BR102021009918A2 - SOLID DISPERSION OF THE ANTIBIOTICS RIFAMPICIN - Google Patents

Abstract

The present invention deals with co-amorphous rifampicin (RIF) with oxalic acid (OXA). RIF is an antibiotic used in the treatment of tuberculosis and leprosy. It has low water solubility, reduced bioavailability, compromising its therapeutic efficacy, favoring adverse effects and treatment abandonment. Solid dispersions (co-amorphous) have been used to increase the water solubility of drugs. In this work, the co-amorphous RIF-OXA (1: 3) was obtained by slow evaporation of the solvent. The characterization of this material was carried out by X-Ray Powder Diffraction (XRD); Simultaneous Thermogravimetry, Derivative Thermogravimetry and Differential Thermal Analysis (TG/DTG-DTA) and Differential Scanning Calorimetry (DSC). The results of DRXP evidenced the interaction of RIF with OXA in the ratio of 1: 3 and the obtaining of the co-amorph. Its amorphous nature was confirmed by its DTA and DSC curves, as no thermal melting events were observed. The co-amorphous TG/DTG curves showed a material with good thermal stability up to 131.85 °C. Thus, the co-amorphous RIF-OXA (1: 3) is very attractive for improving the treatment of these diseases, as it favors the increase in water solubility, bioavailability and therapeutic efficacy of RIF, as well as contributing to the reduction of its Side effects.

Description

SOLID DISPERSION OF THE ANTIBIOTICS RIFAMPICIN field of invention

[001] The present invention relates to obtaining a solid dispersion of the co-amorphous type of Rifampicin (RIF), an antibiotic (bacteriostatic agent) used in polychemotherapy of tuberculosis.

Fundamentals of the invention

[002] RIF (C43H58N4O12, 822, 94 g. mol-1) is a complex molecule that has different conformations due to intermolecular interactions between its functional groups, incurring different crystalline morphologies with red-brown coloration. This drug exists in two anhydrous crystalline forms and two amorphous forms. Of the crystalline polymorphs, Form I is the stable one, while Form II is metastable. In addition to these main forms, it is found as solvates, which convert to the amorphous form after removal of the solvent. (Wicher, B., et al., Redetermination of rifampicin pentahydrate revealing a zwitterionic form of the antibiotic. Acta Crystallographica Section C: Crystal Structure Communications, 2012. 68(5): p. 209-212.).

[003] RIF is a Class II drug in the Biopharmaceutical Classification System (SCB), with low solubility in water (2.8 mg mL-1 at pH = 7.5) and high membrane permeability. This molecule presents amphoteric characteristics ("zwitterion"), as it has pKa 1.7 (related to the 4-hydroxyl group) and pKa 7.9 (related to the nitrogen of the piperazine group). Its isoelectric point being equal to 4.8 in aqueous solution. (Henwood*, S.Q., et al., Characterization of the solubility and dissolution properties of several new rifampicin polymorphs, solvates, and hydrates. Drug Development and Industrial Pharmacy, 2001. 27(10): p. 1017-1030.).

[004] Oxalic acid (OXA) or ethanedioic acid has molecular formula C2O4H2. It is available in anhydrous and dihydrate form, with molar masses of 90.03 g/mol and 120.07 g/mol, respectively. The solubility in water (20°C / 25°C) is 143 g/L, its pKa values referring to the hydrogens of its two carboxylic groups, are pKa1= 1.27 and pKa2 = 4.19, having a melting point in the anhydrous form of 189.5°C and in the dihydrate form of 101.5°C. In plants, it is usually found in combination with calcium or potassium, but it can also be formed artificially by reaction with nitric acid. PRASAD, R; SHIVAY, Y. SINGH: Oxalic acid/oxylates in plants: From self-defence to phytoremediation. Current Science, v. 112, no. 8, p. 1665-1667, 2017.

