Development of sarpogrelate external preparation for intractable pain control. I. Pre-formulation study on application of modified β-cyclodextrins

Article abstract of DOI:10.1248/cpb.58.45

To optimize the formulation of in-hospital sarpogrelate (SPG) preparation for external use, various cyclodextrins (CDs) were investigated for their ability to improve the aqueous solubility and chemical stability of SPG. Although hydrolysis of SPG was mar

Full text of DOI:10.1248/cpb.58.45

January 2010
Chem. Pharm. Bull. 58(1) 45—50 (2010)
45
Development of Sarpogrelate External Preparation for Intractable Pain
Control. I. Pre-formulation Study on Application of Modified
b-Cyclodextrins
a,b
a
a
b
a
Kazumi HANAWA, Takehisa HANAWA, Chikako TSUCHIYA, Kenjirou HIGASHI, Masahiko SUZUKI,
b
b
,a
Kunikazu MORIBE, Keiji YAMAMOTO, and Toshio OGUCHI*
a
Department of Pharmacy, University Hospital, University of Yamanashi; 1110 Shimokato, Chuo, Yamanashi 409–3898,
b
Japan: and Graduate School of Pharmaceutical Sciences, Chiba University; 1–33 Yayoi-cho, Inage-ku, Chiba 263–8522,
Japan. Received July 31, 2009; accepted October 9, 2009; published online October 14, 2009
To optimize the formulation of in-hospital sarpogrelate (SPG) preparation for external use, various cy-
clodextrins (CDs) were investigated for their ability to improve the aqueous solubility and chemical stability of
SPG. Although hydrolysis of SPG was markedly accelerated at above pH 7.0 in aqueous solution, the addition of
®
modified b-CD resulted in suppressed SPG hydrolysis. Addition of sulfobutylether-b-CD (SBE-b-CD, Captisol )
1
had the most significant stabilization effect. Phase solubility diagram and H-NMR analyses indicated that di-
methyl-b-CD and SBE-b-CD formed significantly stable inclusion complexes with SPG in aqueous solution,
thereby contributing to both the increased solubility and chemical stabilization of SPG. In terms of the clinical
safety of CD derivatives, SBE-b-CD was determined to be the most suitable solubilizing agent for external SPG
preparation.
Key words sarpogrelate; cyclodextrin; stability; solubility; in-hospital preparation; pain control
The importance of pain control is increasing due to the in- obtained by the ring-opening polymerization of ethyleneox-
creasing number of patients suffering from intractable ide, giving it high viscosity and spinnability. Ointments pre-
chronic pain as the population ages. In a number of cases, pared with these water-soluble polymers showed the im-
pain cannot be well controlled due to obscure etiology of provement of the spreading properties compared with the
chronic pain or hyperalgesia. As postherpetic or neuropathic ointment containing white petrolatum as the ointment base.
pain is difficult to cure completely, nerve block and physical Thus, we prepared the aqueous gel as an external formulation
therapy as supportive measures are often implemented. Non- for administration of SPG to treat peripheral neuralgia. How-
steroidal anti-inflammatory drugs (NSAIDs), tricyclic anti- ever, SPG is slightly water soluble (0.012 g/ml) and it can
depressants, Chinese herbs, systemic corticosteroids or topi- easily be hydrolyzed at the ester moiety in its chemical struc-
12)
cal steroids for use in medical treatment are also known to be ture. Therefore, an improvement in the solubility is re-
effective.
Sarpogrelate [{8R,S}-1-[2-[2-(3-methoxyphenyl)ethyl]phe-
quired to prepare aqueous gels of SPG.
To improve the solubility and stability of SPG in the
noxy]-3-(dimethylamino)-2-propyl hydrogen succinate hy- formulation, we have therefore been examining the use of
drochloride] (SPG) is a selective 5-HT2A receptor antagonist additives, such as cyclodextrins (CDs). CDs can form inclu-
that was introduced as a therapeutic agent for thrombosis- sion compounds which are used for various research applica-
1
3—16)
associated ischemia. With its high affinity for 5-HT2A recep- tions.
