Analytical Profiles of Drug Substances, 7
`
`EPINEPHRINE
`
`Dale H. Szulczewski and Wen-hai Hong
`
`193
`
`Copyright © 1978 by Academic Press. Inc.
`All rights of reproduction in any Conn reserved.
`IS BN ~12-260801-0
`
`ADAMIS EXHIBIT 1016
`Page 193
`
`

`

`194
`
`DALE H. SZULCZEWSKJ AND WEN-HAI HONG
`
`CONTENTS
`
`1. General Information
`1.1 Nomenclature
`1 . 11 Chemical Names
`1.12 Generic Name
`l . 13 Trade Names
`1 . 2 Formula
`1.21 Empirical
`1 . 22 Structural and Stereochemical
`1.3 Molecular Weight
`1 . 31 Free Base
`1. 32 Bitartrate
`1.4 Elemental Composition (base)
`1.5 Description
`1. 6 Forms of Epinephrine Recognized in Official Compendia
`2. Physical Properties
`2 . 1 Associated with the Solid State
`2.11 Crystallinit y
`2.12 X- ray Diffraction
`2 . 13 Melting Point
`2 . 2 Solubility
`2.3 Spectral
`2.31 Ultraviolet
`2 . 32 Infr ared
`2.33 Mass
`2.34 Optical Rotation and Dispersion
`2 . 35 NMR
`2 . 4 Distribution
`Ionization in Aqueous Solution
`3.
`4. Biochemical Considerations
`5. Synthesis
`6. Stability and Behavioral Chemistry
`6.1 Solid State
`6.2 Aqueous Solut ions
`6.21 Racemi zation
`6.22 Reaction with BisuJ.fite
`6.23 Oxidation
`6.24 Miscellaneous Reactions
`6.25 .Dosage Form Stability
`
`ADAMIS EXHIBIT 1016
`Page 194
`
`

`

`EPINEPHRINE
`
`195
`
`7. Analytical Methods
`7.1 Fluorometric
`7.2 Colorimetric
`7.3 Polarimetric
`7.4 Titrimetric
`7.5 Chromatographic
`7.51 Thin- layer and Paper
`7 . 52 Gas Chromatography
`7.53 Liquid Column Chromatography
`7 . 6 Spectrophotometric
`8. Acknowledgments
`9. References
`
`ADAMIS EXHIBIT 1016
`Page 195
`
`

`

`196
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`l. General Information
`
`1.1 Nomenclature
`
`1.11 Chemical Names
`l-a-3,4-dihydroxyphenyl-S-methylaminoethanol;
`l-l-(3,4-dihydroxyphenylJ-2-methylaminoethanol; 3,4-dihydroxy
`(l-hydroxy-2-methylaminoethyl)benzene; 1-methylaminoethanol(cid:173)
`catechol; 3,4-dihydroxy-a-(methylaminomethyl)benzyl alcohol;
`(R)-(-)-3,4-Dihydroxy-a{(methylamino)methyl]benzyl alcohol;
`4-[l-Hydroxy-2-(methylamino)ethyl]-l,2-benzendiol.
`1.12 Generic Name
`Epinephrine
`
`1.13 Trade Names
`Many trade names (1) exist for this drug.
`Some of the more conmlOnly used trade names in the United
`States are Adrenalin (Parke, Davis), Suprarenalin (Armour &
`Co.), and Suprarenin (Sterling Drug, Inc.).
`
`1.2 Formula
`
`1.21 Empirical
`c9a13N031 {OH) 2c6H3CHOHCH2NHCH3
`1.22 Structural and Stereochemical
`
`1.3 M:>lecular Weight
`
`1.31 Free Base
`183.21
`
`1.32 Bitartrate (l:l salt)
`333.30 (C9H13No3·c4H606)
`l.4 Elemental Composition (base)
`
`C 59%, H 7.1%, N 7.7%, 0 26.2%
`
`ADAMIS EXHIBIT 1016
`Page 196
`
`

`

`EPINEPHRINE
`
`197
`
`1.5 Description
`The USP XIX (2) describes epinephrine as "white to
`nearly white, odorless, microcrystalline powder or granules,
`gradually darkening on exposure to light and air. With acids,
`it forms salts that are readily soluble in water, and the
`base may be recovered by the addition of ammonia water or
`alkali carbonates. Its solutions are alkaline to litmus."
`
`1.6 Forms of Epinephrine Recognized in Official Compen(cid:173)
`dia.
`The USP XIX ( 3) contains e:pinephrine as the free base, the
`bitartrate salt, and the following formulations:
`
`Formulation
`
`Epinephrine
`Epinephrine Injection
`Epinephrine Nasal Solution
`Sterile Epinephrine Oil susp.
`Epinephrine Bitartrate
`Ophthalmic Solution
`Epinephrine Bitartrate for
`Ophthalmic Solution
`
`2. Physical Properties
`
`Category
`
`Bronchodilator
`Adrenergic
`Adrenergic
`Bronchodilator
`
`Adrenergic
`
`Adrenergic
`
`2.1 Associated with the Solid State
`
`2.11 Crystallinity
`Although epinephrine was the first hormone to
`be obtained in crystalline farm, crystallographic information
`with regard to crystalline structure is not available.
`Winchell ( 4) describes ~pinephrine as colorless or light
`brown crystals or powder which darkens on exposure to air
`and quotes refractive indices as determined by Keenan ( s ) as
`being N1 = 1.555, N2 = 1.733
`2.12 X-ray Diffraction
`Powder X-ray diffraction data (6) for epin(cid:173)
`ephrine are given in Table 1.
`
`2.13 Melting Point
`Kirk-Othmer ( 7) report the melting point of
`epinephrine as 211 - 212°c (215°C when heated rapidly) .
`
`ADAMIS EXHIBIT 1016
`Page 197
`
`

