Production of Carbopol® 974P and Carbopol® 971P Pellets by Extrusion‐Spheronization: Optimization of the Processing Parameters and Water Content

Use of к-carrageenan, chitosan and Carbopol 974P in extruded and spheronized pellets that are devoid of MCC

The search for excipients to replace microcrystalline cellulose (MCC) in the production of pellets by extrusion-spheronization in cases of drug incompatibility or the lack of pellet matrix disintegration forms the basis of this study. A combination of к-carrageenan as a spheronization aid, chitosan as a diluent and Carbopol(®) 974P as a binder in the production of pellets containing no MCC has been investigated using acetaminophen as a model drug. Design of experiments allowed assessment of formulation and processing effects on pellet responses that included size, shape, fines, yield and friability. Statistical analysis revealed that the main factors and some of the two-factor interactions had a significant effect on pellet characteristics. Formulations containing high levels of к-carrageenan required more water to produce a wetted mass with good extrudability and extrudate capable of being spheronized. Although only a low level of Carbopol was used in the formulation, it imparted cohesiveness to the wetted mass as well as the extrudate. Furthermore, it was discovered that Carbopol could act as an extrusion aid, enabling the wetted mass to flow easily through the extruder screen holes without building up heat. Spherical and rugged pellets were produced that met the immediate release criterion.

Rheological, mucoadhesive and textural properties of thermoresponsive polymer blends for biomedical applications

The development of binary polymeric mixtures (polymer blends) containing bioadhesive and thermoresponsive polymers can provide new materials for biomedical applications, with higher contact, increased adhesion, prolonged residence time, protection, and in determined cases, secured absorption of an active agent from the site of application. Mixtures were prepared using a wide range of poloxamer 407 and Carbopol 971P(®) amounts. The rheological (flow and oscillatory), sol-gel transition temperature, mechanical (hardness, compressibility, adhesiveness, cohesiveness and elasticity), softness, and mucoadhesive properties of formulations were investigated. Moreover, the interaction between the different proportions of polymers was also analyzed. Continuous shear and oscillatory rheometry identified the plastic flow with various degrees of thixotropy, besides the viscoelastic behavior of formulations. The determination of gelation temperature displayed values ranged from 27.17 to 41.09°C. It was also found that low carbomer concentrations were enough to provide positive interaction parameter. However, the highest values were obtained for the polymeric blends with higher concentration of poloxamer 407. The mucoadhesion and softness index were greater in preparations containing 20% (w/w) poloxamer 407. The rheological, mechanical and mucoadhesive properties of the polymeric blends can be manipulated by changing the concentrations of the polymers and they suggest the blends are worthy of biomedical applications.

Formulation of bioadhesive hexylaminolevulinate pellets intended for photodynamic therapy in the treatment of cervical cancer

Photodynamic therapy has a great potential in the treatment of cervical cancer. The aim of this study was to develop bioadhesive pellets containing hexylaminolevulinate (HAL), a precursor of the photoactive substance PpIX, with a fast release for vaginal drug delivery. Pellets were produced by extrusion/spheronization, and Carbopol(®) 934 was used to obtain bioadhesive properties. A 2(2)-factorial design with center point investigating the HAL content (1 and 10%, w/w) and Carbopol(®) 934 content (1 and 8%, w/w) was set up. The most suitable formulations were mechanically stable and showed bioadhesive properties toward vaginal tissue. The drug load was released within 20 min in phosphate buffer pH 4 and 6.8 in the in vitro dissolution test. The stability of HAL in the pellet formulations varied, but the most stable formulation showed 96-97% HAL remaining in the formulation after 6-7 weeks of storage at accelerated temperature conditions (40 °C). The investigated formulations seem promising for vaginal delivery of HAL.