Thermal analysis and solution calorimetry studies on losartan polymorphs

Development of Losartan Orally Disintegrating Tablets by Direct Compression: a Cost-Effective Approach to Improve Paediatric Patient's Compliance

The development of suitable dosage forms is essential for an effective pharmacological treatment in children. Orally disintegrating tablets (ODTs) are attractive dosage forms that avoid swallowing problems, ensure dosage accuracy and are easy to administer as they disintegrate in the oral cavity. This study aimed to develop ODTs containing losartan potassium (LP) for the treatment of arterial hypertension in children. The ODTs, produced by the cost-effective manufacturing process of direct compression, consisted of a mixture of diluent, superdisintegrant, glidant and lubricant. Five superdisintegrants (croscarmellose sodium, two grades of crospovidone, sodium starch glycolate and pregelatinized starch) were tested (at two concentrations), and combined with three diluents (mannitol, lactose and sorbitol). Thus, thirty formulations were evaluated based on disintegration time, hardness and friability. Two formulations, exhibiting the best results concerning disintegration time (< 30 s), hardness and friability (≤ 1.0%), were selected as the most promising ones for further evaluation. These ODTs presented favourable drug-excipient compatibility, tabletability and flow properties. The in vitro dissolution studies demonstrated 'very rapid' drug release. Preliminary stability studies highlighted the requirement of a protective packaging. All quality properties retained appropriate results after 12 months of storage in airtight containers. In conclusion, the ODTs were successfully developed and characterised, suggesting a potential means to accomplish a final prototype that enables an improvement in childhood arterial hypertension treatment.

A New, More Stable Polymorphic Form of Otilonium Bromide: Solubility, Crystal Structure, and Phase Transformation

A new polymorphic form of otilonium bromide is presented (Form I), and a thorough analysis of its crystal and molecular structure is performed. The compound suffers a temperature-driven first-order phase transition at about 396 K, which transforms it into the polymorph reported by Dapporto P and Sega A (Acta Cryst. 1986;C42:474-478) (Form II). Through thermal analysis and solubility experiments the relative stability of both crystal modifications were determined, confirming that at room temperature this new Form I is the more stable one, Form II existing just in a metastable state.

Polymorphism: an evaluation of the potential risk to the quality of drug products from the Farmácia Popular Rede Própria

Polymorphism in solids is a common phenomenon in drugs, which can lead to compromised quality due to changes in their physicochemical properties, particularly solubility, and, therefore, reduce bioavailability. Herein, a bibliographic survey was performed based on key issues and studies related to polymorphism in active pharmaceutical ingredient (APIs) present in medications from the Farmácia Popular Rede Própria. Polymorphism must be controlled to prevent possible ineffective therapy and/or improper dosage. Few mandatory tests for the identification and control of polymorphism in medications are currently available, which can result in serious public health concerns.

Phase quantification of antihypertensive drugs - Chlorthalidone, Hydrochlorothiazide, Losartan and combinations, Losartan/Chlorthalidone and Losartan/Hydrochlorothiazide - by the Rietveld method

The identification and quantification of crystalline phases of antihypertensive drugs - Losartan potassium (LOS-K), Hydrochlorothiazide (HCTZ) and Chlorthalidone (CTD) were carried out by means of X-ray powder diffraction data and the Rietveld method. Quantitative phase analyses of Losartan potassium/Chlorthalidone (LOS-K/CTD) and Losartan potassium/Hydrochlorothiazide (LOS-K/HCTZ) combinations were also evaluated. The results indicated that for diuretics (HCTZ and CTD) only one crystalline phase was found in samples, and for LOS-K the crystal structure showed similarity between the Bragg peaks to the phase described as monoclinic and space group P21/c. After one year storage, the orthorhombic one was also observed in this sample.

Understanding the Polymorphic Behavior of Sibenadet Hydrochloride through Detailed Studies Integrating Structural and Dynamical Assessment

Three polymorphs of sibenadet hydrochloride (AR-C68397AA, Viozan) have been shown to exist at ambient temperature and have been characterized. Each undergoes a solid-state transition to a common high temperature form, which melts at approximately 220 degrees C. X-ray powder diffraction (XRPD) indicates that Polymorphs I and II share a similar layered structure not exhibited by Polymorph III. All three ambient temperature polymorphs show evidence of varying degrees of dynamic disorder of the terminal phenyl group as shown by solid-state NMR spectroscopy. Furthermore, the carbons alpha to the ether link also undergo different rates of mobility in Polymorphs I and II. This variation in the extent of dynamic disorder results in an alteration in the short-range structure resulting in distinct polymorphs. Polymorph I is the thermodynamically stable form at room temperature as indicated by solution calorimetry and assessment by thermodynamically driven solution mediated phase transition studies. The present study aims to address the types of discriminatory data required to make a clear distinction between physical forms and define, unequivocally, the presence of polymorphism.

Determination of Amorphous Content of Lactose Samples by Solution Calorimetry

Earlies studies suggest that solution calorimetry can be used to determine the extent of amorphous content of drug and excipient, when the solubility and dissolution rate of the compound in the chosen solvent are reasonably high. In the present study, the use of solution calorimetry for assessment of amorphous content of a sample that is not completely dissolved in a solvent was evaluated. Physical mixtures of lactose and spray-dried lactose samples were analysed. The amorphous content of the physical mixtures and the spray-dried samples varied from 0% to 100% determined by isothermal microcalorimetry. The enthalpy of solution (delta(sol)H) was determined in water. The lactose samples were dissolved quickly in water. In addition, the enthalpy accompanied with an addition of a lactose sample in an over saturated aqueous solution (delta(sat)H) (prepared from the corresponding lactose sample) was determined. The lactose sample did not completely dissolve in the over saturated aqueous solution. An excellent correlation was observed between delta(sol)H and the amorphous content of the samples. Interestingly, there was a linear correlation also between delta(sat)H and the amorphous content of the samples. Further, a linear relationship was observed between the delta(sat)H and the delta(sol)H of the samples. Therefore, solution calorimetry may represent a rapid and simple method for determining the amorphous content also in samples that are not completely dissolved in the solvent.

Applications of modulated differential scanning calorimetry in preformulation studies

Characterization of the thermal properties of active pharmaceutical ingredients is critical in the selection of appropriate physical forms for development and defining proper manufacturing, handling and storage conditions of those chemical entities. Modulated differential scanning calorimetry (MDSC) has proven to be an effective tool in the thorough characterization of thermal behavior of compounds in preformulation studies. Selected applications of MDSC for various preclinical compounds are presented, thereby demonstrating the utility of this analytical method in the determination of glass transitions, characterization of desolvation and degradation processes as well as in the study of polymorphic transformations and crystallizations.

Identification of losartan degradates in stressed tablets by LC-MS and LC-MS/MS

Three unknown peaks were observed in the severely stressed losartan tablets (at 40 degrees C and 75% relative humidity for 3 years) analyzed by a stability indicating HPLC method. The sample solutions were subjected to liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis to obtain the chemical identities of these potential degradates. High accuracy and sensitivity of losartan and its degradates were obtained by using atmospheric pressure chemical ionization (APCI) technique in the LC-MS/MS analysis. Three trace level degradates (< or = 0.1%) were found to be the aldehyde and dimeric derivatives of losartan. The structural assignment was further confirmed by comparing the tandem mass spectra of the unknowns with those of the authentic materials of each corresponding degradate. Finally, the mechanistic pathways for the formation of the dimers are discussed.