`

`10
`5
`10
`l~
`20
`10
`s
`10
`40
`5
`40
`
`1.41
`1.49
`1.55
`1. 70
`1. 77
`1.82
`1.87
`1.91
`1.95
`2.00
`2.05
`
`20
`10
`l~b
`3~
`30
`30
`10
`30
`10
`70
`20
`70
`5
`40
`40
`70
`so
`s
`10'1,
`70
`
`2.12
`2.18
`*2.29
`2.42
`2.51
`2.57
`2.69
`2.85
`2.99
`3.13
`3.27
`3.38
`3.60
`3.75
`3.91
`4.23
`4.58
`4.86
`5.13
`7.84
`
`I/Il hkl
`
`aj
`
`hkl
`
`I/11
`
`~
`
`Probably more than one line.
`,.
`
`MOL wt., 183.2
`Average temperature -17.4°c.
`College, Cardiff.
`Taken for the Institute of Physics at University
`
`Sign
`
`mp-'216d. Color White
`nwB
`
`t y
`
`c
`
`z
`A
`S.G.
`
`y
`Co
`
`D
`
`B
`bo
`
`Ref.
`2V
`F; a.
`
`Ref.
`a.
`~
`Sys.
`
`d corr. abs.? No
`Coll.
`Filter,Ni
`
`Cut off, 9.3
`:\ : 1,5418
`
`Ref., See below
`I/I1, Visual
`Dia. 19 cm
`Rad., Cul<a
`
`CH3-NH-CH2-CH OH
`
`Adrenaline
`
`70
`
`70
`
`70
`
`lOOb
`
`C9H1:JI03
`
`7.84
`
`4.23
`
`7.84
`
`5.13
`
`4-0232
`I/I
`
`4-0227
`
`d
`
`TABLE I. Powder X-ray Diffraction Data
`
`ADAMIS EXHIBIT 1016
`Page 198
`
`

`

`EPINEPHRINE
`
`199
`
`2.2 Solubility
`
`Solvent
`
`Temperature
`
`Solubility
`
`Reference
`
`Water
`Ethanol
`Ethyl Ether
`Chloroform
`
`20°c
`25°C
`
`l part in 3000
`l part in 2000
`insolubl e
`insoluble
`
`7
`1
`2
`2
`
`The solubility of ep inephrine in water is dependent on pH .
`It has minimal solubility at pH 9.4 and its solubility in(cid:173)
`creases as pH deviates from this value due to formation of
`water soluble species bearing net positive or negative
`charges.
`(See section on ionization in aqueous solution.)
`Aqueous alkaline systems are seldom employed because of sta(cid:173)
`bility considerations whereas at pH's of pharmaceutical or
`therapeutic importance the intrinsic solubility of epineph(cid:173)
`rine in water is adequate so as to not cause complications .
`
`2.3 Spectral
`
`2 . 31 Ultraviolet
`Epinephrine is reported (8,9) to have the fol(cid:173)
`lowing ul t r aviolet absorption characteristics in aqueous
`systems:
`
`Amax , n m
`
`(('.)
`
`--------------~----~-------.....>------------------------~
`('"'"anion (net charge-1 )
`cation lnet charge +1>"
`~-~------·"'-------.,
`~-~------~.-J<""-------~-~
`295(4400)
`243(7000)
`Sh285 ( 2500)
`280(2750) 224(6000)
`
`Isobestic points
`A, n m
`(cl
`
`281(2750)
`
`267 (1500)
`
`232(4900)
`
`2 . 32
`
`Infrared - The infrared spectrum of epineph(cid:173)
`arine is given in Fig . l .
`2 . 33 Mass
`The mass spectrum of epinephrine(iO) as ob(cid:173)
`tained on a mass spectrometer with an electron beam energy
`of 70 ev using the direct heated inl et system is shown in
`Figure 2. As discussed by the authors, phenylalkylamines
`such as epinephrine , noradrenalin, and isoprenaline which
`posess 2 phenolic hydroxyl groups give an observable
`
`ADAMIS EXHIBIT 1016
`Page 199
`
`

`

`PEPEaea NiAEEoe
`
`ceeeeeS
`
`pttnT[
`
`Pellet
`i a Figure1-InfraredSpectrumofEpinephrine,USP,Synthetic,KBr
`
`
`
`
`ieiNO
`it|oe :
`
`aos
`ne
`
`OH
`0
`
`ADAMIS EXHIBIT 1016
`Page 200
`
`ADAMIS EXHIBIT 1016
`Page 200
`
`