Applicability of CDs were investigated in order to
tor, SPG is reported to have significant analgesic effect in enhance the solubility and stability of SPG in the external
1—3)
rats when intrathecally and systemically administered.
Topical ketanserin, another selective 5-HT2A antagonist, also
attenuated hyperalgesia and inflammation in arthritic rats.
Based on these animal studies, development of a rapidly act-
preparations.
4)
Experimental
Materials SPG was generously supplied from Mitsubishi Tanabe
Pharma, Co., Ltd. (Tokyo, Japan). a-CD and b-CD (Wako Pure Chem. Ind.,
ing treatment for patients suffering from chronic pain due to Ltd., Osaka, Japan), g-CD (Kanto Chem. Co., Tokyo, Japan), hydroxy-
peripheral neuralgia has been the major research focus.
Recently, a transdermal ointment in which the crushed
SPG tablet [containing 5% (w/w) SPG as the active ingredi-
ent; and other excipients: D-mannitol, potato starch, and par-
tially saponified polyvinyl alcohol] is dispersed in white
propyl-b-cyclodextrin (HP-b-CD; Nihon Shokuhin Kako Co., Tokyo,
Japan), 2,6-di-O-methyl-b-cyclodextrin (DM-b-CD; Toshin Chemical Co.,
®
Tokyo, Japan). Sulfobutyl ether-b-cyclodextrin (SBE-b-CD, Captisol , DS
6.55) were kindly received from CyDex pharmaceuticals, Inc. Lenexa, KS,
U.S.A.
Determination of SPG Concentration SPG concentration in the sam-
petrolatum has been shown to be effective against post- ple solution was determined by the internal standard method in HPLC analy-
5
)
sis. HPLC apparatus consisted of a detector (SPD-10AVP), column oven
CTO-10AVP), and calculator (C-R8A272 nm; Shimadzu Co., Kyoto,
Japan). Measurement conditions were as follows: column, Shodex C18M-
D (4.6 mm i.d.ꢀ150 mm; Showa Denko Co., Ltd., Tokyo, Japan); column
temperature, 30 °C; mobile phase, methanol : 0.05 M KH PO (70 : 30); flow
herpetic pain. However, due to its surface stickiness from
white petrolatum and rough surface from the crushed SPG
tablet, a reduction in compliance with drug treatment in some
(
4
5—7)
patients is a concern.
2
4
In our previous studies, we prepared an aqueous gel of rate, 0.8 ml/min; internal standard, propyl p-hydroxybenzoate (0.1→250 in
acetonitrile).
water-soluble polymers iota-carrageenan and polyethylene(oxide)
as an external formulation with improved compliance.
Iota-carrageenan has been used as a texture modifier and a
Stability of SPG in Aqueous Solutions at Various pH A definite vol-
8—11)
ume of SPG aqueous solution (1.0 ml; 100 mg SPG/1 ml H O) was added to
2
9.0 ml of 0.10 M phosphate buffer solution (pH 4.0, 6.0, 7.0, 8.0, 9.0) and in-
gelling agent in the food industry, and polyethylene(oxide) is cubated at 50 °C. A 250-ml aliquot of the mixture was removed at designated
∗
To whom correspondence should be addressed. e-mail: toshioo@yamanashi.ac.jp
© 2010 Pharmaceutical Society of Japan

4
6
Vol. 58, No. 1
Fig. 1. Scheme of Sarpogrelate (SPG) Hydrolysis
time intervals, and the amount of remaining SPG was determined with
HPLC. All experiments were performed in triplicate.
Solubility Study Excess amount of SPG (300 mg : 0.6 mmol) and suc-
cessively increasing amounts of each CD were combined in 10 ml of 0.10 M
HCl. The samples were shaken at 25 °C for 24 h. After equilibration, the
samples were filtered with a Millipore filter (0.2 mm). The amount of SPG
dissolved was analyzed by HPLC.
