N-acetylcysteine (NAC) is a compound known for time and mainly used in therapy as mucolytic and expectorant (The Merck Index, XII ed., page 16, no. 89).

Usually NAC is administered by topical route or by oral route in the form of a granulate or tablet.

For the oral solid administration, presently NAC is formulated only at the maximum dose of 200 mg in chewable tablets to be dissolved in the mouth. This implies the need to mask the taste as well as the smell of this active ingredient, known to be not very pleasant because of the presence of a sulphur group in the molecule.

Just for the need to use a high number and amount of excipients to mask the taste and the smell, there are on the market neither oral NAC formulations containing more than 65% by weight of active ingredient nor NAC formulations as swallowable tablets with a dose higher than 200 mg/tablet.

The formulation of tablets for the oral administration containing a high percentage of active ingredient is generally difficult.

US patent 4,908,210 (Eastman Kodak Company) claims a compressible powder containing 0.5-5% by weight of a specific mixture of lubricants (monoglycerides, propylene-glycol monoesters, a salt of a fatty acid ester of lactic acid) so to give finished tablets containing a percentage of active ingredient higher than 80%. Such a powder shows economic drawbacks since some excipients of the lubricant mixture are particularly expensive.

US patent 5,501,861 (Takeda Chemical Industry Ltd) illustrates fast dissolving tablets containing the active ingredient in the percentage of 0.05-90% by weight of the semifinished product and a hydrosoluble carbohydrate in a percentage of 30-80% by weight. However. this document underlines that the use of 30-70% by weight of active ingredient is preferred to obtain a tablet with a high dosage. In fact, the examples of final formulation never contain percentages of active ingredient higher than 50%.

US patent 5,401,514 (Spirig AG) claims an oral solid formulation of at least 50% NAC or carboxy-methyl-cysteine by weight in admixture with at least a cellulose, a soluble sugar. a

sweetener and a flavour. The same formulation is claimed with a NAC content of 100 mg and 200 mg. The content of active ingredient in the exemplified formulations reaches 65% by weight at the maximum.

A swallowable tablet with a high content of NAC has been now found.

Therefore, the present invention relates to a swallowable tablet containing 80-95% NAC by weight, 0.5-4% by weight with respect to NAC of a binder and further pharmaceutically acceptable excipients.

Preferably, the swallowable tablet object of the present invention contains 80-95% NAC by weight, 1-3% binder by weight, 2.5-14% diluent by weight, 1-4.5% disintegrant by weight, 0.1-1.5% lubricant by weight, optionally in the presence of a flowing agent and of a film- coating layer.

Still more preferably, the swallowable tablet object of the present invention contains 80-90% NAC by weight, 2-3% binder by weight, 3-14% diluent by weight, 1-4.5% disintegrant by weight, 0.1-1% lubricant by weight, 0.1-1% flowing agent and optionally a film-coating layer equal to or lower than 4% by weight.

Examples of binders according to the present invention are linear polyvinylpyrrolidone, sodium carboxymethylcellulose, ethylcellulose, methylcellulose, liquid glucose, gelatine and hydroxypropylcellulose.

Preferably linear polyvinylpirrolidone is used.

Examples of lubricants according to the present invention are magnesium stearate. sodium stearyl fumarate, sodium benzoate and polyethvlene glycol.

Magnesium stearate is preferably used.

Examples of diluents according to the present invention are carbohydrates, such as lactose and saccharose, microcrystalline cellulose and derivatives thereof, inorganic salts. such as dibasic calcium phosphate and sodium bicarbonate, polyalcohols, such as sorbitol, mannitol and xylitol, and mixtures thereof.

Microcrvstalline cellulose and its derivatives or mixtures thereof are preferably used.

Examples of disintegrants according to the present invention are cross-linked polyvinylpyrrolidone, sodium croscarmellose. sodium carboxymethyl starch, starch,

pregelatinized starch and microcrystalline cellulose.

Cross-linked polyvinylpyrrolidone and sodium croscarmellose are preferably used.

When present, the preferably used flowing agent is colloidal silica.

The tablet object of the invention is prepared by wet granulation of the active ingredient with a binder and optionally all or part of the estimated amount of diluent and/or of the lubricant.

The granulate is then mixed and compressed with the other excipients and the resultant tablet optionally undergoes a film-coating procedure.

This optional film-coating is carried out according to conventional techniques by preferably using cellulose acetate phthalate. ethvlcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and metacrylic acid co-polymers, as coating agents, in admixture with opacifiers, plasticizers and, optionally. dyes and sweetening agents.

Preferably the preparation of the swallowable tablet object of the present invention is carried out by wet granulation of NAC with a binder. The resultant granulate is then mixed with the remaining excipients and compressed.

