E
`
`10
`
`Pharmacoltinetics of Subcutaneous Methotrexate
`
`By Frank M. Balls, Joseph Mirro, Jr, Gregory H. Rearnan, William E. Evans, Cynthia MeCul|y.
`Karen M. Daherty, Robert F. Murphy, Susan laliiries, and David G. Poplaclt
`
`The phorrnacoldneflu al subcutaneously adminis-
`tered rnelholrexole was nurllecl as a palen1erulaI-
`ternative to trail administration. In lulllal lIu5lhtI-
`llysludywasperfonnedlnlhuusmonkeya
`comparing the subcutaneous rattle lo Intravenous
`(IV) Irt|ecllan and oral ndntlnlefrvuflon. The sub-
`cutaneous done was completely absorbed and a
`sustained-release effect was obsenned when com-
`pared with Ilse N date. No local or systemic taxid-
`l-les resulted lrIII'I'I eu_beulaneou.I - in
`the arllrnola. ‘he-elve children with acute lympho-
`Ialaslle leukemia on maintenance therapy protocols
`prescribing "either 7.5 mg/rn’ biweekly orltl rnglrn’
`weeldy were ulna monitored after both a subcuta-
`neous and on oral close "oi melhelrexate. Four chil-
`dren at the higher dosage level were also Ilutlled
`alter on equal N dose. The eubculoneou-I done was
`
`N'I'ERMIT'I'ENT low-dose methotrexate
`has become standard therapy for the mainte-
`nance of remission in children with acute lym-
`phoblastic leukemia (ALL) and is also used as
`an immunosuppressant in the treatment of a
`variety of other conditions, including psoriasis.
`rheumatoid arthritis, and asthma. At doses of 30
`mgfm’ and less, methotrexate is routinely ad-
`ministered by the oral route. However, pharma-
`cokinetic studies have demonstrated that plas-
`ma methotrexate concentrations following oral
`administration are highly variable as a result of
`interpatient differences in the rate and extent of
`absorption.“ In one study, peak levels occurred
`
`
`
`Froni the Prdiaaic Brandt, Namaf Cancer Insrinrre, Be
`lltandfl. MD; St Jude C}u'klr:n'.r Research Hospital, Merrtphiv;
`and Children: Hospital National Medical Center. Wathrhglorr.
`DC.
`Submitted June 1?, 1938; accepted July 25, I988.
`Supported in pan’ int NIH Umm’: Na. CA20.l80 and
`C42} 765. Dr Mirm is a rer.ipien! afa Clinical Oncology Garter
`Developnuru’ Award from the A.-rrer-iron _Ctmc:r Society.
`Address reprirtl mqzram to Frurslt M. Baits, MD. Podium‘:
`Bmncil, NCI. Bldg 10. Room .l'3N2‘40, 9090 Rockville Pike,
`Bethesda, MD 29892.
`Ilulrisa Usgmermnent work. flrerearz noreso-ictianron in
`use.
`0732-ISJXISSIUGIZ-0006$0.00flJ
`
`again completely absorbed in these eltlltlren at
`both ':leeelevele.whereastlo'eeraldoge.whIchpro-
`dueed comparable plasma drug concentrations at
`the leaner dosage level, resulted In a total drug ex-
`posure (area under lhe plasma concentration-tlrne
`curvelrhalwlucue Ihlulflw1ol_rheequ'a|nrburIa-
`neous dose at-the higher dosage level. No local or
`lrelemlc leulelly was attributed to the urbcutoneoiie
`I'IIoIlIo‘I‘I'e.ttole._ Sirbotrlaneotu Ml_lnlrI|lII'Il‘l*|oI'I of
`rrtelltalreeale I: well lolenlfletl and II" ab_aarb"ed
`and appedre lo overootsie the peablerlu auaelnted
`vrlfll oral edntlnlirraflan, Including variable ob-
`sarptlen and url-urutlon at the absorption mecha-
`nism with Increasing doeel.