Stability of SPG in Aqueous Solutions by Adding Various CDs The
mixture of SPG and CDs at different molar ratios (1 : 5.0, 1 : 50 or 1 : 500)
was dissolved in 0.10 M phosphate buffer solution (pH 7.0) and incubated at
2
5, 37 or 50 °C. A 250-ml aliquot of the mixture was removed at designated
time intervals, and the amount of remaining SPG was determined with
HPLC. The activation energy (E ) of SPG hydrolysis was calculated accord-
a
ing to the Arrhenius equation.
1
H-NMR and 2D-ROESY Spectroscopy The formation of a complex
1
Fig. 2a. SPG Hydrolysis of in Aqueous Solutions at Various pH and 50 °C
between SPG and CDs was investigated by NMR spectroscopy. H-NMR ex-
periments were performed at 25 °C in D O on a Varian Inova 500 spectrome-
ꢀ, pH 4.0; ꢁ, pH 6.0; ꢂ, pH 7.0; ꢀ, pH 8.0; ꢃ, pH 9.0. Each point represents the
meanꢅS.D. (nꢄ3).
2
1
ter (Palo Alto, CA, U.S.A.) operating at 500 MHz. H-NMR spectra were ac-
1
quired with 64 scans with a H excitation pulse of 7.4 ms; the time between
each repetition was set to 10 s to allow for full relaxation of proton magneti-
1
zation. The H-NMR spectra were acquired with a spectral width of
8
000.0 Hz (ꢀ16.0 ppm) and 64 K data points, providing a digital resolution
of 0.1 Hz. The spectra were acquired with the same spectral conditions as
1
1
H-NMR. The H spectra were processed by applying a Fourier transform
with zero-filling to 64 K data points and by an exponential multiplication of
1
the FIDs by a factor of 0.3 and 1 Hz for H-NMR, respectively. Attributions
of SPG and CDs were realized by chemical shifts observed on the NMR
spectra for each mixture at various molar ratios of SPG and CDs. When the
stoichiometry was assumed to be 1 : 1, the dissociation constant between
17)
SPG and CDs were given by Eq. 1
:
(
δobsꢁδ ) / (δELꢁδL )
L
2
ꢄ((E ꢂL ꢂK )ꢁ (E ꢂL ꢂK ) ꢁ 4E L ) / 2LT
(1)
T
T
d
T
T
d
T T
where K is dissociation constant, E is total CD concentration, LT is total
d
T
SPG concentration, dobs is observed chemical shift of the SPG proton, dL is
chemical shift of the proton in pure SPG and dEL is chemical shift of the
proton in pure complex. The 2D-NMR experiments were acquired using the
ROESY (rotating-frame Overhauser effect spectroscopy) pulse sequence on
a Bruker Avance500 spectrometer (11.7 T) (Karlsruhe, Germany). The spin
Fig. 2b. Apparent First-Order Rate Constant (k) of SPG Hydrolysis in
Aqueous Solutions as a Function of pH at 50 °C
hydrolysis reaction appeared to proceed not only in the
ꢁ
lock time, relaxation delay and temperature was set to 300 ms, 1 s and 20 °C, de-protonated form (–N(CH ) and –COO ) but also in the
3
2
ꢂ
ꢁ
respectively. A spectral width was 3472 Hz (6.94 ppm) for SBE-b-CD–SPG
system and 2765 Hz (5.53 ppm) for DM-b-CD–SPG system, respectively.
The obtained 160ꢀ2048 K data matrix in f2 and f1 was zero filled prior to
Fourier transformation, resulting in a 2048ꢀ2048 spectral data matrix.
zwitterionic form (–N (CH ) H and –COO ) of SPG.
3
2
Phase Solubility Diagrams of SPG with Various CDs
Interaction between SPG and various CDs in 0.10 M HCl was
Chemical shifts were given in ppm in relation to the water residue signal at studied using their phase solubility diagrams (Fig. 3). In all
4
.824 ppm.
the systems, apparent solubility of SPG increased linearly
with an increase in the amount of CD added, demonstrating
18)
Results and Discussion
an A type phase solubility diagram. By assuming 1 : 1 sto-
L
Hydrolysis of SPG in Aqueous Solutions at Various pH ichiometry in the solution, stability constants of the com-
Kinetics of SPG hydrolysis (Fig. 1) was investigated in the plexes were calculated according to Eq. 2 (Table 1). Among
aqueous buffer solution of various pH at 50 °C, and the semi- unmodified CDs (a-, b-, and g-CD), the complex with b-CD
ꢁ1
logarithmic plots of % SPG remaining are shown in Fig. 2a. was the most stable with a stability constant of 877 M
SPG hydrolysis occurred according to first-order kinetics at
all values of pH, and the apparent rate constants (k) obtained
.
