Note: Descriptions are shown in the official language in which they were submitted.
~01~343Z
This invention relates to a stannous-phosphate
complex and its preparation as well as its use in a kit for ~;
forming a bone seeking complex with technetium-99m.
This application is a divisional application of
Canadian Patent Application Ser. ~o. 179,088, filed
August 17, 1973.
It has been known for some time that phosphates,
including long chain linear polyphosphates, when introduced into
the blood stream of mammals will selectively seek out and
collect in the bone or skeletal structure. Pro. Soc. Exp,
Biol. Med. Volume 100, pages 53-55 (1959), Journal of Labelled
Compounds, April-June 1970, Vol. VI, No. 2, pages 166-173,
~ournal of Nuclear Medicine, Vol. 11, No. 6, pages 380-381,
1970, Journal of Nuclear Medicine, Vol. 1, No. 1, January 1960,
pages 1-13. In these cases a phosphorous atom or atoms of the
phosphate are radioactive, i.e. 3 P. ;~
It has also been known for some time that technetium-
99m (99mTcj is a preferred radionuclide for radioactively scan-
ning organs because of its short half life and because it
20 radiates gamma rays which can be easily measured, compared, ~or
example, to beta rays. See Radiology, Vol, 99, April 1971,
pages 192-196.
It has also been known for some time to use divalent
stannous tin (Sn++) in the form of stannous chloride, or di-
valent iron (Fe+ ) or reduced zirconium to bind radioactive
99mTc to carriers, such as chelating agents, red blood cells,
albumin and other proteins, which selectively seek out certain
~ organs of the body, in order to carry the 99mTc with them to
i~ such organs of the body where it is concentrated, whereby such
organ can be radioactively scanned or imaged for diagnostic or
other purposes, e.gO radioactive treatment of a pathological
- ..... , :..... . . : ,. . .
,. . ., :
:~l [)8V~3;~:
condition. See Journal of Nuclear Medicine, Vol. 11, ~o. 12,
1970, Page 761, Journal of Nuclear Medicine, Vol. 12, No. 1,
1971, pages 22-24, Journal of Nuclear Medicine, Vol. 13, No~ 2,
1972, pages 180-181, Journal of Nuclear Medicine, Vol. 12, No.
5, May 1971, pages 204-211, Radiology, Vol. 102, January 1972,
pages 185-196, Journal of Nuclear Medicine, Vol. 13, No. 1,
1972, pages 58-65.
Also, it has been sugges-ted to label a stannous com-
pound with 99mTc for radioactively imaging bone marrow, Journal
of Nuclear Medicine, Vol. 11, 1970, pages 365-366.
It has also been known for some time that the stannous
ion Sn~+ forms soluble complexes with long chàin polyphosphates,
Journal Inorganic ~uc. Chem., Vol 28, 1966, pages 493-502.
It has been suggested to employ the aforesaid 9mTc
for radioactively scanning the skeletal bone structure of
mammals by complexing or binding it to tripolyphosphate carrier
by use of the aforesaid stannous ion as a binding agent in order
for such phosphate to selectively carry the 99mTc to, and con-
centrate it in, the skeletal bone structure upon in vivo
intravenous administration for subsequent radioactive scanning
or imaging the skeletal structure. Radiology, Vol. 99, April
1971, pages 192-196. The use of 9 mTc in this manner is alleged
to have certain advantages over the use of strontium, e.g. 85Sr,
as the radioactive label which has been used for radioactive
bone scanning in the past. These advantages are those which are
inherent in mTc, i.e. short half life and pure, near optimal
energy gamma rays. However, the bone uptake (the percent of the
total dosage which becomes concentrated in the skeletal
structure within a certain time after in vivo intravenous
administration) of such 99mTc-containing complex and the ratios
of such bone uptake to uptake of the mTc by the other organs
.
