TECHNICAL FIELD

The object of the present invention is a method of manufacturing a water-in-oil emulsion of nanoparticles of paracetamol.

BACKGROUND ART

Paracetamol, also known as acetaminophen or APAP, is a medication used to treat pain and fever. Paracetamol is used to treat many conditions such as headache, muscle aches, arthritis, backache, toothaches, colds, and fevers. It relieves pain in mild arthritis but has no effect on the underlying inflammation and swelling of the joint.

Patent application US20060147538A1 discloses a drug delivery composition comprising an active ingredient and a biologically inert material wherein the biologically inert material is a nanocomposite material. Preferably the biologically inert material is a polymer-clay nanocomposite comprising up to about 40% by weight of nano-sized (1- 1000 nm) clay particles dispersed in a polymeric material. The active ingredient may be dispersed in the nanocomposite material or absorbed thereto.

Patent application CN102218019A1 discloses a preparation method for a nano-granular solid dispersion of a hydrophobic drug by high- voltage electrostatic spraying, which comprises the following steps of: mixing a hydrophobic drug, a drug-carrying polymer and an organic solvent at a mass ratio of (1-10): (10-20): (80-94) to prepare a consolute electric spraying solution; and then carrying out high-voltage electrostatic spraying while controlling the flow rate of the consolute electric spraying solution at 0.5-2.5 mL h, the distance between a receiving board and a wire spraying port at 15-30cm and the voltage at 5-30kV to obtain the nano- granular solid dispersion of the hydrophobic drug. The preparation method is simple to operate, is low in cost, is environmentally-friendly and is suitable for industrial production; and the prepared solid dispersion of the hydrophobic drug not only can highly disperse a composite of a polymer and the drug into an amorphous state and has a nano- structural characteristic. Patent application WO2007053197A1 discloses a stable natioparticulate acetaminophen composition comprising:

(a) particles of acetaminophen or a salt or derivative thereof having an effective average particle size of less than about 2000 nm; and

(b) at least one surface stabilizer, castor oil derivatives.

The composition may contain castor oil or fatty acid esters of sorbitan as emulsifier.

Patent application EP2938324A1 discloses a compositions containing acetaminophen, wherein the active ingredient is stabilized and greater than 90% of the particles of the active ingredient have a particle size that is less than or equal to or any number in between 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4 nanometers, or smaller, as determined by Dynamic Light Scattering (DLS), using a volume -weighted particle size distribution calculation method.

DISCLOSURE OF THE INVENTION

The method in accordance with the present invention solves the problem of preparation of stable water-in-oil nanoemulsions of paracetamol and thus improving their bioavailability and efficacy. A method of manufacturing a water-in-oil emulsion of nanoparticles of paracetamol of the present invention consists in that, an oil phase is prepared by dissolution of paracetamol in oil, and a water phase is prepared by dissolution of at least one emulsifier/stabilizer in water, then the oil phase is added dropwise to the water phase, then the two-phase system is homogenised until an emulsion is obtained. The method allows for obtaining a stable water-in-oil nanoemulsion of paracetamol.

Preferably the oil is castor oil.

Preferably the concentration of paracetamol in oil is from 9 to 39%.

Preferably the emulsifier/stabilizer is chosen from a group consisting of lecithin, gelatine, starch and potassium sorbate. The water phase may contain one, two, three or all four emulsifiers/stabilizers.

Preferably the concentration of lecithin in water phase is from 5 to

10%.

Preferably the concentration of gelatine in water phase is from 0.5 to

2%.

Preferably, the concentration of starch in water phase is from 1 to 2%. Preferably the concentration of potassium sorbate in water phase is from 0.4 to 0.8%.

Preferably the emulsifier/stabilizer is dissolved in water in temperature not higher than do 90°C.

Preferably the mass ratio of oil phase to water phase is from 0.8: 1.0 to 1.0: 1.0.

Preferably the two-phase system is homogenised through the use of ultrasonic frequencies.

Preferably the strength of ultrasound is from 500 to 600 W.

Preferably the homogenization process is carried out from 10 to 45 minutes.

Preferably the ultrasonication is carried out in flow system or in batch system.

The present invention refers also to a water-in-oil emulsion of paracetamol nanoparticles obtained by method according to the invention. BEST MODE OF CARRYING OUT THE INVENTION

The following examples illustrate the invention without setting or delineating its limits. Example 1

A solution of paracetamol in castor oil was prepared by mixing 30 g of paracetamol with 143.6 g of castor oil. 10 g of lecithin, and 2 g of starch were dissolved in 150 g of water in temperature 80°C. Then, during continuous homogenization, the solution of paracetamol was added portion-wise to the solution of lecithin, and starch. After the whole oil- phase is added, homogenization is continued for 15 minutes. A homogeneous water-in-oil emulsion is obtained comprising paracetamol in the amount of 100 mg/cm ³ .

The Malvern Zetasizer apparatus using method of dynamic light scattering (DLS) was utilized to measure the average size of paracetamol particles. The average size of nanoparticles was 69 nm.

Example 2

A solution of paracetamol in castor oil was prepared by mixing 15 g of paracetamol with 143.6 g of castor oil. 10 g of lecithin, 2 g of gelatine, 2 g of starch, and 0.8 g of potassium sorbate were dissolved in 150 g of water in temperature 80°C. Then, during continuous homogenization, the solution of paracetamol was added portion-wise to the solution of emulsifiers/stabilizers. After the whole oil-phase is added, homogenization is continued for 20 minutes. A homogeneous water-in-oil emulsion is obtained comprising paracetamol in the amount of 50 mg/cm ³ .

The Malvern Zetasizer apparatus using method of dynamic light scattering (DLS) was utilized to measure the average size of paracetamol particles. The average size of nanoparticles was 119 nm. The size of particles was then measured after 48 hours. It was equal to 112 nm.

Example 3

A solution of paracetamol in castor oil was prepared by mixing 30 g of paracetamol with 143.6 g of castor oil. 10 g of lecithin, 1 g of gelatine, and 0.8 g of potassium sorbate were dissolved in 150 g of water in temperature 80°C. Then, during continuous homogenization, the solution of paracetamol was added portion-wise to the solution of emulsifiers/stabilizers. After the whole oil-phase is added, homogenization is continued for 15 minutes. A homogeneous water-in-oil emulsion is obtained comprising paracetamol in the amount of 100 mg/cm ³ .

The Malvern Zetasizer apparatus using method of dynamic light scattering (DLS) was utilized to measure the average size of paracetamol particles. The average size of nanoparticles was 55 nm. The size of particles was then measured after 48 hours. It was equal to 36 nm.

Potential zeta was equal to -23 mV. The absolute value of the electrokinetic (zeta) potential confirms high stability of the solution.