CA2060402A1 - Topical use of calcitonin for the preparation of medications in senile idiopathic cataract and a pharmaceutical composition thereof - Google Patents

Abstract

TITLE:
TOPICAL USE OF CALCITONIN FOR THE PREPARATION OF
MEDICATIONS IN SENILE IDIOPATHIC CATARACT AND A
PHARMACEUTICAL COMPOSITION THEREOF.
ABSTRACT
A new use of calcitonin, as an active principle, is provided for the preparation of topically appliable medications in the treatment of pre-senile and senile idiopathic cataract; and a pharmaceutical composition containing elcatonin as active principle for the preparation of a collyrium.

Description

DESCRIPTION
The present invention relates to the topical use of calcitonin in the therapy of pre-senile and senile idiopathic cataract; and a pharmaceutical composi-tion thereof.
Senile cataract is one of the main causes of sight lowering in all countries and one of the major cau-ses of blindness in developing countries.
Senile cataract is connected with the age of the patient. There are indeed variations in the age of appearance of cataract and in its evolution, depen-ding on the subjects and on geographical places.
Among the main elements of risk there are:
illumination, race, yeographical factors, general health conditions (diabetes, glaucoma, arterial hypertension, lipids metabolism), nutrition, social factors. (B. Lumbroso et al., Records of the Congress: Cataratta ed Età - Rome, 25 Nov. 1989 -pages 27-39).
The exact etiopathogenesis of pre-senile and senile cataract is not known. Among the most accreditated hypotheses there are described, in EP 0213091, three main mechanisms: the oxidation of the struc-tural proteins with the formation of insoluble ag-gregates; the denaturization of the lens proteins ~ ¢~
or the alteration of the lens membrane permeabi-lity.
According to other authors, the cataract pathogene tic mechanism is referable to three groups of hypotheses: khe epithelial, the capsular or the biochemical one.
According to the first hypothesis there is a rela-tionship of cause and effect between an early alteration of the epithelium and a secondary alteration of the fibres.
The biochemical hypothesis explains the opacifi~-a-tion of the len~ with a metabolic alteration con-cerning the lenticular fibres, so that the lenticu-lar proteins being soluble become insoluble by precipitation.
The capsular hypothesis attributes instead the opa-cification of the lens to an alteration of the cap-sular permeability which is reduced for the first and increases for the second.
In summary, one might nowadays affirm that two ap-parently different pathogenetic mechanisms correspond to the two clinical kinds of cataract, the nuclear and the cortical one.
An oxidation of the lenticular proteins occurs in the nuclear cataract, said proteins being soluble ~a~
and gradually becoming insoluble, assuming an am-bergris-like colour.
The ~undamental alteration occurring in the corti-cal cataract is an altered equilibrium of sodium and potassiumcations ~ith an increase in sodium and calcium and a reduction in potassium. (L. Scu]lica, Records of the Congress "Cataratta", Symposium of Taormina, 1989).
It seems that sometimes the pre-senile and senile idiopathic cataract is accompanied by a massive oxidatlon of the SH proteic and non proteic groups of the lens. (M. Testa et al., Exp. Eye Res. 1969, 8, ~47-460).
The existence of a direct correlation between the oxidizing activity of the biological liquids (BLOA~
and the pre-senile and senile cataract has been also stressed. (M. Testa et al., J. of Ocular Phar-macology 1986, 2, 251-266); G. ruliano et al., Pro-ceedings of 3rd Int. Congress of the Intern. Assoc.
for Cataract Related Research, S. Margherita Ligure 1987) o Accordingly it has been postulated that the anti-cataract action of some anti-inflammatory agents (NSAID), such as Bendazac (INN) and Benzydamine (INN), is due to the formation of metabolites (e.g.

benæilic alcohol) able to modify the redox poten-tial of the lens.
The anti-cataract action would be therefore stric-tly connected with the reducing properties o~ the drug.
It has been also stated that the Ca/Phosphate ratio in the lens and its pathological fluctuations can play an important role in he formation of the cataract (V.K. Srivastava et al., Amn. Ophtalmol., 1989, 21 (4~ 9-152).
The action of calcitonin on calcium levels has been studisd in vitro in the sheep lens, finding out that calcitonin raises the calcium levels propor-tionally with the incubation times, according to a not yet explained mechanism. I(V.K. Srivastava et al. Curr. Sci. 1988, 57 (5), 295-296).

