.- : . .. ',. . .,
`
`Pharmaceutical Reuan.·ll. Vol. 16. Nu. 7. 1999
`
`Researcf1 Paper
`
`Regional Differences in Quinine
`Absorption from the Undisturbed
`Human Colon Assessed Using a Timed
`Release Delivery System
`
`distal sites ( 1,2), but in normal clinical use colonic contents
`may have an important modifying effect. We therefore aimed to
`study absorption by measuring the permeation of probe marker
`molecules from different regions of the distal gut, using a
`delivery system, the Pulsincap'" (3}, which allowed selective
`delivery to various regions of the undisturbed gut.
`
`METHODS
`
`Subjects
`
`Thirty-nine healthy volunteers (23 male; 16 females), age
`rdnge 20-40, were recruited into the study. All subjects were
`free from gastrointestinal disea'iC, and were not taking any
`laxatives or drugs known to affect gut motility. All were asked
`to refrain from eJtccss alcohol, cunies, and aspirin or non(cid:173)
`steroidal antiinOammatory drugs during the course of the study.
`Females were required to have a negative pregnancy t.est on
`the morning of the study day. The study was approved by
`Nottingham University Ethical Committee and the Association
`of Radioactive Substances Advisory Committee at the Depart(cid:173)
`ment of Health.
`
`Study Protocol
`
`Plrase I
`In the initial phase of the study, II healthy volunteers (6
`males; 5 females; age range 20-29) were recruited into a two
`way crossover study in which ttcey were dosed with either a 5
`hour (pan A) or 15 hour (part B) release delivery capsule
`in an auempt to selectively target permeability probes to the
`proximal colon or distal colon respectively. There was a 2 week
`washout period, and the volunteers were required to adhere to
`a 20 gm fibre diet for 2 days before each of the study days. In
`part A, subjects ingested the 5 hour release delivery system at
`0800 h following an overnight fast, and then consumed a stan(cid:173)
`dard 200 kcal breakfast of toa~t. buller and jam once the capsule
`· was seen to empty from the stomach. A standard 600 kcallunch
`and 1000 kcal meal were provided at 1300 h and 1800 h
`respectively. Blood samples were taken prior to, and at 30
`minute intervals after the predicted release time ( 1300 h), and
`urine was collected in the 3 hour period leading up to the
`expected release time, and for the 0-20 hour period following
`the eJtpected relea~e time. In pan B. subjects were dosed at
`2200 h on the evening prior to the study day, so that the predicted
`time of release would be the same a-: in pan A (i.e .• 1300 hrs).
`An identical meal pattern, blood and urine sampling protocol
`wa.~ followed.
`
`Plwse 2
`
`This comprised 12 healthy volunteers who were dosed on
`a seplirate occasion with a 5 hr release Pulsincap"', and 16
`healthy volunteers who were dosed with a 6 hr release Pulsin(cid:173)
`cap"'. These28 healthy volunteers (17M; II F. age rangc20-40)
`followed an identical protocol to phase I part A.
`
`Pulsincap '" Delivery Capsule
`
`The Pulsincap 'M delivery capsule consists of a waler insol(cid:173)
`uble body with a hydrogel plug in.<;erted at its open end, which
`
`John M. Hebden, 1 Clive G. Wilson,2
` Peter J. Gilchrist,2
`Robin C. Spillcr,1
`Elaine Blackshaw,l Malcolm E. Fricr,J and
`Alan C. Perkinsl
`
`•4
`
`Received Man:il II. /999; acce{Ued A{•ril 12. 1999
`
`Purpose. To investigate the regional absorption chnr:~cteristics of' the
`dist:ll gut us.ing two markm> of penneability, quinine (a transc:cllular
`probe) and 51CrEDTA (a pnraccllulnr probe).
`Methods. The permeability markers were delivered to the undisturbed
`gastrointestinal tract in 39 healthy volunteers using an oral timed(cid:173)
`release delivery vehicle which allowed pulsed release within a pani~-u­
`lar site of the gut Site of release was identified using gamma scintigra(cid:173)
`phy. Absorplion of quinine and $
`1CrEDTA was assessed by measuring
`the: percent excretion in the urine using tiPLC and gamma counting
`respectively. Serial plasma samples allowed time-con~-cntration curves
`for quinine to be plolled.
