doi.org/10.3109/00365528509095821
`
`Published online: 08 Jul 2009.
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`DRL EXHIBIT 1029 PAGE 1
`
`

`

`79
`
`Pharmacokinetics and metabolism of omeprazole
`in animals and man - an overview
`
`REGARDH C-G, GABRIELSSON M,
`
`HOFFMAN K-J, L~~FBERG I, SKANBERG I.
`Department of Pharmacokinetics and Drug
`Metabolism,
`A B Hassle, Molndal, Sweden.
`RegArdh C-G, Gabrielsson M, Hoffman K-3, Liifberg I, SkAnberg I. Phar-
`macokinetics and metabolism of omeprazole in animals and man - an over-
`view. Scand J Gastroenterol 1985;2O(suppl 108):79-94.
`The pharmacokinetics of omeprazole have been studied to varying extent in the mouse,
`rat, dog and in man.
`The drug is rapidly absorbed in all these species. The systemic availability is relatively
`high in the dog and in man provided the drug is protected from acidic degradation in the
`stomach. In man the fraction of the oral dose reaching the systemic circulation was found
`to increase from an average of 40.3 to 58.2 Vo when the dose was raised from 10 to 40 mg,
`suggesting some dose-dependency in this parameter.
`The drug distributes rapidly to extra-vascular sites. The volume of distribution, Vp, in
`man is comparable to the volume of the extracellular water. The penetration into the red
`cells is low, the ratio between the concentration in whole blood and in plasma being about
`0.6. Omeprazole is bound to about 95 Va to proteins in human plasma. The binding is
`lower in the dog and rat (90 and 87 Vo, respectively).
`Omeprazole is eliminated almost completely by metabolism and no unchanged drug has
`been recovered in the urine in the species studied. Two metabolites, characterised as the
`sulfone and sulfide of omeprazole, have been identified and quantified in human plasma.
`The mean elimination half-life in man and in the dog is about 1 hour, whereas half-lives
`in the range of 5 to 15 minutes have been recorded in the mouse. In two studies in man,
`the mean total body clearance was 880 and 1097 ml x min-l, indicating that omeprazole
`belongs to the group of high clearance drugs. In the dog, too, the drug appears to be rapid-
`ly cleared from the blood, the mean total body clearance being about 10.5 ml x min-' x
`kg-l .
`In the rat and dog, 20 to 30 To of an i.v. or oral dose of omeprazole is excreted as
`metabolites in the urine and the remaining fraction is recovered in the faeces within three
`days after the administration. in man, the excretion of radioactivity via the kidneys is
`much more efficient and the recoveries in the excreta are approximately the reverse of
`those in the rat and dog.
`In vifro studies with rat liver microsome preparations suggest that omeprazole and
`cimetidine inhibit cytochrome P-450-mediated metabolic reactions to about the same ex-
`tent in equimolar concentrations. However, since the molar daily dose of cimetidine will
`be 25 to 50 times higher than that of omeprazole, the latter might have less influence on
`the mixed function oxidase system than cimetidine. Results obtained in man with an-
`tipyrine and aminopyrine support this hypothesis.
`
`Key-words: Pharmacokinetics; disposition; metabolism; proteinbinding; drug interac-
`tions; animals; man
`Regardh C-G, Ph.D. Dept of Pharrnacokinetics ond Drug Metabolism, Hassle Research
`Laboratories, S-431 83 Molndal, Sweden.
`
`Introduction
`is a substituted benzimidazole
`benzimidazole
`which inhibits gastric acid secretion in animals and
`-2-[[(4-methoxy -3,5- man. The drug acts via an interaction with
`Omeprazole, 5-methoxy
`sulphinyl1lH- H'K'ATPase - the gastric proton pump - in the
`dimethyl
`-2-pyridinyl) methyl]
`
`DRL EXHIBIT 1029 PAGE 2
`
`