`J clln Once! 6.-1882-I886. ‘I'M: tr e us yrneminent
`work. Therearenorestflcriomonflsuee.
`
`from 0.5 to five hours after the dose, and the
`fraction of the dose absorbed ranged from 0.23
`to 0.97.’ This variability in plasma drug concen-
`tration may have accounted for the higher re-
`lapse rate seen in one study in which children
`with ALL treated with oral methotreatate were
`compared with those treated intramuscularly.’
`_In addition, rnethotrexate absorption appears to
`be saturable, so that as the dose is increased, the
`fraction absorbed declines.” Therefore, in pa-
`tients with low plasma drug levels, simply in-
`creasing the dose may not overcome poor bio-
`availability.
`The intramuscular route has been the prima-
`ry alternative to oral methotrertate in leukemia
`studies. Intramuscular rnethotrexate is rapidly
`and completely absorbed resulting in higher se-
`rum drug concentrations than following oral
`rnethotrexate.‘-'-“' However, intramuscular in-
`jections must be administered by a health pro-
`fessional and may be difficult in chronically ill
`children with minimal muscle mass. In the pres-
`ent study, the subcutaneous route was evaluated
`as a parenteral alternative to oral administra-
`tion in children with ALL. 'I'_l'1e potential advan-
`tages for this route of administration include
`slow release of drug resulting in more prolonged
`exposure to methotrexate (a critical determi-
`
`1852
`
`Jaurnal of Clinical Oncology, Vol 6. No I! {December}, 1988: pp 1882-1836
`
`Information downloaded from jco.ascapubs.crg
`and provided by UNIV MINNESOTA on May 22. 2003 from 1EE|.94.23?.242.
`Copyright © 1983 by the American Society of Clinical Oncology. All rights reserved.
`
`
`
`MEDAC Exhibit 2020
`
`ANTARES v. MEDAC
`
`IPR2014-01091
`
`Page 00001
`
`MEDAC Exhibit 2020
`ANTARES v. MEDAC
`IPR2014-01091
`Page 00001
`
`

`
`
`
`SUbCUTANEOUS METHOTREXATE PHARMACOKINETICS
`
`1883
`
`pant of cytotoxicity). ease of administration. and-
`less valiable, more complete absorption than
`that observed with oral administration. The fea-
`sibilityof this approach was first studied in Rhe-
`sus monkeys and then in children with ALL at
`two different dose levels.
`
`MATEIUALS mo Mm-loos
`
`Drvs
`Methotrenatewasobtained front commercial sources ("Le-
`derle, Pearl River. NY). The standard _intravenous (IV)
`preparation was used for both the IV doses and sIibuitane-
`ous dosesin the animals and patients, and for the oral doses
`in monkeys. Standard 2.5 "mg tablets were used in patients
`studied with an oral dose.
`
`_
`A':u'mal.r
`Fve adult ma'_le Rhesus monkeys (Mnceeen madam) rang-
`ing in weight from 4.3 to 10.1
`_{media.rl, 8.3 kg) were
`studied: The animals were housed individually and
`water and food Id l_ll3il‘l.Ein (animals were tested overnight
`before the oral dose). Each
`was treated with metho-
`trexate at adnseofl mg"kgbyl.hree routes, orally, subcuta-
`rieously, and “by IV bolus, with the order ol administration
`determined tabdmltly. In addition. tlttee of the animals te-
`ceived a 60-minute infusion of 1 otgfkg of methotrexate;
`given aminimumofzweelratolredoverbefore
`the next dose was administered. Blood samples were drawn
`from a uphenous or femoral venous catheter. ccntralateral
`to the site.of injection in the ease of the IV doses. The
`hepet-lnitetl specimens were obtained betote tltedose and 5,
`15, 30. 45.511. ette9ant1ttuteseu'tt2.3.4, 6, sand 12 hours
`after the dose. Plasma was separated immediately by cen-
`trifugation and frozen at -20°C until assayed.
