FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2010 COMPLETE SPECIFICATION
(See section 10; rule 13)
"PHARMACEUTICAL COMPOSITIONS OF POORLY SOLUBLE DRUGS"
CADILA PHARMACEUTICALS LIMITED
"Cadila Corporate Campus", Sarkhej - Dholka Road, Bhat, Ahmedabad - 382210, Gujarat, India
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention is related to stable pharmaceutical compositions of Tacrolimus or its pharmaceutically acceptable salts or its derivatives having improved bioavailability and process for preparing the same.
BACKGROUND OF THE INVENTION
About 40% of drug candidates fail to advance through the clinical drug development process due to poor solubility, poor permeability or both which lead to poor bioavailability. Commonly reported strategies in literature are employed including the use of surfactants, lipids, permeation enhancers, micronization, salt formation, cyclodextrins, nanoparticles and solid dispersions to overcome poor water solubility and bioavailability.
The conventional emulsions are based on the increased solubility of therapeutic agents in oil. An approach is to solubilize a therapeutic agent in vegetable oil, and disperse the oil phase in an aqueous medium. The dispersion may be stabilized by emulsifying agents. Although conventional oil-based pharmaceutical compositions are useful in solubilizing and delivering some therapeutic agents, such compositions are often associated with limitations such as agglomeration of oil globules that may lead to phase separation with time.
Another approach is based on formation of "microemulsion" which is a dispersion of oil in water, stabilized by high amount of surfactant(s). These high concentrations of hydrophilic surfactant and solvents raise safety concern of resulting composition.
Yet another approach to improve solubility and subsequent bioavailability of poorly soluble drug include self emulsifying drug delivery system (SEDDS) comprising of oils, surfactant, co-surfactant/co-solvent and drug. The usual surfactant concentration in SMEDDS ranges between 30-60% w/w of the formulation that may raise safety concern.
Chen et a), in US patent no. 6,267,985 discloses oil-containing pharmaceutical compositions comprise of carrier, a triglyceride and therapeutic agent. The carrier is formed from a combination of at least two surfactants of which one is hydrophilic. Examples disclosed in US 6,267,985 indicated that these formulations contains high amount of surfactant (more than 50% of composition) that may have safety concerns.

Chen et al. in US patent no. 6,923,988 discloses pharmaceutical compositions in the form of a solid carrier including a substrate and an encapsulation coat on the substrate. The encapsulation coat includes combinations of pharmaceutical active ingredients, hydrophilic surfactant, lipophilic surfactants and triglycerides.
The given prior art uses more than 50% surfactant which is high amount in such poorly water and/or oil soluble drug formulations. The effect of surfactant on intestinal membrane is complex (Bermejo, D. M. and Ruiz-Garcia, A., Business Briefing: Pharmatech 2003; pages 1-7). Permeability enhancement and local damages are the major consequences of the interaction of surfactants with the intestinal wall (Swenson, E.S., Milisen, W.B., Curatolo, W., Pharm. Res. 1994 Aug; 11(8), pages 1132-42). Hence the use of high amount of surfactants in the poorly water and/or oil soluble drug formulation should be avoided.
Drugs which are poorly water and/or oil soluble include Tacrolimus, Everolimus, Pimecrolimus, Sirolimus, Temsirolimus, Paclitaxel, Nelfinavir, Raloxifene, Ritonavir, Saquinavir, Lopinavir, Cyclosporine, Itraconazole, Tamoxifen, Terbinafine, Indinavir, Tipranavir.
Thus, there is a need for pharmaceutical compositions that overcome the limitations and safety concerns of conventional formulations disclosed in prior arts.
SUMMARY OF THE INVENTION
The main object of the invention is to provide oral pharmaceutical compositions with improved bioavailability of Tacroliums.
Another object of the invention is to provide pharmaceutical composition wherein concentration of surfactant is not more than 40%.
Another object of the invention is to provide pharmaceutical composition with improved stability of formulation.
BRIEF DESCRPTION OF DRAWINGS
Figure 1 discloses the pharmacokinetic evaluation of various pharmaceutical compositions of Tacrolimus as per present invention and their comparison with commercial preparation and active pharmaceutical ingredient.

DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a stable oral pharmaceutical composition comprising therapeutically effective amount of Tacrolimus or its pharmaceutical acceptable salts or derivatives, surfactants, alcohol and antioxident, wherein surfactant concentration is not more than 40% in composition.
Present invention also relates to the pharmaceutical compositions with improved bioavailability of Tacrolimus.
The alcohol used in the present invention is selected from glycofurol, polyethylene glycol, polypropylene glycol, propylene glycol, glycerin, benzyl alcohol, and ethyl alcohol or mixtures thereof. The concentration of alcohol present in the pharmaceutical composition is in the range of 0.5 to 10%..
Oil is selected from (1) oils containing fatty acid triglycerides, preferably medium chain fatty acid triglycerides, such as fractionated coconut oil (Miglyol®, Huls; and Captex®, Abitec), caprylic/capric triglyceride (Crodamo! GTCC®), (2) oils containing mono-, di- or mono/di-glycerides, preferably mono-or di-glycerides of oleic acid, (3) oils containing esters of fatty acids and monovalent alkanols, such as isopropyl myristate, isopropyl palmitate, ethyl linoleate and ethyl oleate, (4) oils containing propylene glycol mono- or di-fatty acid esters such as propylene glycol dicaprylate, propylene glycol monocaprylate, propylene glycol dilaurate, propylene glycol isostearate, propylene glycol monolaurate and propylene glycol ricinolate. The oil present in the pharmaceutical composition is in the range of 5 to 50%.
Physiologically acceptable surfactants are generally known in the art and include various wetting agents and phospholipids. It is preferred that the physiologically acceptable surfactant which is selected from the group consisting of polysorbate, polyoxyethylene derivatives, vitamin E- TPGS, polyoxyethylene-polyoxypropylene block copolymer, cremophor. The concentration of surfactant in the pharmaceutical composition is in the range of 2 to 40%.
The antioxidant used to stabilize pharmaceutical composition of present invention comprises one or more antioxidants known in art include a substituted phenolic compounds such as butylated hydroxyanisole, propyl gallate, butylated hydroxytoluene (BHT), alpha-tocopherol and biflavonoids, carotenes, ubiquinol; organic carboxylic acid derivative such as citric acid, tartaric acid, fumaric acid, maleic acid, ascorbic acid, sodium EDTA, ascorbyl palmitate; and antioxidant

from inorganic origin such as sodium sulfite, sodium metabisulfite. The concentration of antioxidant is used in the range of 0 to 5%.
Oral formulations of present invention are prepared by mixing oil and surfactant or aqueous solution of surfactant to a solution made by dissolving active ingredient into alcohol. An antioxidant is optionally added to improve the stability of pharmaceutical compositions.
It will be understood by those of skilled in the art that numerous modifications results without departing from the spirit and scope of the present invention of stable pharmaceutical compositions of Tacrolimus or its pharmaceutically acceptable salts or derivatives having improved bioavailability. Therefore, it should be clearly understood that the following examples are illustrative only and should not be construed to limit the scope of the present invention.

Example 1: An oral pharmaceutical composition was prepared as follows:
Table 1: Quantitative composition Example 1:

Ingredients Qty/20g
Tacrolimus 0.02 g
Ethanol 2.00 g
Caprylic / capric triglycerides 8.00 g
Pluronic F68® (polyoxyethylene -polyoxypropylene block copolymer) 1.00 g
Water 8.80 g
Tacrolimus was dissolved in ethanol. The alcoholic solution of drug was added to caprylic / capric triglycerides. Pluronic F68® (Polyoxyethylene - polyoxypropylene block copolymer) was dissolved in water under stirring to achieve clear solution. Pluronic F68® solution was added to the mixture of drug solution in ethanol and caprylic / capric triglycerides and mixed to get a coarse emulsion. The resulting emulsion was further subjected to sonication for 30 minutes using probe sonicater which resulted in formation of nanoemulsion.
Example 2: An oral pharmaceutical composition was prepared as follows:
Table 2: Quantitative composition Example 2:

Ingredients Qty / 30 g
Tacrolimus 0.03 g
Ethanol 2.90 g
Caprylic / capric triglycerides 12.50 g
Vitamin E TPGS
(vitamin E d-alpha tocopheryl
polyethylene glycol succinate) 0.28 g
Polysorbate 80 138 g
Water 13.80 g
Tacrolimus was dissolved in ethanol. The alcoholic solution of tacrolimus was mixed with caprylic / capric triglycerides. Vitamin E TPGS and polysorbate 80 were dissolved in water to get a clear surfactant solution. The surfactant solution was added to tacrolimus solution in caprylic / capric triglycerides to get a coarse emulsion. The resulting coarse emulsion was

subjected to sonication for 30 minutes using probe sonicater which resulted in the formation of nanoemulsion.
Example 3: An oral pharmaceutical composition was prepared as follows:
Table 3: Quantitative composition Example 3