ꢁ1
stability constant (M ): Kꢃꢄslope/interceptꢀ(1ꢁslope)
(2)
from the slope of the plots were plotted against pH (Fig. 2b).
In the complexes with modified b-CDs, the stability con-
ꢁ1
The profile showed that hydrolysis of SPG was significantly stant with HP-b-CD was found to be comparable (911 M
)
accelerated above pH 7.0. SPG hydrolysis occurred at pH to that with b-CD, while the SPG/DM-b-CD complex
between pKa1 (3.74) and pKa2 (8.45) of SPG. Therefore, the demonstrated a remarkably high stability constant of

January 2010
47
Fig. 3. Phase Solubility Diagram of SPG/CD Systems at 25 °C
(a) ꢃ, a-CD; ꢁ, b-CD; ꢂ, g-CD. (b) ꢁ, b-CD; ꢄ, HP-b-CD; ꢅ, DM-b-CD; ꢆ, SBE-b-CD.
Table 1. Stability Constants (Kꢃ) of SPG/CD Complexes in 0.10 M HCl at
5 °C
2
ꢁ
1
CD
Kꢃ (M )
a-CD
62.8
877
612
911
30700
—
b-CD
g-CD
HP-b-CD
DM-b-CD
SBE-b-CD
ꢁ1
3
0700 M (Table 1). SBE-b-CD also markedly increased
SPG solubility, but the stability constant could not be calcu-
lated by Eq. 2 because the slope of the graph was greater
than unity. This suggested contribution of the SBE moiety
for SPG solubilization or the formation of a higher order
complex between SBE-b-CD and SPG.
Fig. 4. Effect of CD/SPG Molar Ratio on Apparent First-Order Rate Con-
stant of SPG Hydrolysis at 50 °C and pH 7.0
ꢁ
, b-CD; ꢄ, HP-b-CD; ꢅ, DM-b-CD; ꢆ, SBE-b-CD. The broken line represents the
level for the CD free system.
Variation in SPG Hydrolysis Behavior Relative to b-CD
Additions Hydrolysis behavior of SPG at 50 °C was stud- Table 2. Apparent First-Order Rate Constants for SPG Hydrolysis in the
ied in a buffer solution (pH 7.0) containing different amounts
Presence of CDs at Various Temperatures and pH 7.0
of modified b-CDs (SPG : CDꢄ1 : 5.0, 1 : 50, and 1 : 500
ꢁ
3
ꢁ1
Apparent rate constant (ꢀ10 min
at 25 °C at 37 °C at 50 °C
SPG : CD ratio 1 : 5.0 1 : 50
)
molar ratios) (Fig. 4). For b-CDs at 1 : 500 ratio, the reaction
was not completed due to low aqueous solubility of b-CD.
Among the CDs, SBE-b-CD or DM-b-CD demonstrated
an excellent stabilizing effect against SPG hydrolysis. Espe-
cially when excess amounts (1 : 500) were added, the hydrol-
ysis rate in the system containing SBE-b-CD and DM-b-CD
was found to be about 1/6 and 1/3 that without CD addition,
respectively. Taken together with the phase solubility results
1 : 5.0
1 : 50
1 : 5.0
1 : 50
b-CD
0.89
0.81
0.72
0.72
0.91
0.79
0.49
0.32
4.1
3.8
3.5
3.4
3.9
3.2
2.7
1.5
20
18
15
15
17
17
12
9.0
HP-b-CD
DM-b-CD
SBE-b-CD
ꢁ1
showing a large stability constant (30700 M ) for the
SPG/DM-b-CD complex, the stable molecular interaction of
SPG with CDs appear to play an important role in the chemi-
cal stabilization of SPG in solution.