The same authors showed that th~ parenteral admini-stration of vitamin D2 and pig calcitonin to rats causes hypercalcemia and hypocalcemia in the lens and in the plasma respe~tively.
Accordingly they have suggested the possibility to regulate the calcium levels with effective doses of vitamin D~ and calcitonin, said levels being criti-cal ~or the formation of the cataract. (V.K. Sriva-stava et al., Indian J. Exp. Biol. 1987, 25 (5~, 6 ~"~

345-346).
So far a pharmacotherapy resolutive of the pre-se-nile and senile idiopathic cataract does not exist and its ~inal solution remains the surgical opera-tion.
Awaiting this last step, symptomatic drugs having prevailingly an anti-inflammatory action are some-times used, said drugs should have the property to slower the maturation of the cataract and the wor-sening of the visual acuity.
It is well known that the effectiveness level of these drugs is moderate. Thus, pharmacotherapy of cataract remains an unsolved problem.
In JP 61-17~.928 there is provided the parenteral, rectal, intradermial or oral administration of na-tural calcitonins or aminosuberic analogues thereof as visual acuity regulators.
Calcitonin is a simple polipeptidic hormone made up of 32 amino acids. The aminoacid sequence and their pattern in the calcitonin of the different animal species differ in a more or less remarkable way, although the physiological functions of said hormone remain substantially unchanged.
It seems that said functions regard the lowering of calcium ion and of inorganic phosphorus in blood, 7 ~ 3.~

through an action on bones, on the intestinal appa-ratus, on kidneys, etc... Calcitonin is used in the treatment of the Paget disease, in osteoporoses, in hypercalcemiae and generally in all the diseases connected to an excess of calcium in blood, the diseases for which calcitonin is usually admi-nistered through parenteral or nasal way.
The ocular way could in theory be employed ~or the systemic administration of this polipeptide but it is not actually employed because of its low absorp-tion due to the washing effect of the tears, to the enzymatic barriers and to the binding to the proteins of the tears and the ones of the corneal area; experimental data on the calcitonins absorp-tion through ocular absorption are therefore not known (Lee et al., Int. J. Pharm. 1986, 29, 43-51;Lee et al., Pharm. Technol. 1987, 26-38).
In the present invention the term ~Icalcitonin~ me-ans a calcitonin of natural origin such as the sal-mon, pig, eel or human one, and the semi- or total synthetic derivatives too with a similar structure and pharmacological activity; all these products are available on the market and widely described in scientific literature.
It has been now surprisingly found that using cal-citonin topically an evident slowdown of the cata-ract maturation and a visual capacity relative sta-bilization without remarkable systemic effects can be obtained; retarding in this way the cataract re-solution by surgical operation.
The object of the present invention is therefore the use of calcitonin, as active principle, in the preparations of medicaments for the therapeutic to-pical application of the presenile and senile idio-pathic cataract.
The pharmaceutical compositions usable for the above described purpose, contain calcitonin as the active principle, in a dosage unit of 0.05 U.I. to 20 U.I.. The term "International unit" (U.I.) as used in the present invention corresponds to the definition established by the WHo in relation to the International Reference Preparations for the different calcitonins species (the human, pig, sal-mon and eel ones) biological assay distributed by the National Institute for Biological Standards and Control (NIB-SAC), South Miims, Potters bar, Hert-fordshire, EN6 3OG, United Kingdom.
Said pharmaceutical compositions contain calcito-nin, as the active principle, and a pharmaceuti-cally acceptable carrier useful ~or the preparation of a medicament for the topical application.
The pharmaceutical compositions for ocular admini-stration of the presenk invention i5 carried out by suitable pharmaceutical forms such as, for in-stance, collyriums and ocular baths. The active principle used for the preparation of the collyrium must have a proper purity and the carrier consists of for instance, deionized, non-pyrogenic and ste-rile water.
Buffer mixture such as, for instance, citrates and phosphates, isotonic agents such as, for instance, sodium chloride; antioxidants such as, for in-stance, methyl or propyl p-hydroxy benzoate; wet-ting agents such as, for instance, qua ernary ammo-nium salts and pentacyclic triterpenes can be added in the carriers; and agents modulating the penetra-tion of the lenticular barrier if necessary.
In the preparation of the collyrium for the use de-scribed in the present invention, it is preferred in particular to use elcatonin in a dosage unit of ~rom 0.05 to 20 U.I. which will be contained in a volume of 5-lS ml of a carrier consisting of deionized, a pyrogenic and sterile H20, with the addition of a buffer of citric acid and sodium citrate, preferably obtained by total - synthetic 2~ ~ r~
way, to obtain a pH from 5.0 to 7.0; surfactants such as ammonium, sodium or potassium glycyrrhizinate and benzalconium chloride;
preserving agents such as methyl or propyl p-hydroxy benæoate; and modulators of the penetration of the lenticular barrier in a concentration from 0.1% to 0.5% (pv~ of the total volume of the formulation. If desired, an impromptu collyrium can also be prepared, consisting of a pharmaceutically suitable carrier contained in a sealed ampoule and of an active principle, contained in a separate container in the form of a powder or of a small sterile tablet in such a way that calcitonin, as the active principle of said compositon, is stable in time.
The above mentioned carrier cou:Ld be made of deio-nized non-pyrogenic, sterile water with the addi-tion of a buffer mixture of citric acid and sodium citrate, preferably obtained by totally synthetic way, to obtain a pH from 5.0 to 7.0; surfactants such as ammonium, sodium or potassium glycyrrhizi-nate and benzalconium chloride; preserving agents such as methyl or propyl p-hydroxy benzoate; and modulators of the penetration of thQ lenticular barrier in a concentration from 0.1% to 0.5% (pv) of the total volume of the formulation.
The pharmaceutical compositions described in the present invention, have the property to pass through the eye lenticular barrier and provide an effective therapeutical action in the presenile or senile idiopathic cataracts. Their activity has been evaluated through the pharmacological assay described hereinafter.
BIOAVAILABILITY OF THE COLLYRIUM IN THE AOUEOUS HU-MOR AND IN THE SERUM
The intraocular absorption of the collyrium prepa-red as described hereinafter in Example 1, and to-pically administered to rabbits with whole corneas has been evaluated.
42 male rabbits of the New Zealand race having a weight of about 3 kg have been used.
After instillation of fluorescein at 2% and subse-quent washing with physiological solution, the cor-neas of all the rabbits have been carefully exami-ned before of the pharmacological treatment, with the aim to realize if there are alterations in the orneal epithelium that could have influenced the trans-corneal passage of the drug.
The collyrium is employed in a percent concentra-tion of 5000 U.MRC.