`

`e&o
`
`8
`
`:
`
`=
`
`~
`+I
`0
`
`~
`·rl
`ka
`~ ..c:
`0.
`0Fsoo
`GJ c:
`•rl
`o4
`0.
`GJ
`....
`°
`0
`f §
`g 3
`8. Cl)
`B
`nuw
`Ill
`Cl)
`i
`Z
`t
`
`-
`
`Ss
`
`=
`
`$
`
`ESS “
`N
`a
`GJ
`
`~ ·rl ra.
`
`|
`
`a
`
`........ ..... , ..
`
`°
`
`•
`
`sySiey eaqojey
`
`ADAMIS EXHIBIT 1016
`Page 201
`
`ADAMIS EXHIBIT 1016
`Page 201
`
`

`

`202
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`molecular ion. The 100% peak (m/e = 44) arises from 8 cleav(cid:173)
`For a thorough
`age with production of the CH2NHCH3+ ion.
`discussion on the topic of the mass spectra of phenylalkyl(cid:173)
`amine derivatives, the original article should be consulted.
`Further information pertinent to the identification of micro(cid:173)
`quanti ties of epinephrine can be obtained by mass spectros(cid:173)
`copy of the l-dimethylamino-5-naphthalenesulfonyl (Dansyl)
`derivative (11). Characteristics of the mass spectrum ob(cid:173)
`tained for the tridansyl derivative of epinephrine are shown
`in Table II.
`
`2.34 Optical Rotation and Dispersion
`The USP XIX (2) uses optical rotation as a
`criterion of acceptability and specifies it as follows:
`"The optical rotation of epinephrine as determined at 25°C on
`a2% solution in 0.5N HCl using sodium D light should not be
`less than -50° nor more than -53.5°."
`
`The optical rotatory dispersion curve of &pinephrine was de(cid:173)
`termined by Lyle (12) and also by Manna and Ghislandi (13)
`who extended rotatory dispersion studies to a series of epi(cid:173)
`nephrine derivatives. The dispersion ~pectrum is a plain
`curve over the region 700 to approximately 325 n m. Disper(cid:173)
`sion follows the Drude equation (14,15).
`
`with the constant A having a value of -32.3 (absolute etha(cid:173)
`nol, O.SN with respect to HCl as solvent and temperature of
`22°C). The dispersion curve obtained under these conditions
`is shown as Figure 3.
`
`These dispersion studies indicate that levorotatory epineph(cid:173)
`rine (that which is used medicinally and is contained in the
`USP XIX [2})has the D configuration.
`
`2.35 NMR
`The nuclear magnetic resonance spectrum of
`epinephrine is shown in Figure 4 (16). The peak assignments
`as per Jardetsky follow:
`
`Chemical shifts (in cps) of O.lM e:pinephrine in n2o with re(cid:173)
`spect to benzene as external standard
`
`ring
`-24.4
`
`CH
`94.2
`
`CH2
`195.1
`
`CH3
`224.5
`
`ADAMIS EXHIBIT 1016
`Page 202
`
`

`

`EPINEPHRINE
`
`203
`
`..... ········
`......
`. ...
`...
`. ····· ..
`..
`..
`..
`..
`...
`..
`. · .. ·
`.... ··
`
`.. . . . . : . .
`! . . . . . . .. -:
`
`-1
`
`-2
`
`-3
`
`-4
`
`.. I o(cid:173)
`... • -... --
`
`-7
`
`-8
`
`300 350 400 450 soa 550 600 650 700mjl
`Figure 3 - Optical rotary dispersion curve of epinephrine
`
`ADAMIS EXHIBIT 1016
`Page 203
`
`

`

`340
`
`371(2); 350(2).
`398(4); 384(2);
`605(3); 441.5(0.3};
`648(2); 630{0.5);
`868(0.5}; 864(0.5);
`
`30
`5
`---------
`M+ 234 250 263 277
`
`l
`
`40
`
`l
`
`882
`
`3
`
`C45H46N409S2
`
`of Inlet
`Temperature
`
`System
`
`oc
`
`(% Relative Abundance)
`
`Other Characteristic
`
`Peaks MW
`
`Relative Abundance
`
`of Peaks
`
`gt-
`MW
`
`Groups
`Danyl
`No. of
`
`Formula
`Empirical
`
`Instrument CHS, Varian Mat, electron beam energy 70 eV.
`The relative abundance of the peaks was established by comparison to m/e 170 (or 171) = 100%.
`Molecular weight and relative abundance of peaks for the dansyl derivative of Epinephrine.
`
`Table II
`
`ADAMIS EXHIBIT 1016
`Page 204
`
`

`

`pH 5. 6
`
`Figure 4 -NMR spectrum of O. 3M !-epinephrine in o2o. Temperature 27°
`
`3 ppm(&)
`
`4
`
`(Ji,
`
`s
`
`Qi
`
`HOO
`
`~
`
`! -Epinephrine 4.1M
`
`6
`
`7
`
`H B;
`
`CJtH n
`,ttff>
`I
`c-c-N-Oi~
`
`I
`
`I
`HO H H H
`
`I
`
`t«>-01
`
`ADAMIS EXHIBIT 1016
`Page 205
`
`