.. . -: , : ~ - ~
~08~432
of the body (the higher these ratios the better), i.e. radio-
active contrast, are not nearly as high as with radioactive
strontium.
It has been discovered that if the phosphate moiety
of the 99mTc-stannous-phosphate complex, which has been suggested
in the aforesaid Radiology publication, comprises pyrophosphate
(P207 ) (which is a linear polyphosphate moiety of molecular
weight less than 300), the bone uptake, bone/blood ratio, bone/
liver ratio, bone/G.I. ratio and bone/kidneys ratio are sub- ;
stantially increased.
It has also been discovered that optimum results are
achieved if such phosphate moiety contains no more than about
15 to 20 or 25%~ preferably no more than 5 to 10~/o and more
preferably no more than 5% (less than 5% is the most preferred),
by weight of linear or branched chain polyphosphate (formula
PnO3n+l (n~2)) of molecular weight greater than that of pyro- ~
phosphate. ~ -
Maximum bone/liver ratios are achieved when the
99mTc-Sn +-pyrophosphate complex is administered to the mammal
in relatively small dosages of substantially less than 20 or 25
preferably substantially less than 8 or 10 and still more pre-
ferably less than 5 or 6 (between 0.01 or 0.10 and 3 and even ;~
less provide excellent results), milligrams pyrophosphate
moiety per kilogram of body weight of the mammal.
The term "phosphate moiety" as used herein refers tothe phosphorus and oxygen atoms only of the phosphate.
The presence of polyphosphates of formula PnO3n+l (n~2)
and molecular weight greater than that of pyrophosphate seems
to reduce bone take-up and the aforesaid ratios, as compared
to complexes without such higher molecular weight polyphosphates.
However, as aforesaid, some of such higher molecular weight
- 3 ~
.
-;. ., : ~
~L~8~43Z
polyphosphates can be tolerated, preferably not more than
about 15% to 2~/o or 25%~ more preferably no more than 5% to
l~/o and still more preferably not more than 5% (less than 5% is
the most preferred), by weight of the total phosphate moiety.
Where the pyrophosphate does not constitute 10~/o of
the phosphate moiety of the 99mTc-Sn++-phosphate complex, the
rest of the phosphate moiety is preferably a ring phosphate of
formula Pn03n n (with n preferably being 3 which is trimeta-
phosphate) and/or ortho phosphate, and preferably a ring
phosphate only, although the a-foresaid limited amounts of higher
molecular weight linear polyphosphates can be tolerated.
The complex is made from a water soluble alkali metal ~`
(preferably sodium) or ammonium salt or acid salt of the pyro-
phosphate, e.g. sodium pyrophosphate.
Preferably, the sodium pyrophosphate is admixed with
a stannous salt, e.g. SnC12 (the stannous salts of other acids
which are pharmaceutically acceptable, i.e. safely intravenously
administered, can be used) to form the stannous-pyrophosphate
complex, the pH of which is adjusted to 3-8, preferably 5-8, by
20 a pharmaceutically acceptable acid, such as HCl, or base, such
as NaOH or Na2CO3 or NaHCO3, followed by admixing with the
stannous-pyrophosphate complex, an aqueous saline solution of
radioactive sodium pertechnetate ( mTc) to form the mTc-
stannous-pyrophosphate complex at the time it is desired to
intravenously administer the 9 Tc complex. The stannous-pyro-
phosphate complex may be sealed in a sterile, non-pyrogenic
container or vial as a solution or a lyophilized solid and shipped
as a ]~it with the freshly generated sterile and non-pyrogenic
99mTc being added aseptically at the situs just prior to use.