~ ` ~

The animals have been divided into two groups: C.1 ml of collyrium corresponding ko 5 U~MRC have been instilled in the right eye conjunctival sac of each rabbit of the first group, while 0.1 ml of placebo collyrium (only excipients) have been instilled in the right eye conjuctival sac of each rabbit of the second group.
The lower and the upper eyelids have been gently closed after the instillation of the collyrium in order to uniformly distribute the drug.
Upon washing of the cornea and of the conjunctive with physiological solution, in order to avoid in-fections of the sample, 0.2 ml of the aqueous humor of the anterior chamber were taken by Keratocente-Si5 after surface anesthesia of the eyeball with 3%
carbocain.
At the same time a blood sample from the ear margi-nal vein has been taken for the assay of the drug in serum.
The RIA method has been utilized for the elcatonin assay in serum and in agueous humor.
The data obtained have been analyzed with the Stu-dent's t-test in order to verify the reliability of the comparison between the treatment and the placebo. -13 ~ 3~

The concentrations of elcatonin in the aqueous hu-mor of the treated rabbits appear to be high with scarce dispersion. The intraosular absorption of the drug is rapid, said drug being already present at high levels 1 hour after admninistration.
The plasma concentrations are by far lower, but they show the same tendency with a peak after the second hour.
No animal showed systemic phenomena of the drug intolerance nor local toxic phenomena, concerning in particular the corneal epithelium.
After the Keratocentesis a new test of the corneal surface integrity was performed with instillation of 2% fluorescein and washing with physiological solution.
It can be concluded that the topical administration of elcatonin is more suitable than the systemic one, because it allows to reach therapeutically ef-fective concentrations in the aqueous humor and it does not involve systemic intolerance risks.

1600 ~g of elcatonin (6500 U.I./mg activity) have been exactly weighed and dissolved at room tempera-ture under a sterile nitrogen stream and stirring, in a carrier composed by 37 mg of cit.ric acid and 14 2~ ~J'~

63 mg of sodium dihydric citrate as bufferinq agents; 130 mg of methyl p-hydroxy benzoate and 20 mg of propyl p-hydroxy benzoate, as preserving agents; and H2O to 100 ml.
The pH is adjusted to 6.0 with NaOH lN.

The composition is prepared as provided in the Example 1, using 200 mg of acetic acid and 200 mg sodium trihydrate acetate (total synthetic quality) as buffering agents, the pH is fixed at 5.0 adding HCl lN.

Claims (4)

1. Use of calcitonin as the active principle, in the preparation of medicaments for the therapeu-tical topical application in the presenile and se-nile idiopathic cataract.

2. Use according to claim 1 of calcitonin in a dosage unit from 0.05 I.U to 20 I.U..

3. Use according to claims 1 and 2 of a phar-maceutical composition containing calcitonin as the active principle and a pharmaceutically suitable carrier useful for the preparation of a medicament for the therapeutical application in cataract.

4. Pharmaceutical composition for use accor-ding to claims 1 to 3, wherein said composition contains elcatonin as the active principle and a pharmaceutically suitable carrier for the prepara-tion of the collyrium as pharmaceutical form.