[005] Aqueous solubility is the prerequisite for absorption and obtaining a clinical response for most orally administered drugs. Poorly soluble drugs are slowly absorbed compared to those with high water solubility. It is estimated that 40% of the approved active principles and about 90% of the molecules under development have poor aqueous solubility (KAWABATA, Yohei et al. Formulation design for poorly water-soluble drugs based on biopharmaceutics classification system: basic approaches and practical applications. International Journal of Pharmaceutics, v. 420, no. 1, p. 1-10, 2011).

[006] Solid dispersions, such as co-amorphs, can be used in order to increase the water solubility of drugs. These can have numerous advantages and pharmaceutical applications, such as the homogeneous and uniform distribution of small amounts of drug in the solid state, to stabilize unstable drugs, to disperse gaseous or liquid compounds and to produce forms of prolonged drug release or else to increase the drug dissolution rates (ALMEIDA, H; AMARAL, M. H.; LOBÃO, P. Comparative study of sustained-release lipid microparticles and solid dispersions containing ibuprofen. Brazilian Journal of Pharmaceutical Sciences, v. 48, n. 3, p. 529- 536, 2012).

[007] The amorphous state is characterized by the absence of a long-range molecular order. This lack of long-range order can be attributed to a random distribution of molecular units. Individual molecules are randomly oriented toward each other and exist in a variety of conformational states. At the molecular level, these materials have properties similar to liquids, but at the macroscopic level, they have properties of solid compounds. (Newman, A., Pharmaceutical amorphous solid dispersions. 1st ed, 2015: John Wiley & Sons).

[008] The co-amorphs can be prepared with polymeric and non-polymeric materials according to the coformers used. A polymeric matrix has a high glass transition temperature (Tg) and therefore increases the Tg of the amorphous drug. Polymers act as stabilizers, decreasing molecular mobility, inhibiting nucleation and crystal growth, while drug-polymer molecular interactions inhibit amorphous recrystallization. However, there are disadvantages of polymeric co-amorphs such as low miscibility, requiring large polymer/drug ratios that lead to large dosages of the final product. Furthermore, the sensitivity to heat and humidity due to the hydroscopicity of the polymers can be a problem, since humidity reduces the Tg and can lead to phase separation and recrystallization of the starting compounds. (Karagianni, A., K. Kachrimanis, and I. Nikolakakis, Co-amorphous solid dispersions for solubility and absorption improvement of drugs: Composition, preparation, characterization and formulations for oral delivery. Pharmaceutics, 2018. 10(3): p. 98).

[009] An amorphous material has no X-Ray Diffraction peaks, typical of materials found in crystalline solids, but has a wide band. Due to the lack of long-range order, amorphous materials are more energetic than their crystalline counterparts. This gives rise to certain advantages of amorphous materials over crystalline materials, including higher specific volume, greater solubility and bioavailability, but also certain disadvantages, including risk of lower physical and chemical stability. (Newman, A., Pharmaceutical amorphous solid dispersions. 1st ed, 2015: John Wiley & Sons.)

[0010] The characterization is an essential step for the development of solid drug dispersions as well as for the development of other pharmaceutical formulations. X-Ray Diffraction (XRD) techniques can be used as structural characterization and Thermogravimetry, Derivative Thermogravimetry and Simultaneous Differential Thermal Analysis (TG/DTG-DTA) and Differential Scanning Calorimetry (DSC) for thermal characterizations (VO, Chau Le- Ngoc; PARK, Chulhun; LEE, Beom-Jin. Current trends and future perspectives of solid dispersions containing poorly waiter-soluble drugs. European Journal of Pharmaceutics and Biopharmaceutics, v. 85, n. 3, p. 799-813, 2013) .

Brief description of the drawings

[0011] Figure 1 shows a scheme of the methodology used to obtain the co-amorphous RIF-OXA (1: 3).

[0012] Figure 2 shows the X-ray diffractograms of the starting compounds (RIFREC and OXAREC), the RIF-OXA co-amorph (1: 3) and the RIF-OXAMF physical mixture (1: 3).