`
`-Pattern:
`_
`'I\-velve children" (nine titties and three females) with ALL
`in
`being treated on eitheran initial protocol (a =
`6. ttttitttttl Cancer Institute [Not], Qti1then't Hospital Na-
`-tional Medicalflenter) or a relapse protocol (n .— 6. St Jude
`Children's" Research Hospital) participated _in this study.
`The patients _rttng'ed in age from 3 to 19 years (median. 8
`years). Informed consent was obtained from the patients
`and their legal guardians before entry onto the study. All
`pttiientawere in their first or second ren1_1sslon and receiving
`methohjeiate as maintenance therapy on one-,_olt' two sched-
`ules, either 7.5 mgfmz orally. twice a week (:51 patients) or -60
`mslmz orally. once a wee'lt(si1 patients). The siir patients at
`the low-dose level (actual eteen'tl_ote received, as lllj.-'ll'I2)
`were studied following both their standard oral dose and an
`equal dose administered subcutaneously. At the high"-dose
`level. four patients were monitored alter oral, subcutane-
`ous. and IV bolus doses, one patient was studied after only
`an oral dose. and the sixth patient after only a subcutaneous
`dose. The order or administration was deterntlned random-
`I'y. Patients were fasted overnight before the oral dose. Dora-
`plete blood counts. liver function tests, and renal function '
`tests were routinely monitored on these patients heforeand
`
`'1 week a'.fte_r ‘each dose and tienttinstrated normal bone mar-
`row, hepatic. and renal funetion._ I
`__
`‘
`Blood eampleswere collected in heparin.l.a5ed tubes before
`the dose and _l5. 3-0. I50. and 90 tnihutuand .2. 3, 4, 6, and 3
`hours after the dune. Plasma was separated by eentii£uga-
`tien and frozen at —2|J‘C until assayed.
`
`Sample Analysis
`Methotrexate was measured with the‘ dihydrofolate re-
`duetase inhitiition assay which is spcdfie for methotrerate
`ai'td.l'laa a lower limit at setttitsvity or .001 .ttnt'aIl1.."
`
`Phorrrtacoldnetic Caknladons
`Area under the plasma concentration-tilpe curve (ADC)
`was derived using the linear u-spa.-cine! mic and ex‘t1'a'pol.at-
`ed to infinity using the elimination rate constant derived
`stem norllinear regression analysis or the data.” For the Iv
`bolus dose: the methctresate concentration at time 0 used
`in the calculation of the AUC was the sum of the intercepts
`(A + B) derived from fitting the data to the bietlponential
`equation below (using man"):
`
`C(tj-Ae""+Be‘3‘.
`_
`Absolute biosvailability (F) at the 40 _1i1,3.lIu1 dose was
`calculated from the AUC using the fiollowing equation:
`
`F
`
`_ AUc*’° °* 5° - Dose”
`AUCIV - Dme_P° °* 9‘?
`_
`(Abbreviations: 150. oral; SC. subcutaneous}
`cseereeee wet calettlttetl by dividing the ease‘ by the nut:
`
`ltESULTS
`
`_
`
`_
`Animal study
`curves for metho-
`I The plasma
`trexate administered subcutaneously, by W bo-
`lus. and by 60-minute IV infusion are shown in
`Fig 1. The plasma methotrearate concentration _
`following the Subcutaneous dose
`15 to '
`30 minutes after the. dose. and ranged from 1.0
`to 2.3 |.i.lnol.~’L. The‘ sustained-release--efl'eet_
`from subcutaneous adniinistration can be ap-
`preciated from the curves.