To investigate the effect of temperature, apparent first-
order rate constants of SPG hydrolysis at pH 7.0 were evalu-
ated at 25, 37 and 50 °C for 1 : 5.0 and 1 : 50 molar ratios
(
SPG : CD) (Table 2). While the activation energies of the
SPG/DM-b-CD (1 : 5.0 and 1 : 50) and SPG/SBE-b-CD
1 : 5.0) systems were comparable with that without CD addi-
(
tion, only the SPG : SBE-b-CD system at 1 : 50 ratio showed
a relatively high activation energy (108.9 kJ/mol). This result
seems to be due to the difference in interacting mode of SPG
with DM-b-CD and SBE-b-CD from that with the other
CDs. Figure 5 shows the Arrhenius plots for each system and tios
Fig. 5. Arrhenius Plot for SPG Hydrolysis at Various CD/SPG Molar Ra-
activation energies (E ) listed in Table 3 were calculated with
(a) DM-b-CD, (b) SBE-b-CD. Molar ratio: ꢀ, 0; ꢁ, 5.0; ꢂ, 50.
a

4
8
Vol. 58, No. 1
2
ꢁ1
R ꢆ0.997.
interaction, validating the high stability constant (30700 M )
NMR Studies in the SPG/DM-b-CD and SPG/SBE-b- estimated from the phase solubility diagrams of the
CD Systems The molecular interaction of SPG with DM- SPG/DM-b-CD system. Moreover, the stability constant of
1
b-CD and SBE-b-CD was investigated using H-NMR and the SBE-b-CD system was found to be larger than that of
2
D-NMR spectroscopy. Based on Eq. 1, the dissociation con- SPG/DM-b-CD, suggesting that SBE-b-CD further stabilizes
stants of SPG/CD complexes were calculated from the chem- SPG against hydrolysis.
ical shifts on the NMR spectra of each system containing
various concentrations of CD. For the DM-b-CD and SBE-b- vestigated using 2D-NMR spectroscopy. After signal as-
CD systems, the dissociation constants were approximately signment of chemical shifts, correlation signals in the
Interaction modes of SPG/DM-b-CD complexes were in-
19)
9
0 mM and 30 mM, respectively, which were converted into ROESY spectrum were analyzed to identify the conforma-
ꢁ1
ꢁ1
stability constants (Kꢃ) of 11000 M and 33000 M , respec- tional relationship of two vicinal protons between SPG and
tively. These values were determined to be sufficient for CD DM-b-CD (Fig. 6a). In the ROESY spectrum, correlation
signals were observed between the H5ꢃ proton located in the
Table 3. Activation Energy for SPG Hydrolysis in the Presence of CDs
DM-b-CD cavity and the aromatic protons (H3, H5, H6, and
H7) of the benzene ring on the edge of the SPG molecule.
The H3ꢃ proton also located in the CD cavity showed strong
Ea (kJ/mol)
SPG only
97.8
97.9
101.5
98.7
correlation signals with the methylene chain (H8 and H9)
and benzene ring (H3 and H5) protons of SPG. Furthermore,
both the H6ꢃ and 6ꢃ-O-methyl protons of DM-b-CD, located
on the side of the narrow opening of its torus, indicated cor-
relation signals with the H3, H6 and H7 protons of SPG for
SPG : DM-b-CD (1 : 5.0)
SPG : DM-b-CD (1 : 50)
SPG : SBE-b-CD (1 : 5.0)
SPG : SBE-b-CD (1 : 50)
108.9
Fig. 6. 2D-ROESY Spectra of SPG/CD Complexes in D O at 20 °C
2
(a) SPG/DM-b-CD complex. (b) SPG/SBE-b-CD complex.

January 2010
49
Fig. 7. Interaction Mode between SPG and CDs Based on Cross Peak Signals on the ROESY Spectra
(a) Protons considered to be close in space to SPG protons based on correlation signals. Bold and underlined letters represent protons derived from the CD and SPG molecule,
respectively. (b) Possible interaction mode with DM-b-CD.
