High efficiency dry coating of non-subcoated pellets for sustained drug release formulations using amino methacrylate copolymers.

Dry coating utilizing a fluidized bed was evaluated in order to produce films with sustained drug release using amino methacrylate copolymers as film former. In contrast to other dry coating procedures using amino methacrylate copolymers, the described method enables an appropriate polymer adhesion by the selection of a plasticizer additive mixture in combination with the use of a three-way nozzle for simultaneous application. Well spreading fatty acid esters were found to increase the coating efficiency from 73% to approximately 86%, when they were used in conjunction with the plasticizer. Pellets were used as drug cores without previous treatment. After a curing step at 55 °C, the pellets exhibited a prolongation of the drug release over a period of about 6 h. Mainly the three parameters, coating level, composition of the polymers in the coating mixture, and the type of plasticizer, were found to exert distinct influence on the dissolution profile. Despite the differences in the coating procedure, the dissolution profiles of the coated pellets as well as the influencing parameters were similar to those known from conventional coating techniques.

Solubility parameters of hypromellose acetate succinate and plasticization in dry coating procedures.

Solubility parameters of HPMCAS have not yet been investigated intensively. On this account, total and three-dimensional solubility parameters of HPMCAS were determined by using different experimental as well as computational methods. In addition, solubility properties of HPMCAS in a huge number of solvents were tested and a Teas plot for HPMCAS was created. The total solubility parameter of about 24 MPa(0.5) was confirmed by various procedures and compared with values of plasticizers. Twenty common pharmaceutical plasticizers were evaluated in terms of their suitability for supporting film formation of HPMCAS under dry coating conditions. Therefore, glass transition temperatures of mixtures of polymer and plasticizers were inspected and film formation of potential ones was further investigated in dry coating of pellets. Contact angles of plasticizers on HPMCAS were determined in order to give a hint of achievable coating efficiencies in dry coating, but none was found to spread on HPMCAS. A few common substances, e.g. dimethyl phthalate, glycerol monocaprylate, and polyethylene glycol 400, enabled plasticization of HPMCAS; however, only triethyl citrate and triacetin were found to be suitable for use in dry coating. Addition of acetylated monoglycerides to triacetin increased coating efficiency, which was likewise previously demonstrated for triethyl citrate.

The role of capillary force promoters in dry coating procedures--evaluation of acetylated monoglyceride, isopropyl myristate and palmitate.

Previous studies described several dry powder coating procedures. Most of these techniques used polymer powders and plasticizers for attaining film formation. Thermo analytical methods showed that some of the used plasticizers did not reduce the glass transition temperature of the polymer markedly and consequently did not act as a plasticizer in a typical way. Further studies suggested that these substances were promoting capillary forces between the polymer particles thereby promoting the adhesion of the polymer on the cores and enhancing the coating efficiency. In this study these substances will be called capillary force promoters (CFP). The aims of this study are to evaluate the effectiveness of acetylated monoglyceride, isopropyl myristate and palmitate in terms of coating efficiency enhancement and to shape the idea about the way of action of CFPs in dry coating procedures. One of the main features of a good CFP represents its ability not to be taken up by the polymer but to remain on the polymer's surface being able to build up interparticle capillary forces. A CFP is further characterised by a good spreadability on the polymer. In this context, the lowering of the glass transition temperature has been found to be a good indicator for the affinity of the CFP to the polymer and its uptake by the polymer, whereas the contact angle between the polymer and the CFP represents a measure of its spreadability.