`

`206
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`The NMR spectrum of epinephrine and other biogenic phenyl(cid:173)
`alkamines was studied by Reisch et al (17) and found to be
`of value for their characterization.
`
`2.4 Distribution
`Epinephrine is not easily extracted from aqueous
`solution . Changes in pH do not significantly benefit ex(cid:173)
`traction s i nce epinephrine free base , like other catechol(cid:173)
`amines, is quite hydrophillic (18). Polar wa~er innniscible
`solvents (n-butanol, etc.) have been used to extrace epi(cid:173)
`nephrine from an aqueous phase .
`
`3.
`
`Ionization in Aqueous Solution
`
`Ionization characteristics of epinephrine and related
`compounds have been the subject of nllltlerous studies (19-26).
`Among these investigations that of .Martin ' s (24) is most de(cid:173)
`finitive since complications which arise from the presence
`of substituted annnonium and phenolic moieties having compar(cid:173)
`able acidities are considered.
`
`The first deprot6nation reaction of fully protonated
`epinephrine involves proton loss from both ammonium and
`phenolic groups and generates a mixture of zwitterionic and
`neutral molecules. This reaction is associated with a mac(cid:173)
`roscopic pKa of 8.69 (25°C, µ = 0.1) . The second deproto(cid:173)
`nation, associated with proton loss from the zwitterionic
`and neutral forms previously generated results in formation
`of a single specie bearing a net charge of -1 and is associ(cid:173)
`ated with a macroscopic PKa of 9.90 (conditions as before).
`The ionization sequence for epinephrine on a molecular level
`with corresponding microconstants follows:
`
`~1
`
`ADAMIS EXHIBIT 1016
`Page 206
`
`

`

`EPINEPHRINE
`
`207
`
`The ratio of tautomer ic molecules having no net charge, i.e . ,
`zwitterion/nonzwitterion, is approximately 4 at 25°C. This
`then means that the first deprotonation p r imarily involves
`proton loss from one of the phenolic hydroxyls, whereas the
`second is mainly loss from the amino group present in the
`zwitterion . The dist ribution of various species present in
`an aqueous solution of epinephrine as a function of pH is
`given in Figure 5. The ionization constants used in calcu(cid:173)
`lating this distribution were taken from Martin ' s work (24)
`as tabulated in Tabl e III. The isoelectric point of epin(cid:173)
`ephrine is 9.4.
`
`4. Biochemical Considerations
`
`Epinephrine is not active orally due to destruction in
`the gastrointestinal tract and conjugation and oxidation
`which occur in the liver (27). Normally the drug is admin(cid:173)
`istered parenterally , although preparations suitabl e for in(cid:173)
`halation are available to provide largely for a local effect
`in the lungs . Epinephrine is metabolized as in the following
`scheme (27) .
`
`HO-& ~ROH _ MA_ O**_
`RO~ ~·Of(
`0
`3,4-dehydroxymandelic
`acid
`
`l CCMI'
`H~ M-OH -
`
`HO~HOH
`HO~ 2H2
`MtCH3
`
`I CCMr*
`
`H3~~~~
`
`NHCH3
`
`metanepbrine l mjugm
`
`R3C~ CHOH
`
`MAO
`
`3-met hoxy -4 -hydroxy
`mande lie acid
`
`3·methoxy-4• hydroxy(cid:173)
`phenylglycol
`
`H3C~yHOH
`H~ 9H2
`NHCR3
`metanephrine
`sulfate or glucuronide
`
`* Catechol- 0-methyltransferase
`**Konoamine oxidase
`
`ADAMIS EXHIBIT 1016
`Page 207
`
`

`

`208
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`l.00
`
`0.80
`
`0 . 60
`
`c:
`0 ....
`41
`~ 0 40
`...
`r:r..
`
`0.20
`
`+l charge
`
`-1 charge
`
`/
`
`no net chnge
`
`0.00
`
`4
`
`5
`
`6
`
`7
`
`10 11
`
`12
`
`13
`
`14
`
`Pk1
`
`pk2
`
`pH
`
`Figure 5 - Species distribution diagram for epinephrine
`
`ADAMIS EXHIBIT 1016
`Page 208
`
`

`

`0.10
`0.10
`
`-o
`
`µ
`
`20
`25
`
`25
`
`0.41
`0.32
`
`0.50
`
`3.8
`7.1
`
`4.3
`
`9.39
`9.57
`
`8.81
`8.72
`
`9.90
`9.95
`
`8.71
`8.66
`
`9.51
`
`8.88
`
`10.10
`
`8.79
`
`Epinephrine
`
`T °C
`
`pk21 -Pk1
`
`R = k1/k2
`
`pk2
`
`pk1
`
`pK2
`
`PKl
`
`Table III
`
`ADAMIS EXHIBIT 1016
`Page 209
`
`

`

`210
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`5. Synthesis
`
`A crystalline compound was first isolated from suprarenal
`medulla extracts by Takamine (28) and Aldrich (29) which
`showed the same pharmacological action as extracts from this
`gland. This compound was later characterized as l-a- 3,4-
`dihydroxyphenyl- 8-methyl- aminoethanol primarily through the
`work of Pauly (30)and Jowett (31). Resolution of racemic
`epinephrine as first synthesized by Stolz and Dakin (32,33)
`was effected by Flacher (34) and it was found that the syn(cid:173)
`thetic 1- isomer wa.s identical with that isolated from the
`natural source .
`
`Many catechol sympathomimetic amities are synthesized on
`a commercial scale by essentially the same process. This
`process (35) can be divided into 4 stages, i.e.,
`
`l. production of chloracetocatechol,
`2. conversion of chloracetocatechol to adrenalone
`hydrchloride by reaction with methylamine ,
`3. purification of the adrenalone as produced in 2
`and reduction of the salt to racemic epinephrine,
`resolution of the resulting racemate to yield the
`desired
`levo isomer which is generally accomplished
`by crystallization from methanol as the tartrate .
`
`4.
`
`A flow diagram for this process ( 35) follows:
`
`ClCH2COOH
`
`CCl4
`
`POCl3
`
`0
`
`H09~-CH2Cl
`HO
`
`+
`
`uo}O)
`
`HO
`
`catechol
`
`{}OH
`HO
`i -CHzNHCH3
`
`HO
`
`racemic epinephrine
`
`Hz
`
`Pd/C
`catalyst
`
`chloroacetocatechol
`
`I CH3NH2
`
`HO~ g -CH2NHCH3
`
`HO
`
`adrenalone
`
`ADAMIS EXHIBIT 1016
`Page 210
`
`