Fig. 8. Interaction Mode between SPG and CDs Based on Cross Peak Signals on the ROESY Spectra
(a) Protons considered to be close in space to SPG protons based on correlation signals. Bold and underlined letters represent protons derived from the CD and SPG molecule,
respectively. (b) Possible interaction mode with SBE-b-CD.
all combinations. Based on these results, the main molecular H3, H5, H6, and H7; in the middle, H14) were observed on
interaction mode in the SPG/DM-b-CD complex was deter- the ROESY spectrum (Fig. 6b) as those observed in the DM-
mined as follows: (1) the aromatic ring on the SPG molecu- b-CD system, but no correlation signals were observed for
lar edge is inserted within the DM-b-CD cavity at the wide the protons (H8 and H9) on the methylene chain of SPG.
opening of its torus, and (2) the methylene chain of SPG is However, protons within the SBE substituted groups of SBE-
inserted deeply into the DM-b-CD cavity, showing complete b-CD showed correlation signals with several protons on the
inclusion. Moreover, only the correlation signal between the SPG molecule (H3, H5, H6, H7, H12, H13, H14, H17, H21,
H3ꢃ proton of DM-b-CD cavity and the aromatic protons H22), suggesting that the SBE groups stabilize the inclusion
(H12, H13, H14, and H15) of the benzene ring in the middle complex through cooperative interaction. Taken together, the
of the SPG molecule were also observed, suggesting another molecular interaction mode in the SPG/SBE-b-CD complex
possible interaction mode in which the benzene ring in the was determined as follows: (1) the aromatic ring on the SPG
middle of the SPG molecule is partially inserted in the DM- molecular edge is inserted in DM-b-CD cavity; (2) the ben-
b-CD cavity (Fig. 7b). Since some relatively strong correla- zene ring in the middle of SPG may also be partially inserted
tion signals were also observed among the protons of the hy- in the DM-b-CD cavity; and (3) the SBE groups coopera-
drophobic portions of SPG, molecular interactions especially tively interact with SPG (Fig. 8b). Moreover, the ROESY
hydrophobic ones may occur between SPG molecules (Fig. spectrum of the SPG/SBE-b-CD complex also suggested
7
a).
As precise assignment of NMR chemical shifts could not in the case of the SPG/DM-b-CD complex (Fig. 8a).
be determined for the SPG/SBE-b-CD complex, due to non- While marked stability of the SPG inclusion complex with
molecular interactions between the SPG molecules as found
uniform substituted positions of the SBE side chain to the both DM-b-CD and SBE-b-CD was demonstrated, SBE-b-
CD ring, the ROESY analysis for SPG/SBE-b-CD interac- CD at high concentration (SPG : SBE-b-CDꢄ1 : 500) more
tion was performed by assuming that the chemical shifts of effectively suppressed SPG hydrolysis compared to DM-b-
the protons located in the SBE-b-CD cavity (H3ꢃ and H5ꢃ) CD. This greater suppression on SPG hydrolysis could be a
were almost the same as those of DM-b-CD (Fig. 6b). In the result of the cooperative interaction of the SBE side chains
SBE-b-CD complex, similar correlation signals between the with the SPG molecule inserted in the CD cavity.
protons in the SBE-b-CD cavity (H3ꢃ and H5ꢃ) and the aro-
matic protons of SPG (benzene ring on the molecular edge,

5
0
Vol. 58, No. 1
Conclusion
136 (2006).
3
)
Hashizume H., Kawakami M., Yoshida M., Okada M., Enyo Y., Ino-
mata Y., Spine, 32, 315—320 (2007).
Hong Y., Ji H., Wei H., Pain, 124, 27—33 (2006).
Serata K., Ikeda T., Iida Y., Okuni H., Tomaru T., Serotonin(5-HT2)
Kenkyukai Houkoku, 34—35 (1997).
Possible applications of CDs were investigated for improv-
ing solubility and stability of SPG. The phase solubility dia-
grams demonstrated that both DM-b-CD and SBE-b-CD,
which can effectively solubilize SPG, may be used as solubi-
lizing agents in the preparation of external formulations.
