WO1999047175A1

WO1999047175A1 - Pharmaceutical compositions containing melatonin inclusion complexes

Info

Publication number: WO1999047175A1
Application number: PCT/EP1999/001539
Authority: WO
Inventors: Giancarlo Santus; Roberto Golzi; Giampiero Besana
Original assignee: Recordati S.A. Chemical And Pharmaceutical Company
Priority date: 1998-03-13
Filing date: 1999-03-10
Publication date: 1999-09-23
Also published as: AU3410099A; ITMI980510A1; IT1298731B1

Abstract

Disclosed are pharmaceutical compositions containing inclusion complexes of melatonin in a polymeric material, in particular in β-cyclodextrine. These compositions are particularly useful for dissolving melatonin in aqueous solvents and increasing melatonin bioavailability.

Description

PHARMACEUTICAL COMPOSITIONS CONTAINING MELATONIN INCLUSION

COMPLEXES

Field of the invention

The present invention relates to pharmaceutical compositions containing inclusion complexes of melatonin in a polymeric material. These compositions are particularly useful for dissolving melatonin in aqueous solvents.

State of the art

Melatonin, N-acetyl-5-methoxytryptamine, is a hormone mainly secreted by the pineal gland and responsible for numerous physiological responses in humans (Arendt J., Melatonin and the mammalian pineal gland, 42-207, 1995, Chapman &

Hall Ed.).

There are several therapeutic effects for which melatonin is considered to be responsible. Among these, that of a biological rhythm synchroniser and in particular acting as a normaliser of the waking/sleeping rhythm, of an antifertility agent, of an agent slowing down ageing processes and others. An important role of melatonin seems to be that of controlling growth hormone secretion with a possible synergic action in antitumour treatments which use a combination of various drugs.

From a biochemical point of view, melatonin is known as a potent antioxidant and it has been suggested that it may protect the DNA and cell reproduction processes against errors which cause changes in the reproduction system, such as interaction with free radicals and mutagenic agents.

Melatonin is characterised by low solubility in water (5.10-3 M) (Shida C, Journal of Pineal Research, 16:198-201, 1994) and, administered orally to humans, it exhibits a low bioavailability (about 30%) which is also characterised by high variability (10 to 56%) in the same subject, due both to liver metabolism reactions and absorption variability dependent on the different administration conditions and characteristics of the subject treated (Wei-Li D., New England Journal of Medicine,

336:1028-1029, 1997). The need to improve melatonin solubility is, therefore, a felt problem; a direct attempt to solve this problem is shown in the European patent Fraschini F., EP 330625, describing the use of an adenosine/melatonin mixture (in a 4:1 ratio) in order to dissolve the melatonin. Unfortunately, the solubility values obtained in this way are not significantly higher than those of melatonin as such. Konsil J., Drug Dev. Ind. Pharm., 21:1377-1387, 1995, describes the combination of hydroxypropyl-β-cyclodextrine with propylene glycol as a carrier for melatonin in topical creams. However, here the focus was on increasing transdermal drug permeation, which is known to require a certain amount of lipophily; no suggestion is given on how to enhance melatonin dissolution. In summary until now no satisfactory solution is available to enhance melatonin solubility and bioavailability, especially when this drug has to be administered into- or via acqueous environments, as in the case of oral and buccal administration. Summary

In the frame of Applicant's research for improving the bioavailability of melatonin, it has now been found, and this is an object of the present invention, that by forming inclusion complexes of melatonin with an appropriate polymer (e.g. β-cyclodextrine) it is possible to improve the solubility and the bioavailability of melatonin, in particular when melatonin is to be delivered into an aqueous environment, like in the case of oral administration. Inclusion complexes are defined as formations made up of a polymeric material and an active ingredient, where the active ingredient is included in the polymer. The polymer helps carrying the drug in the aqueous medium changing some of the physical properties typical of the active ingredient so that, after the complex has formed, the solubility of the active ingredient in aqueous solvents increases to a particularly significant extent. General reference to inclusion complexes can be found in Kirk Orthmer, Ed. 3, 6:179, 1979, where the different methods available for their preparation, such as, for example, co-grinding, lyophilisation, spray-drying and granulation, are also described. In the present invention, the term inclusion complexes also includes those preparations where the active ingredient is supported by a polymeric material which carries it and helps its dissolution. Detailed description of the invention

The inclusion complexes which are part of the invention may include various polymeric materials such as water-soluble complexing agents, hydrophilic linear polymers or swelling reticulated polymers insoluble or slightly soluble in water. The complexes can be prepared using known preparation methods by mixing the polymer with the active ingredient in varying ratios depending on the final characteristics desired.