[0013] Figure 3 shows the thermal behavior of the co-amorphous RIF-OXA (1: 3) by Thermogravimetry, Derivative Thermogravimetry and Simultaneous Differential Thermal Analysis (TG-DTG/DTA).

[0014] Figure 4 shows the DSC curves obtained for RIFEC, co-amorphous RIF-OXA (1: 3), Physical mixture RIF-OXAMF (1: 3) and the coformer OXAREC.

Description of the invention

[0015] The materials used to obtain the co-amorphous were reagents of analytical grade from the manufacturer Sigma-Aldrich, with a degree of purity ≥ 99.0%.

[0016] Obtaining the co-amorphous RIF-OXA (1: 3) was performed using the Slow Solvent Evaporation (SLS) method. For this, 84.72 mg of RIF and 38.60 mg of OXA were weighed, obtaining a total mass of 123.32 mg, which were solubilized in 20 mL of MeOH. This solution remained in the Biothec model BT60 incubator at a temperature of 40°C±1.0°C for 4 days until the solvent had completely evaporated. After this period, the material was kept in an oven with forced air circulation, brand ETHIK TECNOLOGY, model 400-3ND, at 50°C for 2 hours, to remove solvent residue. The material obtained was collected and stored in a desiccator for further characterization. The starting compounds were recrystallized, being named as RIFEC and OXAREC, to verify the occurrence of polymorphism. A physical mixture RIF-OXAMF (1: 3) was also obtained in the same proportion of the co-amorphous to verify if the formation of the solid dispersion occurs with the methodology used.

[0017] The XRD patterns were collected at the X-Ray Diffraction Laboratory (LDRX) at the UFMA campus Bom Jesus, located in the city of Imperatriz-MA. The analyzes were performed using a PANanalytical Empyrean diffractometer, using Bragg-Brentano reflection geometry (θ-θ) and CuKa radiation (λ = 1.5418 Â), operating at a voltage of 40 kV and current of 30 mA. Measurements were performed using a PIXcel3D detector, with a step of 0.02°, time per step of 2 seconds and angular sweep (2θ) from 5° to 50°. The crystallographic peak values were obtained from the X'Pert HighScore Plus software (version 2.0). Then, the results found for the starting compounds were compared with the data reported in the crystallographic database CCDC ConQuest, version 5. 36 of the Cambridge Structural Databse System (CSD System, 2018).

[0018] The TG-DTA curves were obtained simultaneously by a thermal analyzer of the brand Shimadzu Instruments model DTG-60, equipped with a “Top plan” type scale at the Thermal Analysis Laboratory (LAT) at the UFMA Advanced campus located in the city of Imperatriz -BAD. The measurements were performed with sample masses between 2, 500 and 5, 000 mg in an α-alumina crucible and a temperature range of 25 to 900°C with a heating rate of 10°C min-1, under a nitrogen atmosphere with flow rate of 50 mL min-1.

[0019] The DSC curves of the starting compounds and the samples were obtained in a thermal analyzer at the Thermal Analysis Laboratory (LAT) at the UFMA campus Bom Jesus, performing single heating cycles within the temperature range of thermal stability of each compound, under nitrogen atmosphere and with a flow rate of 50 mL min-1 and a heating rate of 5°C min-1. The DSC equipment was previously calibrated for temperature and energy using as standard the point and enthalpy of fusion of metallic indium (Tonset= 156.4°C; ∆Hfus = 28.5 J g-1) with purity of 99.99 %. Correction factors were calculated according to the manufacturer's procedure and specification. All measurements were performed under atmospheric pressure, using sample masses of approximately 2.00 mg.