While addition of either DM-b-CD or SBE-b-CD improves
the chemical stability of SPG in aqueous solution, DM-b-CD
may not be appropriate for clinical use due to its hemolytic
4
5
)
)
6) Serata K., Ikeda T., Iida Y., Okuni H., Tomaru T., Serotonin(5-HT2)
Kenkyukai Houkoku, 33 (1998).
7)
Takaoka T., Hayashi Y., Hatano K., Sekiya Y., Serotonin(5-HT2)
Kenkyukai Houkoku, 16—17 (1996).
Hanawa T., Nakazawa M., Mohri K., Ito, A., Tsuchiya T., Suzuki M.,
Hanawa K., Kawata K. Nakajima S., J. Pharm. Sci. Technol. Jpn., 60,
175—182 (2000).
8)
20)
activity. Therefore, SBE-b-CD appears to be the most suit-
able solubilizing agent for SPG external preparation.
1
9) Hanawa T., Kasai I., Mohri K., Ito, A., Tsuchiya T., Suzuki M.,
Phase solubility diagram and H-NMR analyses demon-
Hanawa K., Kawata K. Nakajima S., Yakugaku Zasshi, 120, 1209—
strated a quite stable inclusion complex of SPG and SBE-b-
CD. 2D-NMR results suggested that the complex exists in
two interaction modes: complete inclusion of the edge-side
aromatic ring of SPG and partial inclusion of the middle ben-
zene ring both within the SBE-b-CD cavity. In addition, the
SBE group appears to cooperatively interact with the SPG
moiety. Consequently, the marked stability of the SPG–SBE-
1
216 (2000).
1
0) Yamazaki M., Unezaki S., Hosoda J., Ousaka Y., Suzuki K., Satoh S.,
Kominato H., Itoh A., Kawata K., Tezuka H., Suzuki M., Nakajima S.,
Hanawa T., J. Pharm. Health Care Sci. Jpn., 28, 22—27 (2002).
1) Hanawa T., Masuda N., Mohri K., Kawata K., Suzuki M., Nakajima S.,
Drug Dev. Ind. Pharm., 30, 151—161 (2004).
1
1
2) Anplag Drug Interview Form, ver.10, Tanabe-Mitsubisi Co., Inc.,
2
006.
b-CD complex was considered to result from these molecular 13) Shao Z., Krishnamoorthy R., Mitra A. K., Pharm. Res., 9, 1157—1163
(
1992).
4) Shao Z. Z., Li Y. P., Mitra A. K., Eur. J. Pharm. Biopharm., 40, 283—
88 (1994).
1
1
interactions, and these interactions modes could play an im-
portant role in depression of hydrolysis for ester part of SPG
molecule.
1
2
5) Irie T., Uekama K., Adv. Drug Deliv. Rev., 36, 101—123 (1999).
6) Loftsson T., Jarho P., Masson M., Jarvinen T., Expert Opin. Drug
Deliv., 2, 335—351 (2005).
7) Zerbe O., BioNMR in Drug Research, 2003, 309—319.
8) Higuchi T., Connors K. A., Adv. Anal. Chem. Instrum., 4, 117—212
Acknowledgements We would like to thank CyDex Pharmaceuticals,
®
Inc. for providing sulfobutylether b-CD (SBE-b-CD, Captisol ) to conduct
1
1
this project. We also thank Mr. Takayuki Furuishi, Dr. Toyofumi Suzuki and
Professor Kazuo Tomono of College of Pharmacy Nihon University for their
kind advice of NMR measurement.
(
1965).
1
9) Hara T., Hirayama F., Arima H., Yamaguchi Y., Uekama K., Chem.
Pharm. Bull., 54, 344—349 (2006).
0) Irie T., Kuwahara S., Otagiri M., Uekama K., Iwamasa T., J. Pharma-
cobio-Dyn., 6, 790—792 (1983).
References
2
1
2
)
)
Nishiyama T., Eur. J. Pharm., 516, 18—22 (2005).
Sasaki M., Obata H., Kawahara K., Saito S., Goto F., Pain, 122, 130—