`Results. There was a significant trend for diminished absorption with
`more dist:ll delivery of the transcellular probe, quinine, which was:
`6.26 = 0.87% (small intestine. n = 10); 4.65 = 0.93% (ascending
`colon. n = 16); and 2.59 :!: 0.52% (transverse colon, n = 10) of the
`inges~ed dose eJtcrCicd respectively (p < 0.00 I). No such gradient wa.~
`seen with the paracellular marker. s•crEDTA.
`Conclusions. These results suggest that delayed release formuations
`~houd aim for release in the distal small bowel and proximal colon if
`absOlption is to be miximised. Absorption by the transccllular route
`diminishes in the more distal colon, a fact which has implications for
`delayed or sustained release formulations.
`KEY WORDS: transcellular; pnraccllulnr;
`trointestinal.
`
`abwrption;
`
`gll.~­
`
`INTRODUCTION
`
`II has long been the aim of the pharmaceutical industry
`to achieve delayed absorption of drug to treat nocturnal and
`early morning exacerbations of disease, e.g., a-:thma, rheuma(cid:173)
`toid disease, and cardiova~cular disease. Such formulations
`taken at bedtime are inevitably situated in the distal small bowel
`or proJtimal colon by the early hours of the morning. Knowledge
`of the effect of ~ite of release on absorption cha.ractcristics in
`the undisturbed colon is therefore highly relevant in designing
`such preparations.
`Previous studie.~ using a cleansed colon have suggested
`little intrinsic difference in absorption between proximal and
`
`1 Division of Gastroenterology. University Hospital Nouingham, Not(cid:173)
`tingham. UK.
`1 Depanment of Phnrmoceutic31 Science.~. University of Strathclyde,
`Glasgow, UK.
`) Department of Medical Physics, University Hospital Nottingham,
`Nottingham. UK.
`• To whom correspondence should be addre~d.
`
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`swells on contact with water and gradually propels itself from
`the body, thereby allowing the contents to be released. The
`time of release of the plug is dependent on it~ dimensions.
`Each delivery system in this study contained 50 mg of quinine
`hydrochloride. 1.8MBq CrEDTA dried onto sucrose. I MBq
`Indium-labelled amberlite resin as an imaging agent. and an
`excipient. A 50 mg dose of quinine was chosen as this was
`sufficient to be easily detected given the highly sensitive HPLC
`method employed, and low enough as to be unlikely to cause
`any significant side-effect~. The usual dinical dose for treatment
`of muscular cramps is 300 mg once daily and for the treatment
`of malaria 600 mg every 8 hours, but these doses may be
`associated with significant side-effects such as nausea. tinnitus,
`and cardiotoxicity.
`
`Scintigraphic lmoging
`
`Scintigraphic images were ohtained using a GEC Maxi(cid:173)
`camera set with a 20% window for simultaneous acquisition
`of the 140-kcV radiation peak ufTc and the 247-keV radiation
`peak of ln. Anterior and posterior images of 30 seconds duration
`were taken every 30 minutes after dosing. All images were
`stored for later analysis using a dedicated computer. Alignment
`of serial images was facilitated by taping small radiolabelled
`markers (0.2 MBq of Tc} anteriorly and posteriorly over the
`hepatic area. The position within the gastrointestinal tract, and
`the time of rclea.o;e of markers from the delivery system was
`determined by vi~lJal inspection of the serial images. Release
`could easily be Inferred from the serial images as tht: area of
`the hot spot increased and its intensity concomitantly decreased.
`
`Quantification of Marker Probes
`
`The analysis of quinine was carried out using an e.~ab·
`lished reversed-phase HPLC method (4). The HPLC apparatus
`(HP 1050) wa.~ fitted with an auto sampler and a nuorescence
`detector. For the assay of quinine optimum settings were: excita·
`tion = 350 nm, and emission wavelength = 450 Jlm. The
`mobile pha.~c consisted of an acetonitrile-aqueous phosphate
`buffer (10 mM) mixture (70130 v:v), containing 3 mM tetra(cid:173)
`butylammonium bromide (TBA) and 20 mM sodium dodecyl
`sulphate (SDS), pH 2.5. The stationary phase consisted of a
`Hypersil C-18 column (5 mm) 150 X 3.2 mm protected by a
`guard column 30 X 3.2 mm (PhenomeneJt).