The materials for active-ingredient inclusion or support complexes which can be used to implement the present invention include: - water-soluble complexing agents such as, for example, α-, β-, g-cyclodextrines and their derivatives such as, for example, hydroxypropyl-β-cyclodextrine. In this class, β-Cyclodextrine is the preferred agent for melatonin inclusion. - hydrophilic linear polymers such as polyvinylpyrrolidone (PVP), cellulose and their derivatives. In this class PVP is the preferred inclusion agent for melatonin. - insoluble or slightly-soluble reticulated polymers which swell upon contact with water such as reticulated polyvinylpyrrolidone (PVP XL), reticulated cyclodextrines, reticulated carboxymethylamide, dextrans. The preferred inclusion agent in this class is PVP XL. As mentioned above, among the various inclusion complexes mentioned above β-cyclodextrines are particularly suitable for dissolving melatonin in water. Cyclodextrines are cyclic oligosaccharides where the glucopyranoside units are bound by glucoside bonds. The cyclodextrine molecules are characterised by a hydrophilic outer surface and an apolar central inner cavity. This allows slightly polar molecules to penetrate into the cyclodextrine lipophilic cavity forming an inclusion complex.

Usually, in the complex formed according to the present invention, melatonin and the vehicle are present in a 1 :1 molar ratio. However this ratio can be lower or higher depending on the peculiar characteristics of the polymer chosen and dissolution profile which melatonin should appropriately possess during administration. In practice, molar ratios ranging from 1 :0.5 to 1 :20, preferably from 1 :1 to 1 :4, are used. The methods of preparation which can be used to prepare the inclusion complexes as defined in this invention can be of different types and are anyhow part of the known art. Examples of these methods include:

- co-grinding, which is based on intimate mixing of the active ingredient and selected inclusion vehicle by grinding. Dry co-grinding can use various types of mills (with rotating or vibrating spheres, rotor or high-energy mills) or any other apparatus for grinding/micronising capable of making crystalline melatonin partially or totally amorphous. A variant of this method which uses high-energy mills to prepare the co-ground material is particularly suitable for the formulations of the present invention as it allows a melatonin complex with a very small particle size, typically smaller than 10 μm and preferably smaller than 5 μm, to be obtained. Obtaining these particles allows further optimisation of the solubility characteristics of the complex and active ingredient included.

- lyophilisation, according to which the active ingredient and polymer are dissolved in a solvent, generally water. The solution is then frozen and the solvent removed by sublimation under vacuum leaving the active ingredient included in the polymer as a residue.

- granulation, according to which melatonin is dissolved in water at 50°C and mixed with the polymer in which it is to be included. After mixing, the water is removed by drying at 45°C.

- spray-drying, according to which melatonin and the polymer are both distributed in an appropriate solvent. The suspension is sprayed in a hot-air current so that the solvent can evaporate leaving the inclusion complex as a residue.

- precipitation, according to which the complex is precipitated from a cyclodextrine and melatonin aqueous solution. The solution is hot-stirred (about 50-60°C) and the complex which forms after cooling is separated by filtration. Using the melatonin-cyclodextrine inclusion complex, it is possible to obtain pharmaceutical compositions of various types for administration e.g. by the oral, parenteral, rectal, nasal, ocular, vaginal or buccal route. These compositions, which form a further embodiment of the present invention, show an enhanced dissolution rate and a higher bioavailability of melatonin with 5

respect to conventional melatonin formulation. When they are delivered into- or via an aqueous environment, like in case of oral or buccal administration, the melatonin bioavailability especially enhanced.

These pharmaceutical compositions can be formulated into conventional pharmaceutical forms such as hard-gelatine and soft-gelatine capsules; various types of tablets including rapid-dissolution, coated, sugar-coated, slow-release, enteric-coated and lyophilised tablets; granulates; suppositories; solutions for various uses: nasal spray, drops, syrups and the like.

Excipients and preparation methods which are commonly known to an average expert in the art and described both by normal technical manuals and pharmacopoeias, are used for preparation of these pharmaceutical forms.

The pharmaceutical compositions according to the invention are generally suitable to provide a daily-dosage of the melatonin inclusion complex in a range from 0.1 to 100 mg, preferably from 1 to 10 mg. The compositions according to the present invention can be used in all those therapeutic areas where melatonin has been found to have a biological activity, such as in tumour prevention and treatment, AIDS treatment, treatment of panic conditions; it can further be used as a medicament having antispastic effects, mild hypnotic effects, myelotropic actions, antimitotic actions, modulating action of NK-cell activity, maintaining an effective immune response and controlling the circadian rhythms.

The examples given below are only intended to better describe the subject invention and demonstrate its advantages and applicability, without being a limitation of same. EXAMPLE 1

Preparation of a complex with cyclodextrines

A) By precipitation

A melatonin solution obtained by heating 1 g of melatonin in 1 litre of water to

50°C was added to a solution of 5.52 g of β-cyclodextrine in 500 ml of water so as to form a solution with a 1 :1 molar ratio. The solution obtained was stirred for 24 hours at 25°C, then cooled to 4°C. The precipitated material was collected, filtered 6

and dried under vacuum.