`plasma methc't- '
`treitate concentration remained‘ above 0.1
`p.n1ollI_.. two— to three-fold longer with subcuta-
`neous administration than with IV bo_l_u.s or infu— _
`_s'io_n'doses. Plasma concentrations following the
`oral dose are not shown because the absorption
`of methotregtate in these animals was poor
`(<2% of the dose) and was not felt to be at
`representative model for humans.
`_
`_
`Table 1 lists the pharmacokinetic parameters
`for methotrexate administered by the various
`routes. The AUC for the subcutaneous dose ac-
`tually exceeded that for the IV bolus dose in all
`five animals studied. Since the dose was identi-
`
`lrtlorrnation downloaded from jeo.ascopuhs.org and provided by UNIV MINNESOTA on May 22. 2008 from 160.94.23?.242.
`Copyrlght © 1983 by the American Society of Clinical Oncology. All rights roservod.
`
`
`
`Page 00002
`
`Page 00002
`
`

`
`
`
`‘I884
`
`10
`
`..L Q
`
`.9
`
`0.001
`
`0.01
`
`
`
`METHOTHEXATE[MI]
`
`0
`
`2
`
`4
`
`6
`
`B 1012
`
`TIME In]
`H Hg" .1. P|flI_I1l_fl_d.I‘flfl§IlrIgI¢0fllfVIIlOffllO”|0-
`trucrle In Ihecue monkeys fellearlnj administra-
`Iiorl of I rnglltg Irylv bolus [O] (n = 5), do-Irilnute IV
`lnhelon (Inn (at (n = a), and 'euhu_rlon'eeuIl1[EI] to
`= 5}. Polifls and ¢rI'Qr Ianre nopreeenl the geeinetrlc
`mean and one SD. Plume concemretlen of metho-
`treente lellcnelng the subcutaneous due is malai-
`tulned above 0.1 pmel/I. for 6.4 been compared
`Hes.
`nrlfil 2.2 and 3.3 hours tor the IV bolus and Infusion
`
`cal for both routes, this difiference may either be
`due to the more rapid clearance of the IV bolus
`dose or to an underestimation of the time D
`methotrexate concentration from the curve fit-
`
`ting. As a result of this unexpected finding,
`
`BALISETAI.
`
`three animals received a repeat dose of metho-
`trexate infused IV over one hour to more closely
`simulate the levels achieved with the subcutane-
`ous dose. In these three animals the bioavail-
`
`ability of the subcutaneous dose was 102% 1
`12% with the 60-minute infusion is used as the
`standard. There was no local or systemic toxicity
`associated with the subcutaneous injection of
`methotrexate in Rhesus monkeys.
`
`Patient Study
`
`Figure 2 shows the plasma concentration-
`time profiles for subcutaneous methotrexate
`compared with oral administration at the 7.5
`mglm’ dose level (Fig 2A) and compared with
`IV and oral administration at the 40 mglmz dose
`level (Fig 23). At the lower dose level subcuta-
`neous administration approximates the levels
`achieved with the oral dose. However, at the
`higher dose subcutaneous injection results in
`considerably higher plasma drug concentra-
`tions. Peak methotrexate concentration and
`AUC with the subcutaneous dose were four-
`
`than
`respectively,
`higher,
`three-fold
`and
`achieved with an identical oral dose (Table 2),
`and the subcutaneous dose provided exposure
`to a 1 |.l.lIIOIfL concentrations of methctrexate
`for up to six hours compared with 2.6 hours with
`the oral dose. The sustained-release effect with
`subcutaneous administration observed in the
`
`animals was not as evident in these patients
`when compared with the IV dose. Subcutaneous
`methotrexate was rapidly absorbed with the
`
`AUC
`
`Parameter-e_fer_!olet|Ie1nmute
`Table I.
`Administered by Verleul Routes‘ to lltesue fl.nfiHC]I_
`Bioovoilohility
`T‘''‘''
`at sc MTX
`Plasma
`1%’
`Clear-
`-
`once-f
`N In!