.. ~ , . . :.:
ilO~ 3;~
According to the invention there is provided a method
o~ making stannous-pyrophosphate complex comprising admixing a
solution of a water soluble phosphate salt or acid salt having
a pharmaceutically acceptable cation, the phosphate moiety of -~
which comprises pyrophosphate with stannous compound to form
the complex, and adjusting the pH of the complex to between 3
and 8 with a pharmaceutically acceptable pH adjusting agent,
the weight ratio of 3tannous to phosphate moiety being from 10
to 0.5~ `'
In another aspect of the invention there is provided
a stannous-pyrophosphate complex produced in accordance with
the invention
The stannous compound is conveniently employed in
solid form, for example, as a lyophilizate.
According to another aspect of the invention there
is provided a kit for forming a bone seeking complex with
technetium-99m, comprising a stannou~-phosphate complex sealed
in a sterile, non-pyrogenic container, the phosphate moiety
of the complex comprising pyrophosphate, the weight ratio of
stannous to phosphate moiety ranging from 10 3 to 0.5.
According to yet another aspect of the invention
there is provided a method of making the kit comprising
admixing with a stannou~ compound, a solution of a water
soluble phosphate salt or acid salt, the phosphate moiety of
which comprises pyrophosphate to form a ~tannous-pyrophosphate
complex, adjusting the pH of the complex to between 3 and 8
with a pharmaceutically acceptable pH adjusting agent,
sterilizing the complex and sealing it in a sterile non- :
pyrogenic container, the weight ratio of stannous to phosphate
moiety ranging from 10 3 to 0.5.
: The following compositions were prepared:
B ~ _ 5 _
:~8~3;~
TABLE
Sample No. De~cr~ ion
1 A commercial sodium polyphosphate sold by FMC
Corporation under the trade name FMC Glass H
(average chain length of 21 and average M.W.
about 2100).
1-1 A first high molecular weight fraction of the
FMC Glass H of Sample 1 obtained by fractionating
an aqueou~ solution of Sample 1 with acetone
according to the technique described in Van
Wazer, Phosphorous And Its Compounds, Inter- :
science Publi~hers, Inc. 1961 (pages 744-747) to
'' ':
:
'` ' .
_ 5a-
1C)8~3~32
Sample No . De scr~
precipitate out of the aqueous solution of -the
FMC Glass H, as an oil, the highest molecular
weight fraction of polyphosphates (composition
given in TABL~ 2).
1-2 A second acetone fraction of FMC Glass H
achieved by adding more acetone to precipitate
out of the remaining supernatant of 1-1, as an
oil, the next higher molecular weight poly~
10 ` phosphates (composition given in TABLE 2). The
acetone decreases the solubility of the poly-
phosphates in the water: the higher the mole-
cular weight of the polyphosphate the less
soluble it is so that the highest molecular
weights are forced out of solution first.
1-3 A third acetone frac-tion of FMC Glass H contain-
ing the next higher molecular weight polyphos-
phates is precipitated out of the remaining super-
natant solution of 1-2, as an oil, upon addition
of further amounts of acetone (composition given !
in TABLE 2).
1-4 A fourth acetone fraction of FMC Glass H contain-
ing the next higher molecular weight polyphos-
phates (composition given in TABLE 2) is pre-
cipitated out of the supernatant solution of 1-3,
as an oil, by adding more acetone.
1-5 A fifth acetone fraction of the FMC Glass X (con-
, taining the next higher molecular weight poly-
- phosphates) (composition given in TABLE 2) is
precipitated out of the remaining supernatant
-- 6 --
: ,.;
.. . . . . . .. . . . ...
,. . : . .. . . . .
, ~ . .: ;,
32
Sample No. Description
solution of l-4, as an oil, by adding more ace-
tone.
1-6 A sixth ace-tone fraction of FMC Glass H
(composition given in TABLE 2) is precipitated
out of the remaining supernatant solution of .
l-5, as a solid precipitate of the next higher
molecular weight polyphosphates by adding more
acetone. .. .
1-7 A seventh acetone fraction of FMC Glass H
(composition given in TABLE 2) is precipitated
out of the remaining supernatant solution of
1-6, as a solid precipitate of the next higher
molecular weight polyphosphates by adding more
acetone.