`

`80
`
`secretory membrane of the parietal cell (1). A single,
`oral dose of 20 to 80 mg omeprazole induces a dose-
`dependent
`and
`long-lasting
`inhibition
`of
`pentagastrin-stimulated gastric acid secretion in
`healthy volunteers (2, 3). The inhibitory effect o n
`this parameters is further strengthened during the
`first days of repeated administration (2 - 4).
`Effect studies over 24 hours have revealed a pro-
`found decrease in intragastric acidity throughout
`the study period (5, 6).
`When omeprazole has been given to duodenal ulcer
`patients, the recovery frequency has been extremly
`high. After four weeks of treatment, the healing
`rate has been over 90 Vo (7, 8). On the basis of
`these initial clinical studies omeprazole thus ap-
`pears to be an effective drug in the treatment of
`duodenal ulcer. Its therapeutic potential is now be-
`ing further assessed in comparative, clinical trials.
`In this paper our present knowledge concerning the
`pharmacokinetics of omeprazole in various species
`is summarised.
`
`Animal pharmacokinetics
`Studies in the mouse
`The plasma concentrations of omeprazole have
`been followed after oral administration of a single,
`oral dose of 40 and 400 pmol/kg to groups of 5
`starved, male mice, which were killed at various
`times after theadministration. The doses wereiden-
`tical to the lowest and highest dose in the
`cancerogenicity study in this species and the same
`formulations were used. Omeprazole was analysed
`In plasma samples from each animal by liquid-solid
`chromatography and UV-detection (10).
`Maximum plasma concentration was already
`recorded in the first sample drawn, i.e., 10 minutes
`after dosage, whereafter the concentration of
`omeprazole declined very rapidly to minimum
`detectable levels 0.5 and 2 hours after gavage. The
`mean maximum concentration increased from 15.9
`r4 5.3 pmol/l after the lowest dose to 155.4 zk 24.5
`pmol/l after the dose of 400pmol/kg, i.e., the con-
`centration increased proportionally to the amount
`of drug administered. Estimated mean half-lives
`were in the range of 5 to 15 minutes with a tendency
`towards a longer half-life for the highest dose.
`
`The distribution of omeprazole and its metabolites
`in the mouse has been studied by autoradiography
`and by liquid scintillation counting of various
`tissues (11).
`Studies in the rat
`The absorption, excretion and tissue distribution of
`omeprazole have been studied in rats after intra-
`venous and oral administrations of I0 and 100
`pmol/kg, respectively, to male, unstarved Sprague-
`Dawley rats. The doses contained trace amounts of
`i4C-labelled drug. The radiochemical purity was
`>99 Vo determined by liquid-solid chromatog-
`raphy.
`Radioactivity measurements were performed ac-
`cording to the following procedures using Insta-
`Gel@, alternatively Dimilume0-30, as scintillation
`liquid. Faeces homogenates were combusted by a
`mixture of concentrated hydrogen peroxide (30 Vo)
`and perchloric acid (70 To) and blood was hemo-
`lysed in Soluene@-350/isopropranolol (1:l) and
`decolourised by hydrogen peroxide (30 To) prior to
`the addition of the scintillation liquid. Tissue
`homogenates were dissolved in 1 ml Soluene@-350.
`Counting was performed in a Mark I11 Model 6880
`(Searle Analytical Inc.) liquid scintillation spec-
`trometer. Quenching was corrected for by external
`standardisation.
`Recovery of the radioactive dose in
`urine and faeces
`The urinary and fecal excretions of the radioactive
`i.v. and oral doses are given in Table I. After i.v. ad-
`ministration 25.9 Vo of thedose was excreted via the
`kidneys over a period of 72 hours, while the average
`cumulative urinary recovery of the oral dose during
`the same period was 22.7 Vo. In both experiments,
`more than90 Vo of the total urinary recovery was ex-
`creted during the first 24 hours after dosage. The
`corresponding recoveries in the faeces over the en-
`tire collection period were 71.9 and 73.1 % of the i.v.
`and oral doses, respectively. Less than 0.1 Vo of the
`amount excreted via the kidneys was due to un-
`changed omeprazole.
`These data indicate a complete gastrointestinal up-
`take of the radioactive oral dose, but further studies
`are needed for evaluation of the systemic availabil-
`ity of omeprazole in the rat.
`
`DRL EXHIBIT 1029 PAGE 3
`
`