`A protdn precipitation technique wa.~ employed in the
`preparation of the urine samples. To 200 J.LI of sample. methanol
`(400 J.LI) was added, the mixture vortcxcd and then centrifuged
`at 1800 g for 15 minutes to remove the precipitate. The superna(cid:173)
`tant was transferred to a siliconiscd glass vial prinr to injection
`from autosampler. Sample injection volume was 10 p..l and
`now rate was 0.5 J.LVmin. Chromatographic scpamtions were
`performed at room temperature. The inter- aml intra- assay
`coefficients of variation were found to be les.~ than 4%. The
`lowest limit of detection for quinine in plasma was 3.5 ng/ml.
`A 10 ml sample of urine was counted in a gamma-counter
`(LKB Wallac 1280) for determination of Cr-EDTA content.
`Reference standard solutions of Cr-EDTA were prepared at the
`beginning of the trials for the calculation of decay corrections.
`After correcting for the total volume of urine in each time
`inrerval, the results were expressed as the % of administered
`dose excreted.
`
`·;:..
`
`Hebden et al.
`
`Thhle 1. Number. Release Time. and Site of Releasc of the S and 6
`Hour Pulsincap Delivery Systems
`
`5hr Pulsincap
`
`6hr Pulsincap
`
`Number
`Release
`Site
`
`16
`23
`7.3 :!: 0.3 h
`S.S ~ 0.2 h
`Sl 5
`SIS
`AC 5
`AC II
`TC6
`TC 4
`Note: Sl = small intestine: AC = ascending colon; TC = transverse
`colon.
`
`Statistics
`
`Permeation of the marker probes from the different sites
`was analysed using one way analysis of variance (ANOVA).
`and Jonckhccre's test for ordered alternatives.
`
`RJo:SULTS
`
`The site and times of delivery are summarised in Table I (5
`and 6 hr delivery systems) and Table 2 ( 15 hr delivery systems).
`In 20 out of the 23 subjects ingesting the 5 hr release
`system, scintigraphic release occurred in the distal small bowel
`or colon. In one subject, the delivery system lay in the rectosig(cid:173)
`moid colon and did not appear to release, and in two subjects
`the delivery syste m wa.<; retained in tlte stomach and therefore
`released in this region. Release occurred successfully in the
`distal small bowel or colon in all of the 16 subjects ingesting
`the 6 hr relea'ie delivery system.
`In the II studies involving the 15 hr release delivery
`system, scintigraphic release was only observed in 2 subjectl'
`(in the a<>eending and transversi! coloos at 19.4 and 20.5 hou r~
`artcr ingestion). At the predicted release time, 9 of the I I
`de livery systems resided in the colon (2 had been excreted).
`The majority of the systems, however, were located in the
`proximal colon (rather than the intended distal colon).
`Since release of probe marker was by and large unsucces.~­
`ful using the 15 hr release delivery systems, we have restricted
`our analysis to the 5 and 6 hr release data. We were thus able
`to compare delivery of marker probes to the small intestine
`(n = 10), ascending colon (n = 16), and transverse colon (n
`= 10).
`
`1't~hle 2. Number, and Site at Expected Release lime of the IS Hour
`Pulsincap Delivery Systems
`
`I 5hr Pulsinc:~p
`
`Number
`Release
`Site
`
`11
`n/a
`Sl
`AC
`TC
`DC
`excr
`
`0
`6
`I
`2
`2
`
`Nme: Release time is not :tpplicable (nl~t) as only 2 were evidenced
`to release scintigraphically. (SI = small intestine; AC = asc~:~~ding
`colon: TC = transve~e colon).
`
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`Regional Differtnces in Colonic Absorption of Quinine
`
`Scintigraphic release was seen a liule earlier in those imli(cid:173)
`viduals with delivery to the small intestine compared to the
`ascending and trarnsvcrsc colons (small intestine 5.7 !: 0.4 hrs;
`ascending colon 6.0 !: 0.2 hrs; transverse colon 7.3 !: 0.5 hrs).
`resulting in a slightly grea!Cr time for pcnncation to occur.
`Excretion of all or a proportion of the released iS04opc
`had occurred in balf of the subjects by the end of the 0-20 hr
`urine collection period. with approximately equal proportions
`in each set of individuals grouped by initial release site (small
`intestine 5110; ascending colon 7116; transverse colon 6/10).
`
`Permeation of Marker Probes
`
`Quinine absorption diminished with progressively more
`distal release of capsular contents. as assessed by the 0-20 hr
`urine collection: small intestinal release. 6.26 ± 0.87% of the
`ingested dose excreted; ascending colon release. 4.65!: 0.?3%
`of the ingested dose excreted; and transverse colon release.