`

`EPINEPHRINE
`
`211
`
`6. Stability and Behavioral Chemistry
`
`6.1 Solid State
`Epinephrine is a relatively unstable compound and
`is susceptible to decomposition in the solid state . Special
`precautions must be observed during the synthesis of the
`free base, and material so obtained should be stored under
`regulated conditions, i.e . , N2 atmosphere, amber bottles,
`etc. (35).
`In regard to the stability of the solid base,
`moisture content appears to be a significant factor since
`thoroughly dried material is more stable than that which
`has a significant moisture content .
`
`6 . 2 Aqueous Solutions
`6 . 21 Racemization
`Epinephrine racemizes at an appreciable rate
`even at near ambient temperature. Data obtained by Kisbye
`and Schroeter (36,37,38) indicate that racemization of epi(cid:173)
`nephrine is acid catalyzed . This is an important considera(cid:173)
`tion in dosage form design since an acidic environment is de(cid:173)
`sirable in regard to prevention of discoloration. Estimates
`of the rate of racemization at near ambient temperatures are
`given in Table IV (38) .
`
`At pH 3 . 5 or less , racemization occurs by an SN type re(cid:173)
`action. This acid catalyzed reaction is thought to occur by
`rapid protonation of the secondary alcoholic oxygen atom fol(cid:173)
`lowed by rate determining elimination of this hydroxyl as
`water. Attack of a second molecul e of water on the shielded
`incipient carbonium ion then results in production of the
`optical isomer. Since the same reaction occurs on the .9_-iso(cid:173)
`mer, a racemic mixture results. The Q-isomer of epinephrine
`has little pharmacological activity as compared to the 1-
`isomer.
`
`6.22 Reaction with Bisulfite
`Cl osely allied with epinephrine's racemization
`reaction is its reaction with anions of sulfurous acid. Bi(cid:173)
`sulfite or metabisulfite salts are frequently used as anti(cid:173)
`oxidants in aqueous formulations of epinephrine where they
`function to retard color formation.
`
`Initial studies (39 1 40) demonstrated that the potency of sol(cid:173)
`utions of epinephrine could be lost without discoloration or
`true racemization being the cause. Further, it was shown
`that at pH
`4 . 7 or higher, epinephrine was lost more rapid(cid:173)
`ly in the presence of bisulfite than in its absence.
`
`ADAMIS EXHIBIT 1016
`Page 211
`
`

`

`6 min. (ca. 36 mo.)
`6 min. (ca. 120 mo.)
`5 min. (ca. 10 mo.)
`6 min.
`(ca. 35 mo.)
`1.1 X 10 min. (ca. 2 mo.)
`5
`4.0 X 10 min. (ca. 9 mo.)
`
`1.6 X 10
`
`5.5 x 10
`
`4.3 x 10
`
`l. 5 X 10
`
`5
`
`(ca. 17 mo.)
`5
`6 min. (ca. 60 mo.)
`5 min. (ca. 5 mo.)
`(ca. 17 mo.)
`5
`
`7.5 X 10 min.
`2.6 X 10
`
`2.0 X 10
`
`7.3 X 10 min.
`5.4 X 10 min. (ca. l JJW:).)
`l. 9 x 10 min. (ca. 4i, mo.)
`
`4
`
`5
`
`Act:ivityb
`90' Optical
`
`Time of Minimum
`
`Activity
`a
`9 S' Opt.i cal
`
`.
`
`.
`
`Time of Minimum
`
`6.77 x 10-s
`1.91 x lo-8
`2.45 x 10-7
`6.92 x 10-8
`9.34 x 10-7
`2.63 x 10-7
`
`pB 3. 5, 35°
`pH 3.5, 2s0
`pH 3.0, 35
`0
`pH 3.0, 25°
`pH 2. 5, 35 0
`pH 2.5, 25°
`
`Predicted Rat:~1
`
`Constant:, Mi.n.
`
`TABLE IV -Predicted Rates and Times of Maintenance of a Minimum 95 and 90 Per Cent Optical
`
`Activity
`
`ADAMIS EXHIBIT 1016
`Page 212
`
`