`

`Table I. The excretion of ['TI omeprazole and its total pool of metabolites after intravenous and oral administrations
`of 10 pmol/kg and 100 pmol/kg, respectively, to the rat. Mean values f SD from 4 rats.
`
`81
`
`Route of ad-
`ministration
`
`Time
`(h)
`
`i.v.
`
`p.0.
`
`~~
`
`0- 6
`6-24
`24 - 48
`48 - 72
`0-72
`
`0- 6
`6-24
`24 - 48
`48 - 72
`0-72
`
`Recovered radioactivity 70 of dose
`
`Urine
`
`19.0k 1 .O
`6 . 0 f 1.4
`0.7f0.1
`0.2f0.1
`25.9f2.0
`
`16.0f 1.9
`5.0f0.4
`1.4f0.6
`0.3f0.1
`22.7k 1.5
`
`Faeces
`
`0.6f0.4
`68.0k6.0
`2.8f0.8
`0.5f0.3
`71.9f4.2
`
`0.2f0.2
`48.2f9.7
`20.8f7.6
`3.9f2.8
`73.1k4.4
`
`Total
`
`19.6f1.8
`74.0f3.9
`3.5f0.8
`0.7f0.4
`97.8f4
`
`16.2f 1.9
`53.0f9.5
`22.4f 7.6
`4.2k2.8
`95.8k2.3
`
`Tissue distribution of [ I4C]ome-
`prazole and its metabolites
`
`The concentrations of radiochemical entities have
`been determined in 15 different tissues of the rat at
`various times after i.v. and oral administrations of
`[14C]omeprazole. Table I1 shows the results for the
`i.v. dose. After 0.5 hours the highest concentrations,
`12 to 23 nmol/g tissue, were found in the liver,
`kidneys and duodenum. The -stomach and the
`
`thyroid gland also contained comparatively high
`amounts of radioactivity. In all other tissues
`studied, the concentration of omeprazole plus
`metabolites was lower than in whole blood and
`plasma (- 3.5 nmol/g). Particularly the brain con-
`tained low levels of radioactivity suggesting that
`omeprazole and/or its metabolites pass the blood
`brain barrier to a very limited extent. The high
`recovery of radioactivity in the stomach agrees with
`observations in the whole-body autoradiographic
`
`Table 11. Tissuedistribution and retention of total radioactivityin the rat after intravenous administration of lOpmol/kg
`of [14] omeprazole. Mean values f SD from 4 rats in nmol/g organ.
`
`Tissue
`
`Blood
`Plasma
`Heart
`Lungs
`Liver
`Kidneys
`Brain
`Thymus
`ds
`Salivary glans
`Thyroid
`Stomach
`Duodenum
`Spleen
`Fat (white)
`Muscle
`
`Mean weight of
`4 rats (g)
`
`Time after administration
`
`0.5 h
`
`72 h
`
`Minimum
`detectable
`concent ration
`
`3.2f1.0
`3.6k 1.4
`1.9f0.6
`2.2f0.6
`13.Ot4.0
`12.0f4.0
`0.3kO.l
`1.3f0.8
`1.8f0.6
`5.2f0.8
`8.6t3.0
`23.0f6.0
`2.2 f 0.2
`0.6f0.2
`1.3f0.4
`
`0.79f0.06
`0.03f0.02
`0.09f0.01
`0.12f0.02
`0.34f0.04
`0.28f0.02
`<M.d.c.
`<M.d.c.
`<M.d.c.
`0.30f0.12
`0.09f0.2
`<M.d.c.
`0.19k0.04
`<M.d.c.
`0.03 f 0.02
`
`0.004
`0.002
`0.04
`0.04
`0.01
`0.02
`0.03
`0.09
`0.1
`0.07
`0.04
`0.2
`0.06
`0.07
`0.02
`
`250
`
`270
`
`M.c.d. = minimum detectable concentration
`
`DRL EXHIBIT 1029 PAGE 4
`
`