`2.59 ± 0.52% of the ingested dose excreted (Fig. I). Ooc way
`analysis of variance showed a difference between these sites.
`with Jonckheere's test for ordered alternatives showing a signifi(cid:173)
`cant trend for decreased absorption with progressively more
`distal delivery (p < 0.001). Pem~eation of EDTA, however.
`showed no such gradient: small intestinal release, 1.43 ± 0.43%
`of the ingested dose excreted; ascending colon release, 0.60 !:
`0.18% of the ingested dose excreted; and transverse colon.
`1.17 :!: 0.64% of the ingested dose excreted (Fig. 2).
`Although time concentration proliles of plasma quinine
`seemed to show a trend for a more rapid upstroke with more
`proximal delivery (median (range) times to peak concemration:
`small intestine 1.9 (0. 5-3.31 hours, ascending colon 2.3 {0.6-
`171 hours. transverse colon 2.5 (1.0- 8.01 hrs), this wa.~ not
`~lalil'tically signific;tnt. There was however a significant trend
`for greater peak concentrations with more proximal delivery
`(median (range! concentration: small intestine 0.66(0.13- 1.061.
`ascending colon 0.38 {0.02-0.611. transverse colon 0.18 [0.011-
`0.601. p < 0.005, Jonekhecre's test for ordered alternative.~. sec
`Fig. 3).
`
`DISCUSSION
`
`The Pulsincap"' delivery system allowed us the opportu·
`niry lo examine rhe absorption characteristics of the colon in
`
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`7
`
`6
`s
`
`'l.EOTA
`recovered 4
`in urine
`
`3
`
`2
`
`0
`
`0
`
`0
`
`6
`
`0
`
`AC
`TC
`Sl
`loig. 1. Percent of ''CrEOTA appearing in the urine following rei=
`in the distal small bowel (SI), ascending colon (AC), and uansvenc
`colon (TC).
`
`a non-invasive physiological manner, hy delivering a bolus
`quantity of marker probe to a selected region. A previous study
`had suggested that a 5 hour release time would allow successful
`targeting of the proximal colon (5).
`The present study shows that precise targeting was not
`possible due to interindividual differences in gastrointestinal
`transit rates. Indeed, despite the reasonably precise release times
`obtained from the 5 and 6 hour Pulsineaps ••. delivery occurred
`in the small intestine in almost l/3rd of cases. and a~ far distally
`as the transverse colon in another l/3rd. Nevertheless. selective
`release in the ilcocaccal region (distal small bowel or ascending
`colon) occurred in 26139 (67%) individuals (using timed 5 and
`6 hour delivery systems. This compares with a ligure or 86%
`in a study employing a methylacrylate ('Eudragit') coating to
`protect gelatin capsules against disintegration within the stom(cid:173)
`ach in 14 subjects (6).
`Selective delivery to the distal colon represented a more
`difficult challenge. The descending and sigmoid colon have
`thick mu!>cular wall!> (7) designed primarily ror propulsion, and
`recent studies have suggested that this region serves as a conduit.
`in contrast to the storage role of the more proximal colon (6.S).
`
`IS
`
`10
`
`5
`
`%Quinine
`recovered
`in urine
`
`0
`
`0
`
`0
`1t
`8
`0
`
`0
`
`0
`
`0
`
`0 t 0 t 8
`
`0~----~----~--~~--~
`Sl
`AC
`TC
`Fig. l. Percent of quinine appearing in the urine following release In
`the distal ~moll bowel (51). ascending colon (AC), and trnnsv~
`colon (TC).
`
`plasma
`quinine
`(pg/ml)
`
`0
`
`10
`time (hours)
`"'ir:. 3. Graph showing the mean concentration of quinine in plasma
`vcfSus time. following slll311 intestinal n:lease (circles), o.~ending colon
`release (triongles). and transverse colon release (squ~~n:s). StAndard
`error b;u-s are shown.
`
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`1090
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`Hebden tt aL
`
`Thus there is likely to be a much smaller 'window' of time
`available for release to result in effective targeting of this region.
`Additionally, as residence time in the a~cending colon has been
`shown to be approximately 12 hours•(9), a substantial delay in
`release time would be required. In vitm work had shown the
`Pulsincap '"delivery system successfully releasing after a delay
`of up to 15 hours. and it was therefore this configuration which
`was used to effect selective delivery to the distal colon.