The use of such a low amount of excipients makes possible the preparation of swallowable tablets containing a high dose of NAC, while keeping the final size of the tablet within acceptable values, that is suitable for the swallowing.

A particularly preferred feature of the present invention is therefore represented by the preparation of tablets containing a dose of NAC equal to or higher than 400 mg, more preferably equal to 600 mg.

The tablets containing 600 mg NAC, according to the present invention, have a weight from 630 mg to 750 mg. For the preparation of tablets having this weight, conventional moulds such as, for example, convex tablets with 12-mm diameter or capsule-shaped tablets with sizes 18.16 x 7.41 mm, commonly used for swallowable tablets, can be used.

Furthermore, the tablets object of the present invention show physical characteristics which fulfil the requirements imposed by the Official Pharmacopoeias.

For example, the hardness of the tablets will be generally from 6 to 14 Kp. the friabilitv from 0.05 to 0.7% and the disintegration time lower than 15 minutes for the non-film coated tablets.

In order to better illustrate the present invention the following examples are now given.

Example 1 Preparation of the granulates By using a wet granulation procedure in a rotogranulator, the following granulates were prepared (% by weight): GRANULATE A B C D E F G H NAC 97% 98% 89% 90% 89% 90% 96% 89% PVP K30 3% 2% 3% 2% 3% 2% 3% 2% ----8%8%------------8%lactose---- ------------8%8%--------mannitol---- ------------------------1%1%PEG6000 The granulats (2 Kg each batch) were dried, screened and used for the preparation of the tablets according to what reported in the following examples.

Example 2 Granulate A (2 Kg) was mixed with microcrystalline cellulose, sodium bicarbonate, PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (84.4%) PVP K30 18.0 mg (2.5%) microcrystalline cellulose 50.8 mg (7.1%) sodium bicarbonate 20.0 mg (2.8%) PVP CL 16.0 mg (2. 3%) magnesium stearate 6.2 mg (0.9%) total weight 711.0 mg Example 3 Granulate A (2 Kg) was mixed with microcrystalline cellulose, PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (83.8%)

PVP K30 18.0 mg (2.5%) microcrystalline cellulose 75.8 mg (10.6%) PVP CL 16.0 mg (2.2%) magnesium stearate 6.2 mg (0.9%) total weight 716.0 mg Example 4 Granulate A (2 Kg) was mixed with microcrystalline cellulose, PVP CL, magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (83.9%) PVP K30 18.0 mg (2.5%) microcrystalline cellulose 60.0 mg (8.4%) PVP CL 30.0 mg (4.2%) magnesium stearate 3.5 mg (0.5%) colloidal silica 3.5 mg (0.5%) total weight 715.0 mg Example 5 Granulate A (2 Kg) was mixed with dibasic calcium phosphate, PVP CL. magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (83.8%) PVP K30 18.0 mg (2.5%) dibasic calcium phosphate 60.8 mg (8.5%) PVP CL 30.0 mg (4.2%) magnesium stearate 3.6 mg (0.5%) colloidal silica 3.6 mg (0.5%) total weight 716.0 mg Example 6 Granulate A (2 Kg) was mixed with lactose. PVP CL. magnesium stearate and colloidal

silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (83.33%) PVP K30 18.0 mg (2.50%) lactose 75.0 mg (10.42%) PVP CL 16.0 mg (2.22%) magnesium stearate 6.4 mg (0.89%) colloidal silica 4.6 mg (0.64%) total weight 720.0 mg Example 7 Granulate A (2 Kg) was mixed with microcrystalline cellulose, sodium croscarmellose and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (85.7%) PVP K30 18.0 mg (2.6%) microcrystalline cellulose 45.8 mg (6.5%) sodium croscarmellose 30.0 mg (4.3%) magnesium stearate 6.2 mg (0.9%) total weight 700.0 mg Example 8 Granulate A (2 Kg) was mixed with microcrystalline cellulose, PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (85.7%) PVP K30 18.0 mg (2.6%) microcrystalline cellulose 45.8 mg (6.5%) PVP CL 30.0 mg (4.3%) magnesium stearate 6.2 mg (0.9%) total weight 700.0 mg

Example 9 Granulate C (2 Kg) was mixed with PVP CL. magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight).