1-8 The residue fraction in the supernatant liquid
left after removal of the 1 7 fraction (com-
position given in TABLE 2) is recovered by
evaporating off the supernatant liquid. .
2 An end acetone fraction of Sample l after 90~/O
by weight had been previously fractionated off :
and leaving after removal of such end fraction
3% by weight in the supernatant (composition
given in TABLE 2).
4 A mixture o-f 86% sodium trimetaphosphate
(Na3P309), 3% sodium orthophosphate (Na3P04)
; (molecular weight of phosphate moiety - 95)
and 10% sodium pyrophosphate (~a4P207) (linear
polyphosphate - molecular weight of phosphate
moiety - 174) obtained by acetone fractionation
8~32
Sample No. D~scription
of sodium trimetaphosphate obtained from
Monsanto. Sodium trimetaphosphate, as aforesaid,
is one of a plurality of cyclic phosphates
having the general formula PnO3 n. Sodium
orthophosphate is a phosphate monomer. Sodium
pyrophosphate is a dipolyphosphate.
An acetone end fraction of a food grade poly-
phosphate sold by FMC under the name FMC FG ~
(composition given in TABLE 2). ~-
6 A commercial cyclic trimetaphosphate sold by
Stauffer Chemical. (Composition given in
TABLE 2).
7 Sodium orthophosphate~ ;
,
8 Sodium pyrophosphate.
9 Sodium tripolyphosphate.
' :' `;
Sodium tetrapolyphosphate - Na6P4013 - a poly-
phosphate - phosphate moiety havin~ a M.~. of 348.
It together with the pyrophosphate and tripoly-
phosphate, fall in the class of linear chain
polyphosphates having the general formula
-(n-~2)
n 3n+1
An aqueous solu-tion of each of the phosphate com-
position samples 1 through 10 ~40 mg. phosphate/l ml. solution)
were made with distilled water in which the dissolved oxygen
content was reduced in a conventional manner by bubbling
through such water gaseous nitrogen for a period of two hours.
The water and phosphates were mixed to form the solutions in a
nitrogen atmosphere and in a nitrogen flushed container. The
- 8 -
:
43;~
reason for this is to reduce oxidation o~ the divalent Sn++ to
be subsequently admixed with each solution sample. However, it
is not essential (but highly preferred) to use nitrogen-
treated water or a nitrogen atmosphere or a nitrogen-flushed
container. Other known pharmaceutically acceptable conditions,
which will inhibit oxidation of the Sn+~ upon subsequent mixing
thereof with the phosphate solution, can be used, including the
use of conventional pharmaceutically acceptable reducing
agents and anti-oxidants in the products used.
Each of these solutions, samples 1 through 10, in an
amount equal to 100 ml, was mixed with 0.16g of solid S~ 12 2H20
under a nitrogen atmosphere. The SnC12 2H20 was made by adding
to 84.5 mg. of metallic tin, sufficient concentrated HCl with
mixing until all the tin has dissolved followed by removing
excess acid and water by lyophilization (this operation also
being carried out in a vacuum or in a nitrogen atmosphere and
in a nitrogen flushed container to prevent oxidation of
stannous to stannic). Antioxidants, which can be administered
intravenously, may also be used. A stannous (Sn~ phosphate
complex or mixture of some kind ~as formed in each case, the
phosphate moiety of each sample corresponding to the phosphate
moieties of the phosphates set forth in TABLE 2.
Sufficient aqueous solution 3N sodium hydroxide
(sodium carbonate or bicarbonate can also be used), in the case
of samples 1 through 7 and 9 and 10, and 3N HCl, in the case of
sample 8, is then added to each sample to give a pH of 5.0 to
achieve a pH suitable for subsequent intravenous in vivo
administration into the body of a mammal, in this case adult
mice. The pH adjustment is preferably done under a nitrogen
atmosphere also.