`

`82
`
`study of the mouse in which it was found that
`omeprazole was concentrated in the mucosal cells
`of the stomach (11).
`Secretion into the bile or directly over the intestinal
`epithelium probably accounts
`for
`the high
`duodenal content of radioactivity after the i.v. dose.
`Insignificant amounts of unchanged omeprazole
`were recovered in the bile in a subsequent study,
`suggesting that the radioactivity in the duodenum
`of the rat is primarily due to metabolites. About
`75 Yo of the given i.v.
`radioactive dose was
`recovered in the faeces over a period of 72 hours.
`The distribution pattern of the oral dose was very
`similar to that of the i.v. dose though, as a conse-
`quence of the route of administration, the stomach
`and duodenum contained the highest amount of
`radioactivity during the first 6 hours following the
`administration.
`The levels of unchanged omeprazole in the plasma
`0.5 hours after the i.v. and oral dose were 9 and 6 To
`of the total radioactivity, respectively. Six hours
`after the administration the proportion of un-
`changed drug in the plasma had further decreased
`about tenfold.
`
`Studies in the dog
`The pharmacokinetics of omeprazole have been
`studied in the dog to varying extents in several
`studies.
`
`Design of Study I
`In the initial study (12) three dogs with gastric-
`duodenal fistulas were given 0.25 pmol/kg i.v. via
`the vena antibrachi or intraduodenally via a
`duodenal fistula. Another three dogs provided with
`a Heidenhain pouch received 1.0 pmol/kg by a
`stomach tube. Gastric acid secretion was induced in
`all dogs by continuous subcutaneous infusion of
`histamine, 150 to 400 nmol/kg/h, throughout the
`experiment. The dogs were deprived of food and
`water for about 18 hours prior to the start of the ex-
`periment.
`The i.v. dose, dissolved in 40 To PEG 400 and 4 mM
`bicarbonate buffer (pH = 8), was given over a
`period of 1 to 2 minutes. ~h~ oral and intra-
`duodenal doses were suspended in 0.5 Yo of a
`
`MethoceP-water solution (0.5 To). Each dose con-
`tained a tracer dose of [14C]omeprazole.
`Omeprazole was determined in plasma according
`to the method of Persson et a1 (10).
`Results and discussion
`The mean plasma concentration-time curves of all
`three doses are shown in Figure 1. Following the i.v.
`dose the omeprazole plasma levels declined bi-
`exponentially in each dog. The average half-life of
`the terminal phase (ti,@) was 62 minutes and the
`average volume of distribution, VB, was 0.56 Vkg,
`i.e., about half of the actual body space. Total
`plasma clearance, determined by the ratio between
`the dose and the integrated area under the plasma
`6.3
`concentration-time-curve
`(AUC) was
`the ratio between
`ml x min-Ikg-l. Since
`the
`blood and plasma concentration of omeprazole is
`0.60 in the dog (Table VII), the total body clearance
`of omeprazole in the dog would be about 10.5
`ml x min-I kg-l.
`
`The intraduodenal dose of omeprazole was very
`rapidly absorbed. Maximum concentration was
`already attained during the first 5 to 15 minutes
`post dosage. The fraction of this dose available to
`
`Plasma concentration
`II mnlll
`1 .o
`
`0.10
`
`0.01
`
`3
`2
`h
`4
`0
`1
`Figure 1. Plasma concentrations of ['4C] omeprazole
`Or i d . (0.25 pmol/kg,
`given i.V. (0.25 W O W % n = 2,
`n = 3, W) in thegastric fistula dog and orally (1 qol/kg,
`n = 3, 0) in the Heidenhahn pouch dog. MeanfSEM.
`
`
`
`DRL EXHIBIT 1029 PAGE 5
`
`

`

`83
`
`the systemic circulation was, on average, about 70
`070 determined by AUC comparisons. The mean
`half-life in the terminal phase of the plasma
`concentration-time-curve was essentially the same
`as for the i.v. dose, i.e., approximately one hour.
`Compared with the intraduodenal dose, intra-
`gastric administration resulted in a lower rate of
`absorption and a reduction
`in the systemic
`availability. Maximum concentration was obtained
`from 30 to 75 minutes after administration and the
`AUC was only about 15 070 of that of a correspond-
`
`ing i.v. dose of omeprazole. The terminal half-life
`was again close to one hour. The difference between
`the fraction of the intraduodenal and intragastric
`dose available to the systemic circulation is prob-
`ably a consequence of acidic degradation of
`omeprazole in the histamine-stimulated stomach.
`
`The average plasma concentration-time profiles of
`the total pool of radioactive metabolites following
`all three doses are shown in Figure 2. The radioac-
`tivity due to the metabolites declined essentially
`
`1 .o
`
`0.8
`
`0.6
`
`0.4
`
`0.2
`
`0.1
`
`(
`
`0
`
`3
`h
`4
`2
`1
`Figure 2. Plasma concentrations of radioactive metabolites following administration of [14C] omeprazole i.v. (0.25
`pmol/kg, n = 2, a) or i.d. 0.25 pmollkg, n = 3, H) in the gastric fistula dog and orally (I pmol/kg, n = 3, 0) in the
`Heidenhan pouch dog. Meanf SEM.
`
`
`
`DRL EXHIBIT 1029 PAGE 6
`
`