NAC 600.0 mg (84.4%) PVP K30 20.0 mg (2.8%) lactose 54.0 mg (7.6%) PVP CL 30.0 mg (4.2%) magnesium stearate 4.0 mg (0.6%) colloidal silica 3.0 mg (0.4%) total weight 711.0 mg Example 10 Granulate D (2 Kg) was mixed with microcrystalline cellulose, PVP CL, magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (82.6%) PVP K30 15. 0 mg (2.1%) lactose 54.0 mg (7.4%) microcrystalline cellulose 30.0 mg (4.1%) PVP CL 20.0 mg (2.8%) magnesium stearate 4.0 mg (0.6%) colloidal silica 3.0 mg (0.4%) total weight 726.0 mg Example 11 Granulate E (2 Kg) was mixed with microcrystalline cellulose. PVP CL, magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (81.52%) PVP K30 20.0 mg (2.72%)

mannitol 54.0 mg (7.34%) microcrystalline cellulose 30.0 mg (4.08%) PVP CL 25.0 mg (3.40%) magnesium stearate 4.0 mg (0.54%) colloidal silica 3.0 mg (0.40%) total weight 736.0 mg Example 12 Granulate F (2 Kg) was mixed with dibasic calcium phosphate, PVP CL, magnesium stearate and colloidal silica. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% bv weight): NAC 600.0 mg (81.52%) PVP K30 15.0 mg (2.04%) mannitol 54.0 mg (7.34%) dibasic calcium phosphate 40.0 mg (5.44%) PVP CL 20.0 mg (2.72%) magnesium stearate 4.0 mg (0.54%) colloidal silica 3.0 mg (0.40%) total weight 736.0 mg Example 13 Granulate G (2 Kg) was mixed with microcrystalline cellulose, sodium bicarbonate, PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (84.39%) PVP K30 18.0 mg (2.53%) PEG 6000 6.0 mg (0.84%) microcrystalline cellulose 50. 8 mg (7.15%) sodium bicarbonate 14.0 mg (1.97%) PVP CL 16.0 mg (2.25%) magnesium stearate 6.2 mg (0.87%)

total weight 711.0 mg Example 14 Granulate G (2 Kg) was mixed with microcrystalline cellulose, colloidal silica. PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (83.22%) PVP K30 18.0 mg (2.49%) PEG 6000 6.0 mg (0.83%) PVP CL 30.0 mg (4.16%) microcrystalline cellulose 60.0 mg (8.32%) colloidal silica 3.5 mg (0.49%) magnesium stearate 3.5 mg (0.49%) total weight 721.0 mg Example 15 Granulate G (2 Kg) was mixed with microcrystalline cellulose, colloidal silica, PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% bv weight): NAC 400.0 mg (83.22%) PVP K30 12.0 mg (2.49%) PEG 6000 4.0 mg (0.83%) PVP CL 20.0 mg (4.16%) microcrystalline cellulose 40.0 mg (8.32%) colloidal silica 2.33 mg (0.49%) magnesium stearate 2. 33 mg (0.49%) total weight 480.66 mg Example 16 Granulate G (2 Kg) was mixed with microcrystalline cellulose, colloidal silica. PVP CL and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight):

NAC 200.0 mg (83.22%) PVP K30 6.0 mg (2.49%) PEG 6000 2.0 mg (0.83%) PVP CL 10. 0 mg (4.16%) microcrystalline cellulose 20.0 mg (8.32%) colloidal silica 1.16 mg (0.49%) magnesium stearate 1.16 mg (0.49%) total weight 240.32 mg Example 17 Granulate A (2 Kg) was mixed with PVP CL. microcrystalline cellulose, colloidal silica and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 400.0 mg (83.92%) PVP K30 12.0 mg (2.52%) PVP CL 20.0 mg (4.19%) microcrystalline cellulose 40.0 mg (8.39%) colloidal silica 2.33 mg (0.49%) magnesium stearate 2. 33 mg (0.49%) total weight 476.66 mg Example 18 Granulate A (2 Kg) was mixed with PVP CL, microcrystalline cellulose, colloidal silica and magnesium stearate. The mixture was compressed to obtain tablets having the following composition expressed as mg/tablet (% by weight): NAC 200.0 mg (83.92%) PVP K30 6.0 mg (2.52%) PVP CL 10.0 mg (4.19%) microcrystalline cellulose 20.0 mg (8.39%) colloidal silica 1.16 mg (0.49%) magnesium stearate 1.16 mg (0.49%)

total weight 238.32 mg Example 19 The tablets prepared as described in example 4 were coated with a mixture of hydroxypropylmethylcellulose, titanium dioxide and PEG 6000.

The mixture was suspended in water (suspension at 10-15%) and sprayed into a coating pan.

The resultant film-coated tablets have the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (82.4%) PVP K30 18.0 mg (2.5%) microcrystalline cellulose 60.0 mg (8.2%) PVP CL 30.0 mg (4.1%) magnesium stearate 3.5 mg (0.5%) colloidal silica 3.5 mg (0.5%) HPMC 5.0 mg (0.7%) titanium dioxide 5.0 mg (0.7%) PEG 6000 3.0 mg (0.4%) total weight 728.0 mg Example 20 The tablets prepared as described in example 4 were coated with a mixture of metacrylic acid copolymer, titanium dioxide and polysorbate 80.