`

`EPINEPHRJNE
`
`213
`
`Subsequent investigation (41) demonstrated that anions of
`sulfurous acid actually react with epinephrine to produce 1-
`(3,4-dihydroxyphenyl)-2-methylaminoethane sulfonic acid
`according to the following equation:
`9
`e
`a
`103
`+ so3 = R~CH~CH2NH2CH3 + OH9
`3
`
`NH2CH
`2
`
`R-CHOHCH
`
`R = HO:?
`
`The kinetic behavior of epinephrine's reaction with bisul(cid:173)
`fite is explicable on the basis of the following reaction
`scheme ( 41) •
`
`,,
`k,
`l-Ep - - Ep• - - d 1-Ep
`lit·
`... 1
`so.-i
`so.-
`
`EpBi (racemic product)
`
`Rate measurements were consistent with and indicative of the
`following expression which describes the rate of loss of
`epinephrine from bisulfite containing aqueous solution. (41)
`
`-d(Ep) = k1(so.-) k,(Ep) + k (E )(SO•)
`k, + k,(SO,-)
`' P
`di
`•
`
`The preceding studies showed that since sulfite is so much
`more reactive than water, epinephrine does not racemize when
`bisulfite is present.
`In the presence of bisulfite, optical
`and physiological activity is lost through formation of the
`sulfonate.
`
`6.23 Oxidation
`Since epinephrine is an o-diphenol contain(cid:173)
`ing a hydroxyl group in the a position, it is a strong re(cid:173)
`ducing agent (42). As such, it is easily oxidized by such
`oxidizing agents as molecular oxygen, iodine, potassium fer(cid:173)
`ricyanide, potassium persulfate, and manganese dioxide. Oxi(cid:173)
`dation of epinephrine is thought to occur through the trans(cid:173)
`ient formation of epinephrine quinone with formation, under
`proper conditions, of adrenochrone (43,44,45,46). Oxidation
`of epinephrine by molecular oxygen can also result in forma(cid:173)
`tion of a brownish insoluble material of indefinite struc(cid:173)
`ture. An investigation of the oxidation of epinephrine by
`molecular oxygen (47) indicated that the reaction involved
`is extremely complex. Data obtained suggests that oxidation
`
`ADAMIS EXHIBIT 1016
`Page 213
`
`

`

`214
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`of epinephrine in aqueous solution can occur in the absence
`of heavy metal ions and likely involves free radical se(cid:173)
`quences. Oxidative discoloration of epinephrine solutions
`occurs more rapidly as pH is increased.
`
`6.24 Miscellaneous Reactions
`In addition to the preceding reactions which
`are relevant to dosage form design, manufacture, and storage,
`epinephrine can undergo a variety of other reactions which
`have relevance to other areas. Reaction products of these
`reactions and conditions are summarized in table 5 .
`
`6.25 Dosage Form Stability
`Available information indicates that oxida(cid:173)
`tion of epinephrine in aqueous dosage forms is an extremely
`important consideration in regard to dosage form design, man(cid:173)
`ufacture, and storage. This is the situation because oxida(cid:173)
`tion produces both inactivation and discoloration . Dis(cid:173)
`colored solutions of epinephrine are considered to be un(cid:173)
`usable ( 2) regardless of potency.
`
`Published reports (51,52,53) indicate that the kind of con(cid:173)
`tainer (ampoule vs. multiple dose vial) significantly influ(cid:173)
`enced shelf life. Epinephrine solutions formulated with
`rnetabisulfite contained in ampoules did not show significant
`formation of 1-(3, 4-dihydroxyphenyl)-2-methylaminoethane sul(cid:173)
`fonic acid even after 7 years storage at 15°c. Racernization
`of the epinephrine contained in these ampoules was likewise
`insignificant. Results of stability studies of epinephrine
`ampoules using various analytical probes are given in Table
`VI
`(52).
`
`7. Analytical Methods
`
`7.1 Fluorometric
`Measurement of native or induced fluorescence pro(cid:173)
`vides a useful means of assaying epinephrine. While the
`scope of this analytical approach is limited, in that stereo(cid:173)
`selectivity is not attainable, sensitivity and a fair degree
`of analytical specificity are provided .
`
`Naturally occurring catecholamines such as epinephrine, nor(cid:173)
`epinephrine, dopa, and dopamine possess native fluorescence
`(54 1 55). All of these compounds are maximally excited at
`285 nm and fluoresce at 325 nm. Since several catechol(cid:173)
`amines which occur in living tissue possess essentially the
`same fluorescent characteristics, native fluorescence is not
`
`ADAMIS EXHIBIT 1016
`Page 214
`
`

`

`EPINEPHRINE
`
`215
`
`Tabla V
`
`Prod11eu Po,_d t~ tpinephdne
`
`lteaction Product
`
`... cuon ConditioM
`
`bferanc•
`
`IC1ld condit1on1 of pH and Ullperatw:a.
`·or 803 •
`Pr . . ance of KSo
`3
`
`1• (l, 4•d1hydroicyphenyl)-
`2•Mthylaoa.lnoethana •111-
`fOftic ac:ld
`
`1109-Cll:zCHO; N112CH3
`
`IUong acid and h19h t.-peratw:•.
`
`48
`
`llO
`l, 4-<llhydroll)'pMnyl
`thyl
`acetaldahy<k1 •
`- i ...
`
`A.d&'enochrom
`
`Adrenolutine
`
`lli ld cond1tlono, oddation (1
`
`, o
`
`2
`
`2
`
`ate)
`
`0-46
`
`Mlld ~ratu.re oondltions, oJdcl&tion
`in baolc envlro.,..nt
`
`0 · 46
`
`Variable pH, reaction occw:a more
`rapldly at lov pH, relatively &ild
`oondltlon•
`
`36, 37, 39
`
`Oi&4rena line ether
`
`&lavated t .uiperatu.r·e , 1tron9 acid
`
`50
`
`3, 4-dihydro•yacetophanona,
`Mttlyl ulna
`
`eo.iplex Ion• containln9
`epinephrine and boron
`
`JCUd condi t1on1. Preoence of
`anion• of boric acid
`
`106,107
`
`ADAMIS EXHIBIT 1016
`Page 215
`
`