After thorough mixing, the solutions are sterilized
by passing them through a Millipore*biological filter of 0.22
micron pore size under a nitrogen atmosphere. Thereafter milli-
* trademark
_ 9 _
: - ~ ,: , .:
108~432
liter portions of each of the sterile solutions are poured into
individual sterile and non-pyrogenic storage glass vials under
a nitrogen atmosphere.
In the case of each sample, vials are lyophilized by
conventional freeze drying equipment under aseptic conditions
to remove water. This provides a solid stannous-phosphate
complex which aids in shipping and storage and which is more
stable than the ~omplex in solution.
Each vial contains 1.35 mg. SnC12 and ~0 mg. of the
phosphate.
The vials can be sealed and stored until needed sub-
sequently to form the technetium-99m-stannous-phosphate complex
at the use situs.
To prepare the technetium-99m complex, 3 to 7 (5) ml.
of fresh sodium pertechnetate, removed as a sterile non-pyro- ``
genic eluate from a sterile NEN 99mTc Generator (any other ~`
source of pharmaceutically acceptable 99mTc can be used,
including mTc generators manufactured by other than NEN), in
a 0.9% saline solution is aseptically added to each vial con-
taining the sterile and non-pyrogenic stannous-phosphate com-
plex and the vial is swirled until a solution is obtained. In
each`case a technetium-99m-stannous-phosphate complex or
mixture of some kind is formed in aqueous solution (8 mg.
phosphate per ml solutibn when 5 ml of pertechnetate is used),
the phosphate moiety of which corresponds to the phosphate
moieties of the phosphate compounds of each sample set forth
in TABLE 2.
Aseptic techniques and sterile, non-pyrogenic ingred-
ients and containers were used at all steps, such procedures
being standard to those skilled in the art.
An eleventh sample was prepared in the manner set
forth above by diluting sample 8 to a concentration of 1 mg of
.
-- 10 --
43;~:
phosphate per ml of solution. This was labeled Sample 11.
Each o the technetium-99m-stannous-phosphate complex-
containing solutions is aseptically intravenously injected in
vivo into a vein in the tail of adult mice (average weight
0.040 kgs) in an amount equal to between 1 and 3 mCi and a
volume of 0.12 ml (8 mg. of phosphate per ml solution in
samples 1 through 10 and 1 mg. phosphate per ml. solution in
sample 11). Also sample 8 was injected in the same manner
except that a volume of 0.015 ml was injected instead of 0.12
ml to reduce the dosage of the complex by a factor of ~. This
was labeled Sample 12.
Three hours after intravenous administration, some of
the mice to which each sample was administered were sacrificed
and the various organs of their bodies (skeletal, liver, G.I.,
blood, kidneys) were counted by conventional gamma ray counting
techniques to determine uptake of 99mTc by each organ and
thereby determine contrast of bone uptake as compared to uptake
by the other organs. As aforesaid, it is not only important
to have a high bone uptake (based on total technetium-99m-dosage)
but it is also important that the ratio of uptake by the bone
to uptake by the other organs be high.
The results are set forth in TABLE 2 below, in which
the uptakes (the bone uptake figures represent the average
bone uptake for the skeletal system) are in terms of percent of
the total technetium-99m activity injected (corrected for radio-
active decay) which has collected in the various organs indicated
three hours after in vivo intravenous injection, in which the
ratio amounts are computed from the uptake amounts, in which
"Percent Having Phosphate Moiety M. W. Less Than 300" refers to
weight percent of the phosphate moiety based on the total phos-
phate moiety of the sample identified in the first horizontal
column, in which the percents referred to under Phosphate
3~:
Composition are weight percents of the whole phosphate moiety :
of the sample (as aforesaid, phosphate moiety as used herein
is limited to that part of -the compound or complex made up of
phosphate phosphorus and oxygen atoms), in which Ortho Pl
refers to the phosphate moiety of sodium orthophosphate,
Pyro P2 refers to the phosphate moiety of sodium pyrophosphate,
Tripoly P3 refers to the phosphate moiety o-f sodium tripoly-
phosphate, Tetrapoly P4 refers to the phosphate moiety of
sodium tetrapolyphosphate, Trimeta R3 refers to the phosphate
moiety of sodium trimetaphosphate, Tetrameta R4 refers to the
phosphate moiety of sodium tetrametaphosphate, both trimeta and
tetrametaphosphates falling within the class of cyclic or ring
phosphates having the formula P303n n, in which "Pentapoly and
Longer Linear Chains" refers to the phosphate moiety of sodium
pentapolyphosphate and longer linear (linear as used herein
includes straight and branched linear phosphate chains) poly-
phosphates of formula Pn03rl+l (n+2), in which "Average M.W."