Ingredients Qty / 30g
Tacrolimus 0.03 g
Ethanol 3.00 g
Vitamin E TPGS (vitamin E d-alpha tocopheryl polyethylene glycol succinate) 6.00 g
PEG 40 hydrogenated castor oil 3.00 g
Propylene glycol 3.00 g
Caprylic / capric triglycerides 15.00 g
Tacrolimus was dissolved in ethanol. Vitamin E TPGS and PEG 40 hydrogenated castor oil propylene glycol and caprylic / capric triglycerides were mixed together with continuous stirring to get the liquid blend. The alcoholic solution of tacrolimus was mixed with the liquid blend with continuous stirring which results in transparent liquid formulation.
All the formulations from examples 1 to 3 were subjected to bioavailability studies in rats (n=6 per group) and showed significant improvement in bioavailability as compared to control and marketed formulation (Figure 1). Example 1 shows approx. 1.5 and 2.0 fold higher Cmax than control (API alone) and marketed formulation, respectively. Example 2 and 3 show approx. 2.4 and 3.14 fold higher Cmax than control and marketed formulation, respectively.
Example 4: An oral pharmaceutical composition was prepared as follows:
Table 4: Quantitative composition Example 4

Ingredients Qty (mg)
Tacrolimus 1.0
Ethanol 4.9
Vitamin E TPGS (vitamin E d-alpha tocopheryl 9.8

polyethylene glycol succinate)
PEG 40 hydrogenated castor oil 7.5
Propylene glycol 6.3
Caprylic / capric triglycerides 24.5
Tacrolimus was dissolved in ethanol. Vitamin E TPGS and PEG 40 hydrogenated castor oil propylene glycol and caprylic / capric triglycerides were mixed together with continuous stirring to get the liquid blend. The alcoholic solution of tacrolimus was mixed with the liquid blend with continuous stirring which results in transparent liquid formulation.
The formulations from examples 4 were subjected to bioavailability studies in rats (n=6 per group) in dose of 1 mg/ml/kg.
Table 5: Pharmacokinetic data of composition of Example 4

Parameters Example 4
AUG last 6.537
AUC inf 8.585
Cmax (ng/ml) 10.788
Tmax (Hr) 0.3
Further oral pharmaceutial composition of Example 4 was Subjected to stability study at room temperature.
Table 6: Stability data of composition of Example 4

Time % Assay
Initial 97.2
1 month 100
9 months 98.3

We claim:
1. An oral pharmaceutical composition with improved bioavailability comprises of Tacrolimus or its pharmaceutically acceptable salts or its derivatives, surfactants not more than 40%, alcohol in the range of 0.5 to 10%, oil in the range of 5 to 50% and optionally antioxidant up to 5%.
2. The pharmaceutical composition as claimed in claim 1, wherein the surfactant is selected from the group of polysorbate, polyoxyethylene derivatives, vitamin E- TPGS, polyoxyethylene-polyoxypropylene block copolymer, cremophor.
3. The composition as claimed in claim 1, wherein the alcohol is selected from the group of glycofurol, polyethylene glycol, polypropylene glycol, propylene glycol, glycerin, benzyl alcohol, and ethyl alcohol or mixtures thereof.
4. The composition as claimed in claim 1, wherein the oil is selected from the oil containing group of fatty acid triglyceride, mono-, di- or mono / di-glycerides, esters of fatty acids and monovalent alkanols, propylene glycol mono- or di-fatty acid esters.
5. The composition as claimed in claim 5, wherein the antioxidant is selected from the group of substituted phenolic compounds such as butylated hydroxyanisole, propyl gallate, butylated hydroxytoluene (BHT), alpha-tocopherol and biflavonoids, carotenes, ubiquinol; organic carboxylic acid derivative such as citric acid, tartaric acid, fumaric acid, maleic acid, ascorbic acid, sodium EDTA, ascorbyl palmitate; and antioxidant from inorganic origin such as sodium sulfite, sodium metabisulfite.
6. A process for preparing the pharmaceutical composition as claimed in claim 1 comprising the steps of
i). dissolving Tacrolimus in alcohol;
ii). Mixing oil and surfactant; and
iii). Mixing the solution of step (i) into step (ii)