`IV Bolus
`"_""°""""’
`_
`waigtn
`Ani-
`IV Inf
`Nlolee
`SC
`(kg)
`mol
`[rnl/Inin]
`Std‘
`Std‘
`2.38
`3.70
`8.5
`68 I P
`4.08
`I03
`9|
`I 18
`I 0?
`-
`I I 9
`2.9?
`3.52
`a 8
`bar?
`92
`I I5
`I I 7
`4.03
`4.?3
`I0:I
`502!‘
`2.52
`2.7?
`4 8
`63IT
`?'0
`-
`I I0
`er
`101
`I45
`4:50
`3.1a
`4.65
`7:5
`am
`4.2?
`3.00
`3.87
`Maori
`93
`I 02
`I 24
`
`
`
`
`
`
`as: 0.43 o.2a I 4 I 2:50 I 6
`
`PO
`.089
`.1 53
`.056
`ND
`.044
`
`4.I2
`
`Abbreviations: IV li'I'I, intrtrverteus irrhrsion; Std, standard; MTX, rntithotrettete; ND, not de-
`tectable.
`'BiocrvniIobiIi1y calculated by dividing AUC3c Hy either AUC" "°'"' or Al.1C"”"‘.
`1-Clearance of the IV bolus dose.
`
`lnfonnation downloaded from jco.ascopubs.org and provided by UNIV MINNESOTA on May 22. 2003 from 160.94.23T.242.
`Copyright © 1983 by the American Society of Clinical Oncology. All fights reserved.
`
`
`
`Page 00003
`
`Page 00003
`
`

`
`
`
`SUBCUTANEOUS MEI1-IOTREXATE PHARMACOKINETICS
`
`1885
`
`ID
`
`l|E'i'ltm'fl‘El.A‘!'Ewt} 2
`
`EDI
`
`IN’!
`
`E
`
`Fl
`
`3
`
`UIZIIOOTB
`‘l'lHE|_‘h|
`
`ID
`
`tmuornntamwit 9
`
`0.01
`
`Em!
`
`disappear-
`Fig 2. Plasma
`ance curves In methetreztnle In
`children with ALI. following ud-
`rrtlrtlslretlen of (it) 7.5 raglan’
`orally [A]: and sub-elrtoneouely
`{Cl} to II: puIier|'II; and {B} #0
`molar‘ W (Cl 0''
`’—‘ 4): ON"! (Al in
`= :g. and euhetrlrlrleeluly {Cl} {rt
`
`012343!!!
`73305]
`
`peak concentration occurring between 15 and
`30 minutes.
`
`Pertinent pharmaooltinetic parameters are
`listed in Table 2. The peak plasma concentra-
`tion and bioavaiiability at the lower dose are
`equivalent for oral and subcutaneous metho-
`trexate, but the clear advantage for the subcuta-
`neous dose at the 40 mglnf level can again be
`appreciated. The subcutaneous dose was com-
`pletely absorbed, whereas, only 42% of the oral
`dose is bioavailable. The advantage for subcuta-
`neous administration can also be appreciated by
`comparing the relative bioavailability of the sub-
`cutaneous and oral 4-ll mg/tn‘ doses using the
`lower dose as a standard. The relative bioava.ila—
`
`bility of the subcutaneous dose is 106% com-
`pared with 43% for the oral dose. When injected
`slowly, subcutaneous administration of metho-
`trexate was well tolerated in these children
`with ALL, with no evidence of local or systemic
`toxicity.
`
`DISCUSSION
`
`patients on an intermittent schedule (most
`maintenance regimens for ALL include weekly
`oral methotreitate at a dose of 15 to 20 rngfrn').
`Subcutaneous methotrexate was rapidly and
`completely absorbed at both dose levels studied,
`without evidence of local toxicity at the injection
`site.