`

`216
`
`DALE H. SZULCZEWSKJ AND WEN-HAI HONG
`
`1h• Stabil.tty ol Adcenal1n• rnject1on.sa
`(pH adjust~ to J·O l>y addJ.tion of hijdrochlorJc •c1dl
`
`'rABU VI
`
`HBIJt
`tr•atment
`
`lh\heated
`
`100°
`20 lllin.
`
`120°
`20 .Un.
`
`Ad.ren.line recovery .in pt1r c•nt of orJ.g1n•l content
`
`Stor•ge
`per.tod
`(=nth•)
`
`pH
`
`Color
`
`Colori.Mtrlc
`Nthod
`
`PJuori•tric
`method
`
`R•t b. p. Rat ut•rua
`..,thod
`•thod
`
`0
`6
`20
`
`0
`6
`20
`
`0
`6
`20
`
`3.0
`3.0
`3.0
`
`color le.as
`light red
`light red
`
`l.O
`3.0
`3.0
`
`colorleaa
`ll9ht br"""
`light br°""
`
`100
`99
`99
`
`101
`99
`98
`
`3.0
`3.0
`3.0
`
`light red
`99
`brown t dArk: ppt. 99
`brown, da~ ppt. 96
`
`102
`100
`
`106
`96
`97
`
`100
`95
`95
`
`98 (96-l04)C 102 (86-116)
`94 (95-106)
`90 (92-109)
`
`99 (98-103)
`99 (97-103)
`97 (94-106)
`
`99 (87-115)
`98 (89-112)
`104 (92-109)
`
`92 (95-105)
`93 (97-104)
`92 (91-110)
`
`94 (94-106)
`88 (90-lll)
`83 (88-113)
`
`The St<lbility ot Adrenaline J:njectlons1'
`(pH adjusted to 3.6 b!I addJ.ng sodiU1lt metab1sulphiteJ
`
`treot . . nt
`
`p&riod
`(.onthaJ
`
`Unheated
`
`100°
`20 .Un.
`
`120
`20 min.
`
`0
`6
`20
`
`0
`6
`
`0
`6
`20
`
`""
`
`3.6
`3.4
`3.4
`
`3.4
`3.3
`
`J.4
`3. 3
`3.3
`
`AdZBMHM r'1COVOZ!/ .tn pet' C4tnt of or.S.ginal contBnt
`
`Color
`
`Colorimetric Tluor1metr1c
`. . tho4
`-tho4
`
`/141t b. p. R•t uterus
`.et:hod
`
`_.,,.,.,
`
`colorless
`
`colorless
`
`colorlees
`
`99
`100
`100
`
`99
`100
`
`98
`99
`99
`
`102
`97
`100
`
`101
`96
`
`94
`95
`98
`
`100 (95-l05)C 101 (92-109)
`87 (89-113)
`100 (93-108)
`
`96 (94-106)
`100 (97-103)
`
`97 (93-108)
`96 (93-108)
`
`97 (93-108)
`98 (94-106)
`97 (95-106)
`
`100 (84-120)
`98 (89-113)
`94 (83-121)
`
`•Actrena1Jne b1t.trtra.te 1 .82 gm, sodium chloride B.O gm, hl}drochJ.or1c •c1d q.•., pH J.0, Water
`tor injection lOOO ml.
`
`bits aboV8 eXC"ept Mdrochlor1c acid OOtttte<I and O.S 'Jf" a<>d.lwt •tabi•ulflte •d<led. PH J.6.
`
`cFJ.ducl•l llmits, In parentM~i.s, 11re e xpro••ed a• percent•~• (I' • 0.05).
`
`ADAMIS EXHIBIT 1016
`Page 216
`
`

`

`EPINEPHRlNE
`
`217
`
`commonly employed in the assay of a particular hormone or
`compound in body fluids or tissue . Application of this phe(cid:173)
`nomenon, however, has been made to dosage form analysis (56) .
`
`Primarily because epinephrine's native fluorescence occurs
`in the ultraviolet range, need existed for an analytical
`approach which would produce fluorescence in the visible re(cid:173)
`gion. Two general schemes evolved to provide this. The
`first of these involves production of a highly fluorescing
`hydroxyindole by oxidative cyclization of epinephrine under
`basic conditions. The second involves production of a flu(cid:173)
`orescent quinoxaline.
`
`As was observed by Loew (57), epinephrine produces a highl y
`fluorescent material when oxidized in a basic aqueous envi(cid:173)
`ronment .
`Initial investigations (58-61) indicated that assay
`of epinephrine on this basis was feasible. The nature of the
`reaction involved in producing the fluorescing material was
`studied, and it was determined that the fluorescing material
`produced is a hydroxyindole formed as in the following scheme
`(43- 46).
`
`B)J.:~H
`HO ~
`CH.
`
`-2H
`
`Epinephrine
`
`H~.
`OH
`OH-
`7
`n~ anaerobic
`I
`BO
`CH1
`
`Ep\nepbrlne-quinone
`{-2H
`
`A.drenol11t1ne
`(3, 5, e- trlhydroxy-1-methyllndole)
`
`Adrenochrome
`
`The chemistry of adrenochrome has been reviewed (62). The
`fluorometric analysis of epinephrine, based on production of
`the trihydroxyindole derivative, has undergone extensive mod(cid:173)
`ification and is still being modified (63) to provide for a
`ll¥'.>re reliable or selective procedure. The method has been
`used extensively for analysis of catecholamines in body
`
`ADAMIS EXHIBIT 1016
`Page 217
`
`