refers to the average molecular weight of the phosphate moiety
of the sample and in which "Fraction In Raw Stock" with
reference to samples 1-1, 1-2, 1-3, 1-4, 1-6, 1-7 and 1-8 refer :
to the normalized percent by weight of each of these samples in
sample 1, which is the raw stock which is fractionated.
- 12 -
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~L~8043Z
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Conventional gamma counting techniques for measuring
techne~ium 99m take-up in ~he organs are conventional gamma ray-
excitable scintillation counters for radioassaying multiple
samples of the organs of the sacrificed mice.
Also, conventional scanning by radioac-tive imaging
using a gamma ray-excited scintillation or gamma camera and a
dual crystal rectilinear scanner was used in vivo. In vivo
scintiphotos of the total body using the Anger camera were
obtained as well as rectilinear total body scans.
The figures given in TAsLE 2 are average figures
achieved by the aforesaid conventional counting techniques,
each sample having been intravenously administered to mice
followed by radioactive counting.
Following intravenous administration, the Tc-Sn++-
pyrophosphate complexes of the present invention are rapidly
cleared from the blood by deposition in bone and excretion into
urine. Thus, the technetium-99m-stannous-pyrophosphate
complexes are metabolizable. The deposition of the 99mTc-
stannous-pyrophosphate complexes of the invention appears to be
; 20 primarily a function of the bone blood flow as well as being
related to the efficiency of the bone in extracting the complex
from the blood which perfuses the bones.
It was observed that the deposition of the 99mTc in
the skeleton is bilaterally symmetrical with increased
accumulations being present in the axial skeleton as compared to
the appendicular skeleton. There is also increased deposition
in the distal aspect of long bones.
Localized areas of abnormal accumulation of the radio-
pharmaceutical may be seen in primary malignancies of the bone,
metastatic malignancies of the bone, acute or chronic osteo-
myelitis, arthritides, recent fractures, areas of ectopic
calcification, Paget's disease, regional migra-tory osteoporosis,
-.~
- 15 ~
,. . ~ . . . .
L3Z
areas of aseptic necrosis and in general any pathological
situation involving bone in which there is increased osteogenic
activity or localized increased osseous blood perfusion.
The acute toxicity level in mice (LD50/30) for Sample
No. 2 has been determined to be lS0 mg/Kg body weight and for
Sample 6 it is 800 mg/Kg and for Sample 8 it is 70 mg/Kg.
Subacute toxicity studies in mice of Sample 2 have shown no
` signs of toxicity after 15 daily injections at dose levels as
; high as 63 mg/Kg body weight/day. A similar subacute study in
dogs indicates no signs of toxicity at a dose level of 3.6 mg/Kg
body weight/day.
It was found that samples 4 and 6 were only one fourth
as toxic to mice as sample 2 and one-eighth as toxic to mice as
sample 1.