`

`84
`
`mono-exponentially in each dog during the last two
`hours of each experiment. Estimated half-lives dur-
`ing this period were unrelated to the route of ad-
`ministration and ranged between 2.7 to 5.0 hours,
`i.e., in the dog some metabolite(s) is/are eliminated
`at a lower rate than that of the parent drug.
`Design of Study I1
`This study was performed to measure the excretion
`of [14C]omeprazole and its metabolites in the urine
`and faeces, following i.v. and oral administration of
`0.25 and 1.0 pmol/kg, respectively, to three dogs.
`The doses were given cross-over at least two weeks
`apart. The dogs had fasted for 18 hours prior to
`drug administration. Food and water were acces-
`sible 6 hours post dosage. The oral dose was given
`by an intragastric tube and the animals were kept in
`metabolic cages permitting separate collection of
`urine and faeces over a 72 hour period. The concen-
`tration of [14C]omeprazole and its radioactive
`metabolites was determined by methods previously
`described in the rat study.
`Results and comments
`Totally, 87 Vo of the i.v. and 95 VO of the oral dose
`were recovered in the excreta over a three-day
`period, Table 111. During this time 32 Vo of the i.v.
`dose was excreted in the urine. The corresponding
`recovery of the oral dose was 21 Vo. The major frac-
`tion recovered in urine and faeces was excreted dur-
`ing the first 24 hours after the administration. Dur-
`ing this period more than 80 Vo of the 72-hour
`
`urinary recovery of both doses was excreted in the
`urine. Approximately 2/3 of the three-day fecal
`recovery was expelled with the faeces during the
`first 24 hours after both i.v. and oral ad-
`ministration.
`In both experiments, the excretion of unchanged
`[14C]omeprazole in the urine was less than 0.5 To.
`No attempt was made to quantify unchanged drug
`in the faeces. However, preliminary analysis of bile
`from three bile-fistulated dogs has not revealed any
`unchanged omeprazole in the bile. Accordingly,
`omeprazole seems to be eliminated primarily by
`biotransformation in the dog. The metabolites are
`excreted rapidly via the kidneys, in the bile and/or
`over the gastrointestinal epithelium.
`Human pharmacokinetics
`Two basic pharmacokinetic studies and one interac-
`tion study with aminopyrine and antipyrine have
`been completed in man until now.
`Balance study with single i.v.
`and oral [ 4C]omeprazole
`Study design
`The absorption and disposition of i.v. and orally ad-
`ministered omeprazole have been studied in a
`single-dose study with 10 mg i.v. and 20 mg orally
`(13). The radioactive dose was 20 pCi of I4C-
`labelled omeprazole. The doses were administered
`
`Table 111. Excretion of [l4C1 omeprazole and its radioactive metabolites in the dog following i.v. and oral administration
`of 0.25 and l.Oprnol/kg, respectively, of 14C-labelled drug. (MeankSD; n = 3).
`
`Dose
`
`i.v.
`
`oral
`
`~~
`
`Time
`h
`
`0-24
`24 - 48
`48 - 72
`0-72
`
`0-24
`24 - 48
`48 - 72
`0-72
`
`-
`Urine
`
`29.5-CO.7
`2.0 +0.9
`0.5 kO.1
`3 2 . 0 f 1 . 1
`
`~
`
`17.5rt6.4
`3 . 2 2 3 . 2
`0.5k0.3
`21.2f3.5
`
`Per cent of dose
`
`Faeces
`
`Total
`
`38.2f21.1
`15.2f12.6
`1.4& 0.7
`54.7+ 7.9
`
`67.7f21.8
`17.1 f 12.7
`1 . 9 f 0.8
`86.7+ 8.3
`
`~
`
`~~
`
`~
`
`~
`
`~~
`
`_ _ _ _ ~
`
`51.9f21.6
`1 6 . 0 f 9.6
`5 . 7 f 4.9
`7 3 . 6 f 12.3
`
`69.4k24.2
`19.2f12.2
`6 . 1 k 5.1
`94.7f13.3
`
`DRL EXHIBIT 1029 PAGE 7
`
`