Examples of embodiments of the invention

[0020] The confirmation of the formation of the co-amorphous RIF-OXA (1: 3) was carried out by X-Ray Diffraction by powder method (DRXP), this result being represented by Figure 2. The diffractograms of the starting compounds (RIFREC and OXAREC) exhibit diffraction patterns characteristic of Form II pentahydrate and Form α-dihydrate, respectively. The diffractogram of the material in the molar ratio RIF-OXA (1: 3) showed a broad band and absence of crystallographic peaks characterizing the formation of a solid dispersion of the co-amorphous type, indicating that a drug: coformer interaction occurs, forming a new material of the co-amorphous type. In the diffractogram of the RIF-OXAMF physical mixture (1: 3), crystallographic peaks corresponding to the diffraction patterns of the starting compounds were observed, confirming that the method of slow evaporation of the solvent at 40±1°C, favors the formation of the material with -amorphous.

[0021] The thermal behavior of the co-amorphous RIF-OXA (1: 3) was analyzed by TG/DTG-DTA, whose curves are shown in Figure 3. The TG/DTG curves show three thermal events related to the three stages of loss of mass of the co-amorph. The first event is located in region I, starting at 37.76°C, whose mass loss corresponds to the dehydration of the material and is equivalent to 0.045 mg, about 1.049% of the initial mass. The second mass loss stage corresponds to the decomposition starting at 131.85°C with a mass loss of 1.286 mg (29.977% of the initial mass). This decomposition temperature indicates the stability of the sample. The third stage corresponds to the continuation of the decomposition of the material which resulted in a mass loss of 0.786 mg (18.322% of the initial mass) and started at 231.26°C. Thus, from the analysis it was verified that the co-amorphous presents good thermal stability with decomposition beginning at 131.85°C. The co-amorphous DTA Curve (1: 3) showed two thermal events. The first is characteristic of dehydration starting at 37.89°C, and the second event can be attributed to material decomposition at 131.85°C.

[0022] The DSC curve of the co-amorphous RIF-OXA (1: 3) did not show any thermal event that could be identified, although a well-defined glass transition temperature (Tg) was expected for amorphous material, with the need for further analysis to identify this thermal property of the material. However, there is no melting event of the material in the DSC curve, confirming its amorphous state. The measurements for the characterization of the material by the different techniques demonstrate that the methodology used successfully promotes the drug: coformer interaction to obtain the co-amorphous material.

[0023] This amorphous solid dispersion of RIF presents itself as a very promising alternative for improving the treatment of leprosy and tuberculosis, considering that amorphous materials are more water soluble than crystalline pharmaceutical materials (ALMEIDA et al, 2012) . Consequently, the RIF present in the co-amorph tends to have greater bioavailability and therapeutic efficacy in the treatment of these diseases in relation to the RIF in its crystalline form. ALMEIDA, H.; AMARAL, M. H.; LOBÃO, P: Comparative study of sustained-release lipid microparticles and solid dispersions containing ibuprofen. Brazilian Journal of Pharmaceutical Sciences, v. 48, no. 3, p. 529-536, 2012.

Claims (4)

SOLID DISPERSION OF THE ANTIBIOTIC RIFAMPICIN, obtained using the slow solvent evaporation method, characterized in that it is obtained from a polymorph of the drug Rifampicin (RIF) with oxalic acid (OXA) as a coformer. SOLID DISPERSION OF THE ANTIBIOTIC RIFAMPICIN, according to claim 1, characterized in that it is obtained in the molar ratio 1: 3 (drug: coformer). SOLID DISPERSION OF THE ANTIBIOTIC RIFAMPICIN, according to claims 1 and 2, characterized in that it uses methanol (MeOH) as solvent to obtain the co-amorph. SOLID DISPERSION OF THE ANTIBIOTIC RIFAMPICIN, according to claims 1 to 3, characterized by using the X-Ray Diffraction technique by the Powder Method (DRXP); Thermogravimetry, Derivative Thermogravimetry and Simultaneous Differential Thermal Analysis (TG-DTG/DTA) and Differential Scanning Calorimetry (DSC) to characterize the material.

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