A new salt, metformin clofibrate, is disclosed. This salt has useful therutic properties and can be used in the control of glycaemia and cholesterolaemia and in the treatment of atheromatous conditions.

The present invention relates to the metformin salt of clofibric acid. 
(Clofibric acid is also known as 2-p-chlorophenoxy-2-methyl-propionic 
acid, and metformin is the biguanide, 1,1-dimethylbiguanide.) It also 
relates to a process for the preparation of this salt and its application 
in therapy. 
Metformin clofibrate according to this invention is metformin 
monoclofibrate and is represented by the formula: 
##STR1## 
This salt can be prepared from metformin and clofibric acid by a method 
which is in itself known. 
Since the free base of metformin is not commercially available, it is 
preferred, according to the process of this invention, to use metformin 
hydrochloride as starting material. According to this preferred process, 
metformin hydrochloride, dissolved in a lower alcohol, especially methanol 
containing 2% by volume of water, is contacted with an anionic resin in 
order to obtain metformin base. Metformin base is then contacted with 
clofibric acid in acetone to produce the salt of this invention.

A preparative Example which serves to illustrate the invention is given 
below. This Example illustrates the manufacture of approximately 5 kg of 
metformin monoclofibrate. 
EXAMPLE 
The equipment consists of: 
Tanks for preparing and storing the solutions, 
A 40 liter column (useful height: 1.50 m), 
A 150 liter reactor and 
The customary filtration and drying equipment. 
The starting materials consist of: 
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metformin hydrochloride 
3,000 g(18.1 mols) 
clofibric acid 3,885 g(18.1 mols) 
methanol 242 l 
acetone 100 l 
an aqueous solution of sodium 
hydroxide of concentration 40 g/l 
100 l 
demineralised water 
500 l 
anionic resin (Duolite A 101 D) 
25 kg. 
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The resin is introduced into the column, using demineralised water, and 
regenerated (because commercially available Duolite A 101 D resin is in 
the chloride form) by passing the sodium hydroxide solution through and 
then rinsing with demineralised water until the eluate becomes neutral 
(approximately 400 liters of demineralised water have to be used). The 
column is then rinsed with 100 liters of methanol containing 2% by volume 
of water, this having proved to be the best exchange solvent. 
The metformin hydrochloride is dissolved in 82 liters of methanol 
containing 2% by volume of water and the solution thus obtained is passed 
over the resin. The chloride content of the eluate collected is checked to 
ensure that it is .ltoreq. 50 ppm relative to the solution. 
The column is then rinsed with 60 liters of methanol containing 2% by 
volume of water and the resulting eluate is combined with the above 
eluate. The total eluate is 142 liters of a solution of metformin base. 
The total eluate is concentrated to dryness in vacuo and at an external 
temperature of 40.degree. C, which can rise to 60.degree. C at the end of 
the concentration process so as to remove the water completely. 
When all the solvent is removed, metformin base solidifies in the form of a 
light yellow solid (theoretical yield of the order of 99%). This dry 
metformin base can be converted immediately into a salt when contacted 
with clofibric acid; before the step of converting it to a salt, it can 
still contain 1% (by weight) of metformin hydrochloride without subsequent 
disadvantage. The methanol is recovered from the distillate. 
The resin is rinsed with 100 liters of demineralised water and the 
entrained methanol is recovered by this rinsing process. At this stage, 
the column is ready for a further operation, beginning with the 
regeneration process. 
The metformin base, in the concentration reactor is dissolved in 100 liters 
of acetone, with stirring. A small amount of coloured insoluble material 
(consisting mainly of unrecovered metformin hydrochloride) which may be 
present is filtered off and clofibric acid in the solid state is 
immediately added to the filtrate, with stirring. 
The clofibric acid dissolves as the metformin clofibrate crystallises out 
(it can happen that this crystallisation takes place before the acid has 
completely dissolved; this does not have any subsequent effects). Stirring 
is continued for 4 hours after the start of crystallisation. 
The solution containing the metformin clofibrate which has been formed is 
stored in a cold chamber. 
The solution is then filtered to collect the metformin clofibrate formed, 
followed by rinsing using 4 times 5 liters of chilled acetone and maximum 
suction-drying. The acetone is recovered from the filtrate, and the 
metformin clofibrate is dried in a ventilated oven set at 40.degree. C. 
5 Kg, or a little more, of metformin clofibrate, in the form of a white 
crystalline powder, are thus obtained, corresponding to a total yield of 
approximately 80% relative to the theoretical amount calculated from the 
stoichiometric amounts of metformin hydrochloride and clofibric acid 
employed. If care is taken partially to concentrate the solution of 
metformin base in acetone (for example, by removing approximately 15 
liters of acetone therefrom) in vacuo at ambient temperature, the yield 
can be increased to 90 - 95%. 
The melting point of metformin clofibrate is 165.degree. C (as measured in 
a capillary tube). 
From the physical point of view, this salt, which can only be anhydrous 
initially, has a melting point that is different from that of clofibric 
acid (120.degree. C as measured in a capillary tube) and from metformin 
base (110.degree. C as measured in a capillary tube). 
The infra-red spectrum is different from that of the spectra of clofibric 
acid, metformin base and the equimolecular mixture of clofibric acid and 
metformin base. The infra-red spectrum demonstrates that a salt has been 
formed because the peaks at 2,700, 2,500, 1,600 and 1,300 cm.sup.-1 of the 
free COOH group of clofibric acid and the peak at 1,320 cm.sup.-1 of 
metformin base do not appear in the case of the salt. 
Taking account of the analytical results, there is considerable evidence 
that the salt obtained according to the invention is metformin 
monoclofibrate, that is to say the equimolecular salt. 
Finally, metformin clofibrate is soluble in cold water (1 g in 5 ml of 
water) and gives solutions with a pH close to neutral. This salt is also 
very soluble in methanol and ethanol. It is sparingly soluble in acetone 
(1 g in 100 ml) at ambient temperature, and insoluble in benzene, 
chloroform and hexane. 
The results of pharmacological experiments have shown that the salt of this 
invention possesses advantageous properties different from the sum of 
those of clofibric acid and metformin. In relation to the toxicity, the 
following values were obtained in mice of the Swiss strain: 
Ld.sub.50 by oral administration: 1.60 g/kg 
Ld.sub.50 by intraperitoneal administration: 0.85 g/kg 
The salt of this invention possesses a hypoglycaemia-inducing action on 
alloxan-diabetic rabbits. In relation to the 
hypocholesterol-aemia-inducing action, an improvement in the lipid 
deposits has been observed in rabbits receiving a 
hypercholesterol-aemia-inducing diet and in genetically diabetic obese 
mice, this improvement being marked at the arterial level. 
The salt of this invention thus makes it possible to control glycaemia 
without the danger of hypoglycaemia occurring, and to treat and prevent 
vascular complications in diabetes. It also makes it possible to treat and 
prevent atheromatous conditions. 
Therapeutic compositions containing metformin clofibrate and a non-toxic 
carrier or diluent are provided by the invention. These compositions will 
preferably be administered orally or parenterally, the daily dose 
depending on whether the patient is, or is not,diabetic. 
If the patient is diabetic, the daily dose is decided in relation to the 
glycaemia. On the other hand, if the patient is not diabetic, the daily 
dose of metformin clofibrate will be 0.5 to 2 g, divided up into several 
doses.