`

`85
`
`Figure 3. Chemical structure of omeprazole and two metabolites identified in human plasma.
`
`randomised cross-over 1 to 4 weeks apart to eight,
`healthy, malevolunteers, 24 to 31 years of age. Both
`doses were administered dissolved in a mixture of
`PEG 400 and water. The subjects were pre-treated
`with 8 mmol NaHCO, 5 minutes prior to drug ad-
`ministration. Sixteen mmol of bicarbonate were
`given together with each dose and during the next
`30 minutes they received a further 8 mmol of bicar-
`bonate every tenth minute to prevent degradation
`of the oral dose by the acid in the stomach.
`
`[‘4C]omeprazole and the total pool of radioactive
`metabolites were measured in the plasma over 24-
`hours according to methods mentioned previous-
`ly. In addition, two identified metabolites with the
`code-numbers H 168/22 and H 168/66, Figure 3,
`were quantified in the plasma over the same period
`of time. The identification of these two metabolites
`is described below.
`
`Urine and faeces were collected quantitatively over
`a period of 96 hours and analysed for unchanged
`drug and metabolites according to previously
`described methods. The urine portions were ad-
`justed to pH 7 to 8 by 1 M NaHCO, to prevent
`acidic degradation of omeprazole while waiting for
`analysis.
`
`Identification of omeprazole
`and two metabolites in human
`plasma
`Pooled plasma samples from the individuals par-
`ticipating
`in
`the study were extracted with
`methylene chloride at pH 7.4. Aliquots of the
`organic phase were injected repeatedly onto a
`straight-phase LC column using 3.5 Vo methanol in
`methylene chloride as the mobile phase (10). The
`methanol contained 5 Vo of a solution of 25 Yo
`NH,. Fractions of the eluate with retention times
`identical to those of the references omeprazole,
`oxidised omeprazole (H 168/66, “omeprazole
`sulfone”) and reduced omeprazole (H 168/22,
`“omeprazole sulfide”) were collected. The “ome-
`prazole sulfide” fraction was further purified
`using 2 Vo methanol in methylene chloride as
`mobile phase. The methanol contained the same
`proportion of NH, as in the first mobile phase. Col-
`lected fractions were evaporated to dryness and the
`residue was dissolved in 25 p1 of methanol. The
`samples were then introduced into the mass spec-
`trometer (MAT 112, Bremen. W Germany) by a
`direct inlet system. The sample rod was heated ac-
`cording to the following temperature programme:
`
`DRL EXHIBIT 1029 PAGE 8
`
`

`

`86
`
`initial, rapidly declining distribution phase, tii2 a,
`ambient temperature for 10 seconds, 150°C for 35
`seconds and flush evaporation to 300°C for 75
`was 3.0 min (range 2.1 to 4.3 min). The drug was ini-
`itially distributed into a very limited fraction of the
`seconds. The sample rod was cooled to 30 “C before
`the next analysis. The measurement was performed
`available body space. The average volume initially
`in repetitive scanning or selected ion monitoring
`available for the distribution of omeprazole was
`mode. Identical retention times o n the LC column
`0.079 l/kg (range 0.052 to 0.139 l/kg, i.e., com-
`and the presence of significant ions in the mass
`parable with the blood volume. Also the apparent
`spectra of isolated plasma metabolite and syn-
`volume of distribution a t pseudo-distribution
`equilibrium, Vg, was relatively small. The mean
`thesised reference were taken as identity.
`value was 0.31 i/kg (range 0.19 to 0.45 I/kg, which
`The electron impact mass spectra of the isolated
`would be compatible with localisation of a major
`fractions of the human plasma having identical
`fraction of omeprazole in the extracellular water.
`retention times to those of synthesised omeprazole
`The ratio between the blood volume and V p sug-
`and H 168/66 are given in Figure 4. These spectra
`gests that about 25 To of the total amount of
`were in all details identical to those of the two
`omeprazole in the body is confined to the blood.
`reference compounds confirming the existence of
`unchanged omeprazole, and “omeprazole sulfone” Omeprazole was eliminated rapidly in all eight in-
`in human plasma.
`dividuals. The average half-life was about 60
`minutes (range 16 to 151 minutes). The total plasma
`The concentration of the metabolite with the same
`clearance varied between 59 to 828 ml x min-‘
`retention time as “omeprazole sulfide” was too low
`(mean value 530 ml x min-l). Since the average ratio
`in the plasma to yield a complete mass spectrum
`between the omeprazole concentration in blood
`like the one of the reference compound in Figure 5.
`and plasma is about 0.6 in man (see below), the
`Therefore, three characteristic ions; the molecular
`average total blood clearance of omeprazole was
`ion m/z329+, and (M-32y, and (M-32-15)+, were
`about 880 mlxrnirri in this study.
`used to improve the sensitivity of the mass spec-
`trometer by selected ion monitoring. A fragmen-
`The rapid elimination of omeprazole appears to be
`togram with the expected relative intensity of the
`primarily due to metabolic processes since in-
`three ions was obtained (Figure 5). The time for
`significant amounts of unchanged drug were ex-
`direct probe evaporation was the same for the
`creted via the kidneys and in the stools. On the
`metabolite as for the reference compound. Accord-
`average, 78.2 070 of the i.v. radioactive dose (range
`ing to these results, “omeprazole sulfide” can be
`74.3 to 81.9 070) was recovered in the urine over the
`assigned as a minor human plasma metabolite of
`collection period of four days. The corresponding
`recovery of the oral dose was 75.7 Yo (range 72.7 to
`omeprazole.
`78.6 070). During the same period the fecal excretion
`Results and comments
`was 19.3 Yo (range 15.0 to 24.3 Yo) for the i.v. dose
`and 18.3 To (range 13.6 to 20.7 070) after oral ad-
`The mean plasma concentration-time-curves
`ministration. The excretion of
`radioactive
`following the i.v. and oral doses of omeprazole are
`metabolites via the kidneys was initially very rapid
`shown in Figure 6. The oral solution of omeprazole
`and during the first six hours post dosage an
`was very rapidly absorbed. The average time of
`average of about 60 Yo of the administered radio-
`was 13.8 minutes (range 11 to 25
`peaking, t,,,,
`active dose was recovered in the urine after both i.v.
`minutes). The maximum Concentration varied
`and oral omeprazole.
`seven-fold from 660-4580 nmol/l (mean 1914
`nmol/l) and the mean systemic availability was
`Only a minor fraction -less than 1 070 -of the dose
`53.6 9’0 (range 24.9 to 117.0 070).
`was excreted via the kidneys as the metabolite H
`168/66. In spite of its low urinary recovery the
`The plasma levels of the i.v. dose declined bi-
`metabolite H 168/66 was, however, available in the
`exponentially with time in all eight subjects and
`plasma in relatively high concentration, suggesting
`gave excellent fits to the equation of the two-
`that this metabolite is either further metabolised
`compartment model on non-linear regression
`the kidneys or mainly
`before excretion via
`analysis. The mean half-life of omeprazole in the
`
`DRL EXHIBIT 1029 PAGE 9
`
`