The mixture was suspended in water (suspension at 10-15%) and sprayed into a coating ban.

The resultant film-coated tablets have the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (82.27%) PVP K30 18.0 mg (2.47%) microcrystalline cellulose 60.0 mg (8.23%) PVP CL 30.0 mg (4.11%) magnesium stearate 3.5 mg (0.48%) colloidal silica 3.5 mg (0.48%)

metacrylic acid copolymer 9.2 mg (1.26%) titanium dioxide 3.3 mg (0.45%) polysorbate 80 1.8 mg (0.25%) total weight 729.3 mg Example 21 The tablets prepared as described in example 4 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets (12 mm diameter) have the following composition expressed as mg/tablet (% by weight) : NAC 600.0 mg (80.7%) PVP K30 18.0 mg (2.42%) PVP CL 30.0 mg (4.03%) microcrystalline cellulose 60.0 mg (8.06%) colloidal silica 3.5 mg (0.47%) magnesium stearate 3.5 mg (0.47%) Opadry OY-B-28920 28.6 mg (3.85%) total weight 743.6 mg Example 22 The tablets prepared as described in example 14 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets (12 mm diameter) have the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (80.0%) PVP K30 18.0 mg (2.4%) PEG 6000 6.0 mg (0.8%)

PVP CL 30.0 mg (4.0%) microcrystalline cellulose 60.0 mg (8.0%) colloidal silica 3.5 mg (0.47%) magnesium stearate 3.5 mg (0.47%) Opadry OY-B-28920 28.84 mg (3.86%) total weight 749.84 mg Example 23 The tablets prepared as described in example 15 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets (10 mm diameter) have the following composition expressed as mg/tablet (% by weight): NAC 400.0 mg (80.0%) VVP K30 mg (2.4%) PEG 6000 4.0 mg (0.8%) PVP CL 20.0 mg (4.0%) microcrystalline cellulose 40.0 mg (8.0%) colloidal silica 2. 33 mg (0.47%) magnesium stearate 2.33 mg (0.47%) Opadry OY-B-28920 19.24 mg (3.86%) total weight 499.9 mg Example 24 The tablets prepared as described in example 16 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets (8 mm diameter) have the following composition expressed as mg/tablet (% by weight):

NAC 200.0 mg (80.0%) PVP K30 6.0 mg (2.4%) PEG 6000 2.0 mg (0.8%) PVP CL 10.0 mg (4.0%) microcrystalline cellulose 20.0 mg (8.0%) colloidal silica 1.16 mg (0.47%) magnesium stearate 1.16 mg (0.47%) Opadry OY-B-28920 9.58 mg (3.86%) total weight 249.9 mg Example 25 The tablets prepared as described in example 17 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets (10 mm diameter) have the following composition expressed as mg/tablet (% by weight): NAC 400.0 mg (80.7%) PVP K30 12.0 mg (2.42%) PVP CL 20.0 mg (4.03%) microcrystalline cellulose 40.0 mg (8.06%) colloidal silica 2.33 mg (0.47%) magnesium stearate 2.33 mg (0.47%) Opadry OY-B-28920 19.04 mg (3.85%) total weight 495.7 mg Example 26 The tablets prepared as described in example 18 were coated with a mixture of polyvinylalcohol. titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920.

The mixture was suspended in water and sprayed into a coating pan. The resultant film-

coated tablets (8 mm diameter) have the following composition expressed as mg/tablet (% by weight): NAC 200.0 mg (80.7%) PVP K30 6.0 mg (2.42%) PVP CL 10.0 mg (4.03%) microcrystalline cellulose 20.0 mg (8.06%) colloidal silica 1.16 mg (0.47%) magnesium stearate 1.16 mg (0.47%) Opadry OY-B-28920 9.53 mg (3.85%) total weight 247.85 mg Example 27 The tablets prepared as described in example 4 were coated with a mixture of polyvinylalcohol, titanium dioxide, talc, soya lecithin and xanthan gum, commercially available as Opadry OY-B-28920, added with sodium saccharin.

The mixture was suspended in water and sprayed into a coating pan. The resultant film- coated tablets have the following composition expressed as mg/tablet (% by weight): NAC 600.0 mg (80.6%) PVP K30 18.0 mg (2.4%) PVP CL 30.0 mg (4.0%) microcrystalline cellulose 60.0 mg (8.0%) colloidal silica 3.5 mg (0.5%) magnesium stearate 3.5 mg (0.5%) Opadry OY-B-28920 28.6 mg (3.8%) sodium saccharin 1.4 mg (0.2%) total weight 745 mg By working in a similar way, tablets having a lower content of sodium saccharin in the film- coating mixture, 1.0 mg and 0.5 mg respectively. were prepared.