`Our attempts to target permeability probes to the distal
`colon using the 15 hour delivery system were however unsuc(cid:173)
`cessful on two counts. Firs1 and uneli.J)l.'Ctcdly, the majority of
`the delivery systems were situated in the proll.imal colon at
`their predicted release time (15 hours), and no more further
`advanced when compared to the 5 hour systems viewed 6 hours
`after dosing (Fig. 4). This relative stagnation may in part be
`cll.plained by the different dosing times in the two arms of the
`study. In the 15 hour am1, subjects were dosed .at 2200 hrs so
`that the predicted release time ( 1300 hrs) would be identical
`
`(a)
`
`(b)
`
`..
`
`Fig. 4. Postion of (II) IS hour timed· rclea.w delivery systems within
`the colon IS hours after ingestion, and {b) 5 hour timed-relense systems
`(or relcnsed contents) 6 hours-a flu ingesrion. The c.lisllibution is remark·
`ably similar despite the differing lengths of time post ingestion.
`
`to the 5 hour ann of the study. and therefore meal patterns
`would be the same. Thus in this arm of the study, subjects
`would have slept for approximately 8 or the 15 hours, and sleep
`has been shown to reduce colonic electrical and contractile
`activity (10-14). Delayed nocturnal gastric emptying (15) and
`reduced propagation velocity of the intestinal migrating motor
`complex {16) may also have been contributory, as supported
`by the finding that in 2 individuals the delivery system did
`not enter the colon until 12.5 and 13.5 hours after ingestion.
`Secondly. altllough reliable release from a IS hour release Pul(cid:173)
`sincap"' had been demonstrated in simulated intestinal content'>
`in vitro. there had been no previous in vivo experience with
`this configuration. In fact, scintigrnphic release was only evident
`in 2ofthe 11 volunteers in phase I of the study (altllough plasma
`samples showed evidence of release in a further 3 individuals).
`Targeted delivery to the distal colon using the 15 hour
`delivery capsule was unsuccessful for two reasons. Firstly, the
`capsule.-; were no further advanced 15 hours after ingestion than
`the 5 hour capsules viewed 6 hours after dosing (Fig. 4). This
`was probably related to the period of sleep following dosing,
`which is known to reduce colonic electrical and contractile
`activity (I 0-14 ). delay gastric emptying ( 15). and reduce the
`propagation velocity of tile intestinal migrating motor complex
`(16). Secondly, relea~ was only successful in 5 individuals (2
`scintigrnphically; 3 additionally on plasma measurements of
`quinine). Despite the.<>e shortcomings, we were still able to
`compare regional absorption characteristics of the distal gut as
`a result of the interindividual variations in transit of the 5 and
`6 hour delivery systems, which led to a spread of initial release
`sites. Our results show a clear trend for reduced absorption of
`quinine as one moves aborally from the distal small bowel to
`the transverse colon. A similar gradient however was not
`observed for the pcnneation of CrEDTA.
`Intestinal permeability tests investigate the unmediatcd
`diffusion across the intestinal epithelium of medium and large
`sized, inert, non-metabolised. water soluble molecules. There
`are two main pathways: transccllular and paro~ccllular. The for(cid:173)
`mer arc thought to be small aqueous 'pores' (<0.4-0.7 nm)
`of high incidence, whereas the latter are thought to be larger
`aqueous 'channels' (>6.5 nm) of low incidence allowing the
`permeation of larger molecules such as CrEDTA ( 17 ,18). Lipid
`soluble substances can diffuse directly through the cell surface
`membrane. Monosaccharides. such as L-mamnose (molecular
`mass 164 Daltons; molecular diameter = 0.83 nm) and !>(cid:173)
`mannitol (molecular mass = 182 Dallons; molecular diameter =
`0.67 nm) are
`to permeate
`thought
`largely
`transccllularly.
`whereas disaccharidcs, such as lactulose (molecular mass = 342
`Daltons; molecular diameter = 0.95 nm) and the rndioligand
`51CrEDTA (molecular mass= 359 Daltons; molecular diame(cid:173)
`ter = 1.05 nm) arc thought to permeate paracellularly. The
`relative abundance of the small transccllular pores results ir:
`greater permeation of the monosaccharides (11-19% L·mam·
`nose excreted 5 hrs after oral dosing) compared to the disaccha·
`rides (0.3-0.4% lactulose eltcrcted S hrs after oral dosing)
`(18,19).