`

`87
`
`260
`300 miz
`260
`2i0
`160
`160
`100
`280
`240
`140
`150
`Figure 4. Electron impact mass spectrum of omeprazole (A) and metabolite H 168/66 (B) isolated from
`human plasma.
`
`DRL EXHIBIT 1029 PAGE 10
`
`

`

`88
`
`Relative intensity
`
`50
`
`Intensity
`
`100
`
`150
`
`200
`
`R
`
`250
`
`300
`
`350
`
`:30
`
`:40
`
`150
`
`IiOO
`
`1.10
`
`1[20
`
`1:30
`
`1:40
`
`1'50
`
`. I 0
`
`:20
`
`200
`min
`Figure 5. Electron impact mass spectrum of reference compound H 168/22 (A) and selected ion monitoring of
`plasma metabolite H 168/22 (B).
`
`DRL EXHIBIT 1029 PAGE 11
`
`

`

`89
`
`3
`
`2
`
`1
`
`120 rnin
`20
`40
`60
`0
`100
`80
`Figure 6. Mean plasma concentrations of omeprazole following administration of single doses of 10 mg (28.95 pmol)
`i.v. ( 0 ) and 20 mg (57.90 pmol) orally (0) to 8 young healthy subjects. The bars indicate SEM.
`
`eliminated in the bile or by secretion over the
`gastrointestinal wall. Figure 7 shows the mean con-
`centrations of omeprazole, H 168/66, and uniden-
`tified metabolites in the plasma over the first 2
`hours following the i.v. dose of omeprazole. During
`this interval the concentrations of H 168/22 were
`consistently below minimum determinable levels
`(-30 nmol/l).
`Effect of dose on the phar-
`macokinetics of omeprazole
`Study design
`The effect of various i.v. and oral doses on the
`
`kinetics of omeprazole has been evaluated in ten
`healthy, male subjects 19 to 27 (mean = 25) years of
`age (14). The subjects were given 10 and 40 mg
`omeprazole i.v. and 10, 40 and 90 mg orally ran-
`domised and cross-over. The drug was administered
`dissolved in a mixture of PEG 400 and water, and
`the buffer intake in association with the administra-
`tion was the same as in the previous study.
`
`Results and comments
`The mean plasma concentration-time-curves of
`omeprazole following the oral doses are given in
`Figure 8. The maximum concentration and AUC
`
`DRL EXHIBIT 1029 PAGE 12
`
`