`
`The finding of a greater AUC for tttethotrex-
`are following subcutaneous administration com-
`pared with that resulting front an equal dose
`administered by IV bolus has two possible ex-
`planations. Total plasma clearance could be
`more rapid after the IV bolus. One could specu-
`late that renal tubular reabsorption is saturated
`at the initial high plasma methotrexate concen-
`trations or that the rapid injection does not al-
`low time for the complete tissue distribution
`and therefore less drug is available for slow re-
`lease at later time points. A more likely explana-
`tion is that the methods used to calculate the
`initial concentration (at time 0) underestimated
`that value leading to an underestimation of the
`AUC for the IV bolus dose.
`
`The results of this study indicate that the sub-
`cutaneous route appears to be a feasible route
`of administration for low-dose methotrexate in
`
`Figure 3 illustrates the advantage for subcuta-
`neous methotrettate over oral administration as
`
`the dose is increased. The AUC for a variety of
`
`Table 3. Phunnueoklnetie Parameters for Methoflillte Administered
`by Various lorries and at ‘I've Dose Lovell to Cltllrlrerl Willi All
`AUC
`Peolt Cons.
`Bioovniinbili-iy
`
`‘WM’ . _"‘='___
`PO
`Iv
`sc
`PO
`N
`sc
`P0
`sc
`2 .99
`~
`0.94
`0.95
`—
`—
`-
`3.3a-
`= 1.34
`:t:I.28
`: 0.46
`3 L65
`tr-=6}
`tn=6l
`tr-=61
`("=61
`42
`126
`11.4
`2o.o
`r.93
`1.40
`1.73
`22.0
`:15
`:60
`12.5
`sun :15
`:3.00 was
`:9.o
`
`
`ln=4lln=5lln=5l in=4l in-=5) ln=5l ln=-4! tr-=4}
`
`
`
`
`
`‘Data presented is the moon 1 one SD.
`
`40
`
`lnfonnation downloaded from jco.ascopubs.org and provided by UNlV_M|NNESOTA on llliay 22. 2008 from 1fiO.94.23?.2at2.
`Copyn'gi1l© 1988 by the American Society oi Clinical Oncology. All nghls reserved.
`
`Page 00004
`
`
`
`om
`{mg/m7)
`7.5
`
`Page 00004
`
`

`
`
`
`'l 886
`
`24
`
`AUGDIM-hr] B6:‘
`
`
`
`0
`
`‘I0
`
`20
`
`30
`
`40
`
`50
`
`60
`
`DOSE [rnglrnzl
`Hg 3. Relationship between the mean NJC and
`subcutaneous dose adnslnlarrutlon (El) at low and
`high level: compared with oral adrrtlrlltlratlen (O)
`at various dose levels. Date from the present study
`and all-|era"aro lrIeludod.'l'lro nurllhornelflu each
`poln-I is the nu minor 01' data points averaged in yield
`the point. The oral dose AIJC plateau indicates salu-
`railort of the absorptive mechanism.
`
`oral doses both from this study and several other
`published reports”-"-" is shown relative to the
`dose administered. At doses of oral rnethotreic
`are of 30 rnglmz and above, the AUC plateaus,
`presumably as a result of saturation of the ab-
`
`BALIS ETAL
`
`sorption process. This saturation of absorption,
`which has been previously described for orally
`administered rnethotrexatef-‘*9 was not ob-
`served with the subcutaneous dose.
`Because of its substantially better absorption
`at doses >20 mg/mi, subcutaneous administra-
`tion appears to have a pharmacolrinetic advan-
`tage over oral dosing in this dosage range. This
`bioavailability difference with increasing dose
`has also been recently observed in a study com-
`paring intramuscular and oral administration.‘
`In this study the intramuscular dose was com-
`pletely absorbed over a dosage range of 13 to 76
`mgfm‘, whereas the percent of the oral dose
`absorbed fell from 42% at doses of s 40 mg.-‘mi
`to 18% at dose >40 mglm’.