The complexes of the invention have been used success-
fully as a skeletal imaging or scanning agent to visualize
areas of altered blood flow to the bone and altered osteogenic
activity, including suspected bone lesions not shown on X-ray,
bone survey performed as part of a work-up in patients with
known or suspected malignancy, to follow the response of meta-
static or primary bone lesions to radiation therapy, metabolic
bone disease, to diagnose arthritis and osteomyelitis, and to
diagnose and determine healing rate of bone fractures.
Seven clinical studies by seven doctors on humans using
sample 2 and involving 91 patients showed no adverse reactions
and were deemed to be highly successful and clinically useful
for skeletal diagnostic purposes in the case of 90 patients.
The technetium-99m (99mTc) labeling reactions involved
in preparing the 99mTc-stannous-phosphate complexes of the
invention~depend on maintaining the tin in the reduced or stan-
nous (Sn+2) sta-te. Oxidants present in the pertechnetate supply
may adversely affect quality.
.
~ - 16 -
~L~8~43Z
The radioactive dosage of the 99mTc complex of the
invention may vary from 1 to 25 mCi (millicuries) but preferably
is from 10 to 15 mCi. The dosage should preferably be sub-
stantially less than 20 or 25, preferably less than 8 or 10 and
more preferably less than 5 or 6 mg. of pyrophosphate moiety
per kilogram of body weight of the mammal since greater pyro- ;
phosphate dosages than this reduces the bone-liver ratio too
much. ~ote for example the low bone-liver ratio in sample 8 '
where the dosage was 25 mg. pyrophosphate per Kg body weight
compared to the bone-liver ratio of sample 11 where the dosage
was 3.1 mg/Kg body weight.
Only trace amounts of pyrophosphate moiety in the
dosage, e.g. as low as 0.001, more preferably 0.01, mg/Kg body
weight, gives good bone take-up and bone-to-other organ take-
up ratios.
The dosage of pyrophosphate can be kept small either
by use of more dilute dosage solutions of the pure pyrophosphate,
as in sample 11 or by administering smaller doses of a more con-
centrated complex solution, the phosphate moiety of which con-
tains a high concentration of pyrophosphate or by more con-
centrated solutions of phosphate containing, in addition to -the
pyrophosphate, ring phosphate and/or orthophosphate which
effectively dilute the pyrophosphate concentration of the dose.
It is preferred to use a 9mTc--Sn ~-phosphate
` solution containing between 0.1 and 40, more preferably between
0.5 and 4 or 5 mgs of pyrophosphate moiety per ml of solution.
,~ An advantage of a complex containing a relatively
~' large amount of ring phosphate and a smaller amount of pyro-
,
phosphate is that the ring phosphate in addition to providing
~ 30 excellent~,;bone up-take and bone-to-other-organ ratios is less
-~ toxic than pyrophosphate, although pyrophosphate, alone, is
, still not unduly toxic.
- - 17 -
32
Scanning may be commenced as early as one hour after
intravenous administration and may be as long after injection ;~
as clinically useful amounts of Tc remain in the organ. -
Another manner of making the complex of the invention ~ :
- is to weigh 4 mg t of SnC12 2~I20 and 100 mg. of sodium pyro-
phosphate into a flask (the flasX is sterile and non-pyrogenic - -~
.` and is flushed with nitrogen before weighing and is kept under
. .
nitrogen during this step and for the next step). Add, under
aseptic conditions, 12 ml of sterile, non-pyrogenic sodium
`~ 10 pertechnetate in 0.9% saline solution. Shake the mixture until
a solution is obtained followed by intravenous injection (pre- ~:
ferably the pH of the mi~ture is aseptically adjusted to pH `~
`~` 3-8 before intravenous injection). ~ .
, Also, the sterile stannous chloride can first be ~ ~
:~ aseptically mixed with the sterile 99mTc saline solution to : ;
form a mTc-stannous complex, followed by adding the sterile
sodium pyrophosphate under aseptic conditions to form the
99mTc-stannous-pyrophosphate, adjusting the pH to 3-8, followed
by intravenous in]ection.