B) By lyophilisation

A solution obtained by mild heating of a 1 :4 molar mixture made up of 232 mg of melatonin and 5.13 g of β-cyclodextrine was filled into 10-cm-diameter plates and lyophilised in a Brizio-Basi freeze-drier using a cycle with the following experimental conditions: cooling -35°C for 4 hours, vacuum 0.1-0.2 mBar, lyophilisation time 24 hours. 5.2 g of complex were obtained.

C) By hot stirring

A solution of melatonin and β-cyclodextrine in a 1 :2 molar ratio was prepared in 1 litre of water, heated to 50°C for 1 hour, then allowed to cool with stirring and slowly evaporated under vacuum to obtain the desired complex.

D) By dry co-grinding

232 g of melatonin and 5130 g of β-cyclodextrine in a 1 :4 molar ratio were dry mixed and transferred into a high-energy mill (Sweiko, USA) for 4 hours. Grinding time can be extended or shortened depending on the degree of amorfism desired and residual cristallinity one wants to obtain. In the end the product was poured and sieved on a 5000-mesh sieve.

E) By granulation

0.742 kg of melatonin and 32.77 kg of β-cyclodextrine in a 1 :8 molar ratio were mixed in a high-speed mixer/granulator. β-Cyclodextrine was added first and then an alcoholic solution containing melatonin to a concentration of 10%. These were mixed for 25 minutes and the granulate was removed and dried under vacuum.

F) By spray-drying

5 litres of an aqueous mixture made up of 10 g of melatonin and 55.28 g of β-cyclodextrine in a 1 :1 molar ratio were heated to 50°C with stirring. The solution obtained was transferred into a NIRO-ATOMISER (UK) spray-drier and the solvent was evaporated off in the following operating conditions: feeding rate 750 ml/hour, air temperature 105°C, air flow 100 cu.mJhour.

EXAMPLE 2 The inclusion compound obtained according to any method described in Example

1 was characterised by the following analytical methods: 7

A) Differential thermal analysis (DSC)

The differential thermal analysis data were conducted using a Mettler TA 300 (DSC 20) apparatus at a rate of 10°C/minute in a nitrogen current in a temperature range of 30 to 400°C. Figure 1 shows the chromatograms of: a) pure melatonin b) pure ^β-cyclodextrine c) a physical mixture of melatonin + β-cyclodextrine (1 :1 molar ratio) d) a melatonin/β-cyclodextrine inclusion complex in a 1 :1 molar ratio for the most significant temperature range (40 to 200°C). A comparison of the chromatograms shows the disappearance in plot d) of the melatonin melting peak at about 118°C due to formation of the inclusion complex.

B) IR spectroscopy

The IR spectra were performed suspending the compounds in mineral oil using an FTIR mod.-1600 apparatus (PERKIN-ELMER). Figure 2 shows: a) a pure melatonin spectrum b) a pure β-cyclodextrine spectrum c) overlapping of the spectrum of the melatonin/ β-cyclodextrine inclusion complex in a 1 :1 ratio (d ) and spectrum of the melatonin + β-cyclodextrine physical mixture (c2).

The changes of the bands typical of melatonin in the inclusion complex, in particular the absorption bands at 1200 cm^"1 and 1600 cm^"1, are evident. EXAMPLE 3 Solubility in water Samples of pure melatonin, melatonin mixed with adenosine in a 1 :4 ratio according to the description in patent Fraschini F., EP 330625 and melatonin/β-cyclodextrine inclusion complex, prepared as described in methods B and D respectively in Example 1 , were transferred into 50 ml of distilled water at 20°C in the presence of corpo di fondo. The suspensions were stirred in a shock agitator and samples of the supernatant were taken and, after filtration on a Millipore membrane, read on a VARIAN spectrophotometer at a wavelength of 276 nm. Table 1 shows the solubility values (mol/litre) found.

TABLE 1

Solubility in distilled water at 20°C

Sample Solubility (Mol/L)

Melatonin 5.0 10^"3

Melatonin/adenosine mixture 1 :4 6.0 10^"3

Example-1 complex, method B 3.0 10^"2

Example-1 complex, method D 2.7 10^"2

These results show that the solubility of the melatonin/β-cyclodextrine complex according to the present invention is considerably higher than that of the prior art comparative formulations. EXAMPLE 4 Preparation of capsules containing the inclusion complex The melatonin/β-cyclodextrine complex prepared according to one of the methods described in Example 1 was mixed with spray-dry lactose and magnesium stearate for 12 minutes in a TURBULA mixer. In the end, the powder mixture was filled into size-3 capsules containing the equivalent of 2 mg of melatonin having the following composition: melatonin/β-cyclodextrine 15 mg, spray-dry lactose 83 mg, magnesium stearate 2 mg. EXAMPLE 5