`

`218
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`fluids (54) as well as for analysis of epinephrine in dosage
`forms (63) . For a thorough review of this procedure in re(cid:173)
`gard to analysis of epinephrine in body fluids or tissues,
`a basic text should be consulted (54) .
`
`The second approach used in fluorimetric assay of epinephrine
`and other catechol amines involves condensation with ethylene(cid:173)
`diami ne. While this has been applied quite extensively to
`analysis of epinephrine and norepinephrine in biological
`systems, no examples of applications to dosage form analysis
`have appeared.
`Investigations reported thus far (64-69) sug(cid:173)
`gest that epinephrine reacts with ethylenediamine in the fol(cid:173)
`lowing manner .
`
`+
`
`ED
`
`Adrenaline
`
`Adrenochrome
`
`~N0-iCHOH_-H._ (ITj--(°H
`N~~)c• H,
`~~/
`bI
`CH1
`
`A different product is produced from norepinephrine's reac(cid:173)
`tion , i.e.,
`
`CHOH
`HO
`~yH.
`+ ED
`HO,JV
`NH,
`
`Noradrenaline
`
`ADAMIS EXHIBIT 1016
`Page 218
`
`

`

`EPINEPHRINE
`
`219
`
`The quinoxaline produced from norepinephrine has different
`fluorescent characteristics than the hydroxyindole produced
`by epinephrine permitting simultaneous determination of both
`compounds in biological samples. Details of this procedure
`can be found in a basic text (70).
`
`7.2 Colorimetric
`Colorimetric procedures which have been applied to
`analysis of epinephrine are based on the presence of the cate(cid:173)
`chol or phenolic groups and hence have a variable degree of
`selectivity . Some of the more recently developed colorimet(cid:173)
`ric procedures are reasonably selective; however, since none
`are stereoselective, their application is limited to those
`situations where enantiomorphic composition is determined in(cid:173)
`dependently or the much less potent d-isomer is known to be
`absent. Other common sources of analytical interference in(cid:173)
`clude biogenic catecholamines (norepinephrine) and the sul(cid:173)
`fonated product which results from reaction of bisulfite and
`epinephrine.
`
`Barker et al (71) in a critical survey of colorimetric pro(cid:173)
`cedures for epinephrine indicated that a colored material
`could be produced from this hormone by oxidation with potas(cid:173)
`sium persulfate . The procedure was confirmed by Rees (72)
`and shown to give results which were in accord with those ob(cid:173)
`tained pharmacologically. Details of this procedure are given
`in Garratt's text on the quantitative analysis of drugs (73).
`Other oxidizing agents such as iodine (74) have been used to
`generate a colored product and provide differentiation between
`epinephrine and norepinephrine in biological samples. One
`complication which arises in analytical colorimetric schemes
`involving oxidation is that bisulfite is known to interfere.
`Doty's (75) method which employs ferrous ion to generate
`color copes with this problem in the sense that interference
`from anions arising from sulfurous acid is no longer apparent:
`however, epinephrine sulfonate may interfere. A more recent
`approach to colorimetric determination of epinephrine (76)
`involves reaction of thiosemicarbazide with epinephrine under
`basic conditions. Under the conditions of this procedure,
`apparently only catechols yield a colored product.
`
`Other color producing reactions which involve epinephrine are
`known. Some of these are useful for identification of the
`hormone (50), while others serve as means of detection in
`paper and thin layer chromatography. (42,83)
`
`ADAMIS EXHIBIT 1016
`Page 219
`
`

`

`220
`
`DALE H. SZULCZEWSKI AND WEN-HAI HONG
`
`7.3 P.olarimetric
`Methods which involve measurement of opti cal rotation
`have been proposed and are used to assay epinephrine in dos(cid:173)
`age forms . Several factors restrict the direct application
`of polarimetric methods and require that they be used in con(cid:173)
`junction with other procedures. A primary consideration in
`this regard is that loss of optical acticity can be associated
`with either complete or only partial loss of pharmacological
`activity. Unless an ancillary method is used which assays
`total {d + 1) epinephrine content, correlation of observed ro(cid:173)
`tation and 1 - epinephrine content is not possible.
`
`This problem was recognized by Rosenblum, Goldman, and Feld(cid:173)
`man (77) as well as Hellberg (78) who used concurrent polari(cid:173)
`metric and colorimetric measurements to determine epinephrine
`content. Unfortunately the colorimetric procedures used are
`not selective and interference from other chromogenic com(cid:173)
`pounds associated with epinephrine is possible . Nevertheless
`their approach is valid and if a more selective procedure
`{e.g., Prasad ' s fluorometric method [63)) is used to estimate
`total (d + 1) epinephrine, accurate results may be expected .
`
`An