It can be seen from TABLE 2 that a 9mTc-stannous-
phosphate complex in which the phosphate moiety comprises pyro-
phosphate and in which such rnoiety contains no more than 25% by
weight of linear polyphosphate of molecular weight greater than .
that of pyrophosphate (sarnples 1-7, 1-8, 2, 4, 5 and 6, 8, 11
and 12) gives surprising higher bone uptake and ratio of bone
uptake to other organs, as compared to orthophosphate and other
polyphosphates, e.g. tripolyphosphate, tetrapolyphosphate and
longer chain polyphosphates (see samples 1, 1-2 to 1-6, 7, 9 ~.
and 10).
I-t can also be seen by comparing samples 8, 11 and 12
in TABLE 2 that the bone to liver ratio is substantially increased
by reducing the amount of pyrophosphate in the dosage admlnistered
- 18 -
- ~80~3Z
to the mammal.
The pyrophosphate moiety of the 99mTc-stannous-
phosphate complex may be from l or 2% or even less up to 100%
by weight of the total phosphate moiety. Preferably, the pyro-
phosphate moiety consists of 5 or 10% or more of the total
phosphate moiety, more preferably 5~/O or 60% or more and most
:: .
preferably between 90 and 10~/o.
Although the stannous (Sn +) ion is by far preferred,
~ the divalent ferrous (Fe++) ion in the form of ferrous ascor-
; lO bate, and reduced zirconium can also be used but without as
: good results. All these metals can exist in a plurality of
redox states.
The phosphate may be added to the solid SnC12 as an
aqueous solution, or it may be added to a solution of the SnCl2
to form the Sn -phosphate complex followed by adding the 99mTc
solution.
Very little Sn~+ need be used to form the complex of
; the invention, e.g. less than 7 or 10~/o of the phosphate based on '
molecular weights,
The weight ratio of Sn + ion to the pyrophosphate
moiety may vary over a wide range, i.e. from lO 3 to 0.50, pre- `~
ferably 0.01 to 0.4. It is preferred that the molecular ratio
of Sn + to pyrophosphate moiety not exceed 2/l. The maximum
ratio is dictated by the amount beyond which the precipitation
of Sn occurs. The minimum amount required is that amount
necessary to bind a sufficient amount of 99mTc to the pyrophos-
phate to achieve good bone uptake and contrast. This can be
determined by routine experiment.
The pH of the stannous-phosphate complex may be
between 3 and 8.
The water used-for making the complexes of the
invention is distilled and is at an elevated temperature of
- 19 -
3'~
200~F during removal of dissolved oxygen and reduction of
oxidants by bubbling the nitrogen gas therethrough.
The maximum amount of99mTc is that beyond the
` capacity of the Sn~-pyrophosphate complex to bind the 9mTc.
This can be determined by routine thin layer radiochromatography
to determine the percent of free or unbound mTc in the
complex. The minimum amount is dictated by that amount below
which there is an insufficient amount to give good scanning
of bone uptake and contrast, which also can be determined by
routine experiment. Generally, the amount of 9 ~ c added to
the Sn++ pyrophosphate complex should be sufficient to achieve
the counting rate desired by the doctor or laboratory personnel
~ , .
~;~ for the volume to be injected, ordinarily, as aforesaid, the
activity dosage varies from 5 to 25 millicuries.
Although sodium pyrophosphates are preferred, any
`~ alkali metal, such as potassium and lithium, or ammonium can
be used as the cation so long as it is pharmaceutically accept-
able so that it can be safely administered intravenously. Also
~`~ the acid pyrophosphates of such cations can be used.
; 20 Although in the examples given above saline water was
used as the vehicle, any other vehicle which is pharmaceutically
acceptable for intravenous administration can be used.
It is not intended that the invention be limited to
any theory which may have been given above or to the specific
examples set forth above but only by the claims appended hereto
and their equivalents.
:,
- 20 -
.