`Subcutaneous methotrexate may also be of
`use in selected patients on doses <20 mg/tn‘
`who absorb the drug poorly from the gastroin-
`testinal
`(GI) tract.“ Considering published
`data from one study on the superiority of paren-
`teral (IM) methotrexate in maintaining remis-
`sions in ALL.’ a case could also be made for
`using intramuscular or subcutaneous metho-
`trexate during maintenance therapy in all chil-
`dren with ALL. Although not studied here, the
`subcutaneous route may also be useful for long-
`term, low-dose continuous infusion of metho-
`trexate.
`
`REFERENCES
`
`1. Kearney PJ. light PA, Preeoe A, et al: Unpredictable
`serum levels after oral methotrexate in children with acute
`lymphoblastic leukaemia. Cancer Chemother Pltarmacol
`3:11?-120, 1919
`2. Balls FM. Savitch IL, Bleyer WA: Pharmacokinetics of
`oral methotrexate in children. Cancer Res 43:23-t2-2345,
`1933
`3. Pinkerton CR, Welshman SG. Kelly.lG. et al: Pharma-
`coltinetics of lowdose methotrexate in children receiving
`maintenance therapy for acute lyrnphoblastic leukemia.
`Cancer Chemother Pliarmacol 10:36-39. 1932
`4. Pinkerton CR, Welshman SG, Bridges.l'M: Serum pm-
`files of methotrexate after its administration in children with
`acute lymphoblastic leukemia. Br J Cancer 45300-303.1932
`5. The Medical Research Council's Working Party on
`Leuliaelnia in Childhood: Medical Research Council leu-
`kaemia trial. UKAIJ. VII. Arch Dis Child 60:l05[l-1054,
`1935
`6. Henderson ES, Adams-on Rl-I. Oliver-in VT: The meta-
`bolic fate of tritiated methotrexate ll: Absorption and excre-
`tion in man. Cancer Res 2S:l0l8-1024. 1965
`‘J. Campbell MA, Perrier DG. Dnrr RT, et al: Methotre:t-
`ate: Bioavailabiliry and phannaeokinetics. Cancer Treat
`Rep 69:833-838. 1985
`
`3. Smith DK. Ornura GA, Ostroy F: Clinical pharmacol-
`ogy of intermediate-dose oral methouerate. Cancer Che-
`motlter Phsrrnaool 4:11’?-120, 1930
`9. Tereai ME, Crom WR. Cltoi KE. et al: Melhotrexate
`bioavailability after oral and intramuscular administration
`in children. J Pediatr 1101738-192. I931
`10. Freeman-Narrod M. Gerstley Bl. Enptrom PF. el al:
`Comparison of serum concentrations cl’ rnethotzreitate after
`various routes of administration. Cancer 3-6:161?-l62-1, 1975
`ll. Fallt DC. Clark DR. Kalman SM. et al: Enzymatic
`assay for methotrexale in serum and cerebrospinnl fluid.
`Clin Chem 22:185-788. 1916
`11'. Gihaldi M, Perrier D: Pharrnaeokinetics (ed 2). New
`York. Deldter. 1982. pp 445-449
`13. Knoll. GD: MLAB—A mathematical modeling tool.
`Comput Programs Biomed 10:261-230. 1979
`14. Stuart IFB. Calman KC. Waiters J. et al: Bioavailabil-
`ity of methotreatate: Implications for clinical use. Cancer
`Chernolher Pharrnacol 3:239-ll-ll. 1979
`15. Steele W1-l. Stuart JFB. lanvrence JR. el al: Enhance-
`ment of methotrexate absorption by subdivision of dose.
`Cancer Chemother Pharmacol 3235-237. 1919
`
`Information downloaded from ]co.ascopubs.org and provided by UNIV MINNESOTA on May 22. 2003 from 160.94.23?.242.
`Copyright © 190-B by the American Society of Clinical Oncology. All rights reserved.
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