`

`90
`
`MmoM
`2.0
`
`1.0
`
`0.8
`
`0.6
`
`0.4
`
`0.2
`
`0.1
`
`30
`90
`120 min
`0
`60
`Figure 7. Mean plasma levels of omeprazole. and its metabolites following a single oral dose of 20 rng omeprazole
`(omeprazole (n = 8) (0) omeprazole; (0) H 168/66; (.)unidentified metabolites.
`
`increased disproportionately with the amount of
`drug administered, resulting in dose-dependent
`systemic availability. On average, 40.3 % (range
`14.9 to 73.4 To) of the oral 10 mg dose was available
`to the systemic circulation, while the value of this
`parameter increased to 58.2 070 (range 29.0 to
`105.0 %) for the 40 mg dose and further to 96.9 %
`(range 57.5 to 155.0 To) when 90 mg omeprazole
`was given orally.
`The increase in systemic availability by 44 %, when
`the oral omeprazole dose was raised from 10 to 40
`mg, appears to be caused primarily by a partial
`5aturation of the first-pass effect since the mean
`plasma clearance of the corresponding i.v. doses
`
`was unaffected by the dose (658 and 633 ml
`x min-l). On the other hand, the further increase
`in F to a mean value of almost 100 070 for the oral 90
`mg dose probably resulted from a continued satura-
`tion of the first-pass effect in combination with
`reduced systemic clearance. F-values in the range of
`140 to 160 070 in three individuals and a significant
`increase in the mean tih from 29 minutes for the 40
`mg dose to 45 minutes after 90 mg orally support
`this hypothesis. However, since this high dose was
`not given i.v., adjustments for potentially altered
`systemic clearance of the 90 mg dose in relation to
`the 10 and 40 mg i.v. dose could not be made in the
`calculations of F of the highest oral dose.
`
`DRL EXHIBIT 1029 PAGE 13
`
`

`

`91
`
`pmolll
`10
`
`5.0
`
`2.0
`
`1 .o
`
`0.5
`
`0.2
`
`0.1
`
`40
`
`80
`20
`60
`0
`Figure 8. Mean plasma levels of omeprazole following
`administration of 3 single oral doses of omeprazole (n =
`10 ). The bars indicate SEM.
`
`120
`100
`(*) 10 mg (28.95 pmol)
`(A) 40 mg (115.8 pmol)
`( e) 90 mg (260.6 pmol)
`
`140
`
`160
`
`180min
`
`Some disposition characteristic of the two i.v. doses
`derived according to the two-compartment model
`are presented in Table IV. Calculated parameters
`were in good agreement with those derived from the
`
`i.v. dose of [14C]omeprazole. There was no indica-
`tion of any dose-related changes
`in
`these
`parameters when the i.v. dose was increased from 10
`to 40 mg.
`
`Table IV. Some disposition characteristics of omeprazole in man determined from an i.v. dose of 10 mg and 40 mg,
`respectively (MeankSD; n = 10).
`
`Dose
`
`vc
`1 . kg-1
`
`V8
`1 . kg-’
`
`td28
`h
`
`10 mg i.v.
`40 mg i.v.
`
`0.14f0.03
`0.15f0.02
`
`0.34k0.04
`0.37k0.05
`
`0.48f0.04
`0.59f0.08
`
`Plasma
`clearance
`ml . min-I
`
`658f37
`633f42
`
`DRL EXHIBIT 1029 PAGE 14
`
`

`

`92
`Binding to plasma proteins
`The binding of omeprazole to rat, dog, and human
`plasma proteins, human serum albumin (HSA) and
`cY,-acid glucoprotein (a,-AGP) has been studied at
`ambient temperature and at 37 "C by the ultrafiltra-
`tion technique (15).
`Omeprazole in concentrations covering the normal
`range of therapeutic i.v. and oral doses was added to
`fresh plasma, solutions of HSA (Albumin, Kabi;
`purity >95 Yo; 6.8 X W4M) an a,-AGP (Sigma; 0.8
`mgxml-I) in phosphate buffer pH = 7.35, I =
`0.167. Trace amounts of [3H]omeprazole (radio-
`chemical purity 98.4 070) were added to each
`sample, and the concentration of omeprazole in the
`plastic bag and in the ultra-filtrate was determined
`by liquid scintillation counting.
`Omeprazole was bound to about 95.5 070 in the
`human plasma at 20"C, Table V. The degree of
`binding was not affected by a hundred-fold varia-
`tion in the concentration. The binding was less ex-
`tensive in the dog and the rat, in which the average
`binding was close to 90 and 87 070, respectively,
`Table V. Like in the human plasma, the degree of
`binding was constant in the plasma of these animal
`species over the concentration interval studied.
`
`Table V. Binding of omeprazole to human, dog, and rat
`plasma at 20°C. (MeanfSD)
`
`Plasma conc
`prnol.l-'
`
`Per cent bound omeprazcrle
`
`Man
`
`Dog
`
`0.19
`
`1.9
`
`19.4
`
`95.8k0.42
`(n = 7)
`95.7f0.40
`(n=7)
`95.5