Preparation of tablets containing the inclusion complex The melatonin/β-cyclodextrine inclusion compound in a 1 :4 ratio prepared according to the description in Example 1 (method B) was mixed in a V mixer with avicel, lactose, carboxymethylamide and magnesium stearate. 5 kg of this mixture was compressed using the direct-compression method to a weight of 200 mg/tablet in a RONCHI tabletting machine equipped with round 8-mm dies to obtain tablets having the following composition: melatonin/β-cyclodextrine 69 mg (equivalent to 3 mg of melatonin), lactose 69 mg, avicel 50 mg, carboxymethylamide 10 mg, magnesium stearate 2 mg. 9

EXAMPLE 6

Preparation of a granulate containing the inclusion complex

The melatonin/β-cyclodextrine inclusion complex in a 1 :4 ratio prepared according to the description in Example 1 (method B) was diluted with sorbitol, and lemon flavour and aspartame were then added. The mixture so obtained contained 260 mg of the melatonin/β-cyclodextrine complex equivalent to 10 mg of melatonin, and was filled into 3-gram packages each having the following composition: melatonin/ β-cyclodextrine 260 mg, sorbitol 2695 mg, lemon flavour 30 mg, aspartame 15 mg. EXAMPLE 7

Dissolution of tablets containing the inclusion complex The dissolution property of the tablets prepared according to the description in Example 5 was compared with that of tablets prepared using the same excipients but containing melatonin without β-cyclodextrine (β-CDX). Dissolution was conducted in 250 ml of 0.1 N HCI at 37°C stirring at 50 revolutions/minute, using apparatus 2 from the United States Pharmacopoeia (USP, Ed. 23, page 1791, 1995). The samples collected at the times shown in Table 2 below were analysed with a UV spectrophotometer at a wavelength of 276 nm to determine the melatonin percentage released.

10

TABLE 2

Dissolution of tablets containing melatonin

% melatonin released

Time minutes Tablets from Example 5 Tablets from Example 5 with β-CDX without β-CDX

0 0 0

10 70 15

20 91 35

30 100 45

40 100 54

50 100 60

60 100 64

These results show that melatonin dissolution from tablets containing the melatonin/ β-cyclodextrine complex is considerably more rapid than that of tablets having a similar composition but containing non-complexed melatonin.

Claims

11

1 1. A pharmaceutical composition for the administration of melatonin, comprising

2 an inclusion complex of melatonin with polymeric materials.

1 2. A composition according to claim 1 , suitable for dissolution into an aqueous

2 environment. l 3. A composition according to claim 2, suitable for oral or buccal administration.

1 4. A composition according to any of the preceding claims, characterised by the

2 fact that the polymeric materials which make up the inclusion complex are

3 selected from water-soluble complexing agents, hydrophilic linear polymers and swelling reticulated polymers insoluble in water.

1 5. A composition according to claim 4, characterised by the fact that the

2 water-soluble complexing agents are selected from α-, β-, -cyclodextrine or their

3 derivatives, and sodium carboxymethylamide.

1 6. A composition according to claim 4, characterised by the fact that the

2 hydrophilic linear polymers are chosen from polyvinylpyrrolidone (PVP), cellulose

3 and their derivatives.

1 7. A composition according to claim 4, characterised by the fact that the swelling

2 reticulated polymers insoluble in water are chosen from reticulated

3 polyvinylpyrrolidone (PVP XL), reticulated cyclodextrines, reticulated

4 carboxymethylamide and dextrans.

1 8. A composition according to any preceding claim, characterised by the fact that

2 melatonin and the polymeric materials in the inclusion complex are present in a

3 molar ratio ranging from 1 :0.5 to 1 :20, preferably from 1 :1 to 1 :4.

1 9. A composition according to any preceding claim, formulated in hard-gelatine or

2 soft-gelatine capsules; rapid-dissolution, coated, sugar-coated, slow-release,

3 enteric-coated or lyophilised tablets; granulates; suppositories; solutions: nasal

4 sprays, drops or syrups.

1 10. A process for the preparation of the inclusion complex described in any

2 preceding claim, chosen from co-grinding, lyophilisation, granulation,

3 spray-drying. l 11. A process according to claim 10, characterised by the fact that co-grinding of 12

the ingredients which make up the inclusion complex is carried out in a high-energy mill. 12. Use of the compositions according to any of claims 1-9, for the preparation of a medicament for therapeutic or preventive treatment of diseases requiring the administration of melatonin in mammals. 13. Use according to claim 12, in the treatment of tumour diseases, AIDS or circadian rhythms disorders.