`The permeability markers chosen in our study were quinine
`hydrochloride and Cr-51 EDTA. These materials were used
`because of ease of detection and lack of pharmaceutical action.
`The absorption of orally dosed quinine salts occurs rapidly
`witllin around 2 hours, with a bioavailability or 76-88%
`( 19,20.21 ). Quinine hydrochloride is very soluble in both water
`
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`Regional Differences in Colonic Absorption of Quinine
`
`1091
`
`and lipid (I gram dissolves in 16 mls water, I ml chloroform.
`and in 350 mls ether). Quinine ha.~ pKa's of 4.2 and 8.8 and
`is therefore partially ionised in the small and large bowel.
`where pH ranges from 5.5 to 7.8. Since the log P of quinine
`is approximately 2.1. at pH 6.7 il will be equally partitioned
`between water and lipid. It is therefore likely to partition both
`through the lipid membrane and equally through small water
`soluble pores within the membrane (i.e., transcellularly). lis
`appearance within erythrocytes (20) is consistent with these
`concepts. Generally. it is representative of many classes of
`pharmacological compounds which arc absorbed through the
`transcellular pathway. Cr-5 1 EDTA is a large chelate (molecular
`mass = 359 Dalton.~) carrying a small negative charge. and is
`thought to permeate via the paracellular pathway. II adopts a
`strictly extracellular distribution when given intravenously. and
`is therefore thought to be unable to pa.~s through cell membranes
`(ie transcellularly).
`There arc several possible explanations for the gradient
`observed with quinine. Firstly. the fn.-qucncy of aqueous pores
`may be different between cells in different parts of the gastroin·
`testinal tract. Secondly. the mucous layer in the colon limits
`access to the absorptive surface. and this layer has been shown to
`become progressively thicker distally (22). Finally and perhaps
`most importantly, the luminal contents differ between the proxi·
`mal and distal colon. The right side of the colon conta.ins liquid
`stool which would be predicted to promote drug dispersion,
`diffusion and mucosal contact whereas the lcfl side of the
`colon contains viscous. dehydrated stool within which drug
`may become seque.~tercd,.and hence unavailable for permeation.
`An earlier pilot study involving 10 subjects had suggested
`decreased absorption of CrEDTA with more distal colonic
`n:lease(23). We found no such gradient when a larger number of
`subjects were studied (n = 36).11 is possible that the preliminary
`study suffered from a type I error, a.~ the numbers in each
`region were small (small intestine 4, a.~nding colon 3. trans·
`verse colon 3). It is however noteworthy that scverdl EDTA
`absorption values seen in the larger study were much higher
`than expected. The usual upper limit of absorption of CrEDTA
`f<lllowing ingestion as a solution is around 2.6%' (24). and
`several EDTA absorption values seen in this study far exceed
`this figure. One explanation of the abnormally high values seen
`of these re.<;ull~· is that pulsed delivery of sucrose and CrEDli\
`may result in high local concentrations which alter local perme(cid:173)
`ability at the site of release, and hence confound any true
`differences in absorp«ion by region.
`In summary, this study has shown the feasibility of selec·
`lively targeting material to the ileo-colonic region using the
`Pulsincap'" timed release delivery system. Selectively targeting
`material to the distal colon presents panicular difficulties due
`to a combination of temporal factors, interindividual variability
`in transit rates. and the reservoir function of the intervening
`proximal colon. Using the 5 and 6 hour timed release delivery
`systems to target the distal gastrointestinal tract, we have shown
`a gradient of absorption for the transeellular probe quinine.
`Whether this gradient is primarily determined by differences
`in the water content of the stool or properties of the mucosa(cid:173)
`mucus barrier remains to be determined.
`
`ACKNOWLEDGMENTS
`The authors thank Scherer DDS •. Ciydebank, Scotland for
`supply uf the Pulsincap"' timed release delivery system, and
`
`to Dr Harry Seager and Dr Julie Binns for their contributions
`to the project. The work was funded as pan of an MRC (Medical
`Research Council) Link Project with Scherer DDS.
`Clydcbank, Scotland.
`
`REFERENCES
`
`7.
`
`I. K. H. Antonin, P. Bicck, M. Scheurlen, M. Jedrychowski, and H.
`Malchow. Oltprcnolol absorption in mnn after single bolus dosing
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