Yingliang Ma

Dry coating, a novel coating technology for solid pharmaceutical dosage forms.

Dry coating is a coating technology for solid pharmaceutical dosage forms derived from powder coating of metals. In this technology, powdered coating materials are directly coated onto solid dosage forms without using any solvent, and then heated and cured to form a coat. As a result, this technology can overcome such disadvantages caused by solvents in conventional liquid coating as serious air pollution, high time- and energy-consumption and expensive operation cost encountered by liquid coating. Several dry coating technologies, including plasticizer-dry-coating, electrostatic-dry-coating, heat-dry-coating and plasticizer-electrostatic-heat-dry-coating have been developed and extensively reported. This mini-review summarized the fundamental principles and coating processes of various dry coating technologies, and thoroughly analyzed their advantages and disadvantages as well as commercialization potentials.

Sustained release coating of tablets with Eudragit® RS/RL using a novel electrostatic dry powder coating process

The objectives of this study were to develop an electrostatic dry powder coating process for sustained coating tablets with Eudragit(®) RS/RL and to investigate the effects of various factors and operating conditions on the coating process and drug release profile. A liquid plasticizer (triethyl citrate) was sprayed onto the surface of the tablets followed by spraying coating powder by an electrostatic spray gun. The powder coated tablets were cured at elevated temperature for a film formation. Liquid plasticizer played important roles in lowering down the glass transition temperature (T(g)) of the coating polymer and increasing the surface electrical conduction of tablet cores. Electrostatic assisted coating deposition was confirmed by the fact that higher coating level was obtained with electrical charging than the ones without it. The micrographs of scanning electron microscopy (SEM) of coated tablets showed that the film formation mainly occurred during the curing step. Higher curing temperature and longer curing time help enhance the film formation. The in vitro drug release profiles indicated that curing time, temperature, coating level and ratio of Eudragit(®) RS/RL were the main factors affecting the sustained release profile. The electrostatic dry powder coating process has been demonstrated to be an alternative for tablet sustained release coating with Eudragit(®) RS and RL.

A novel electrostatic dry powder coating process for pharmaceutical dosage forms: immediate release coatings for tablets.

An electrostatic dry powder coating process for pharmaceutical solid dosage forms was developed for the first time by electrostatic dry powder coating in a pan coater system. Two immediate release coating compositions with Opadry® AMB and Eudragit® EPO were successfully applied using this process. A liquid plasticizer was sprayed onto the surface of the tablet cores to increase the conductivity of tablet cores to enhance particle deposition, electrical resistivity reduced from greater than 1×10(13)Ωm to less than 1×10(9)Ωm, and to lower the glass transition temperature (T(g)) of the coating polymer for film forming in the pan coater. The application of liquid plasticizer was followed by spraying charged coating particles using an electrostatic charging gun to enhance the uniform deposition on tablet surface. The coating particles were coalesced into a thin film by curing at an acceptable processing temperature as formation was confirmed by SEM micrographs. The results also show that the optimized dry powder coating process produces tablets with smooth surface, good coating uniformity and release profile that are comparable to that of the tablet cores. The data also suggest that this novel electrostatic dry powder coating technique is an alternative to aqueous- or solvent-based coating process for pharmaceutical products.

A novel electrostatic dry coating process for enteric coating of tablets with Eudragit L100-55

An electrostatic dry coating process based on a liquid pan coater was developed for enteric coating of tablets with Eudragit® L 100-55. Two different liquid plasticizers of triethyl citrate (TEC) and PEG400 were used in the coating process. In contrast to TEC, PEG400 produced good powder adhesion and successful coating. DSC results showed that PEG400 lowered the glass transition temperature (Tg) of Eudragit® L 100-55 to a greater extent than TEC at the same blend ratio, indicating that PEG400 was more effective in plasticizing the polymer. PEG400 showed higher contact angle on both surfaces of tablet cores and coating powders as well as lower absorption into the tablet cores than TEC, suggesting that more PEG400 existed at the interface between tablet core and coating powders. The combination effects of higher plasticizing efficiency and more PEG400 available at the tablet surface produced higher plasticization of Eudragit® L 100-55, leading to the successfully initial powder adhesion. The powder adhesion was further enhanced by the electrostatically assisted coating process, as confirmed by the higher coating level and coating efficiency with electrical charging (60 kV) than the ones without it (0 kV). The micrographs of scanning electron microscopy and in vitro drug release tests of the coated tablets showed that higher curing temperature and longer curing time led to enhanced film formation and acid resistance. The electrostatic dry coating process has been demonstrated to be a promising process for enteric coating of tablets.

Applying a novel electrostatic dry powder coating technology to pellets.

The present study aimed to apply a novel dry powder technology to coat pellets with different coating materials grounded into fine powders. Piroxicam, a non-steroidal anti-inflammatory drug, was used as the active pharmaceutical ingredient (API). Eudragit® EPO, Eudragit® RS/RL and Acryl EZE were used as the coating materials to achieve immediate release, sustained release and delayed release, respectively. Three steps including preheating, powder adhesion and curing were carried out to form the coating film while liquid plasticizers were used to decrease the glass transition temperature of coating powders and also served to reduce the electrical resistance of pellets. Results of SEM indicated coating film could be better formed by increasing curing temperature or extending curing time. Dissolution tests showed that three different drug release profiles, including immediate release, sustained release and delayed release, were achieved by this coating technology with different coating formulations. And the dry powder coated pellets using this developed technology exhibited an excellent stability with 1 month at 40 °C/75% RH. The coating procedure could be shortened to within 120 min and the use of fluidized hot air was minimized, both cutting down the overall cost dramatically compared to organic solvent coating and aqueous coating. All results demonstrated that the novel electrostatic dry powder coating method is a promising technology in the pharmaceutical coating industry.

The development of a novel dry powder inhaler

A novel active and multi-dose dry powder inhaler (DPI) was developed and evaluated to deliver a small quantity (100-500 μg) of pure drug without any excipient. This dry powder inhaler utilized two compressed air flows to dispense and deliver drug powder: the primary flow aerosolizes the drug powder from its pocket and the secondary flow further disperses the aerosol. In vitro tests by Anderson Cascade Impactor (ACI) indicated that the fine particle fraction (FPF) (<4.7 μm) of drug delivery could reach over a range of 50-70% (w/w). Emitted dose tests showed that delivery efficiency was above 85% and its relative standard deviation (RSD) was under 10%. Confocal microscopy was used to confirm the deposition of fluorescently labeled spray-dried powder in rabbit lungs. Also, a chromatographic method was used to quantify drug deposition. The results of animal tests showed that 57% of aerosol deposited in the rabbit lung and 24% deposited in its trachea. All the results implied that this novel active dry powder inhaler could efficiently deliver a small quantity of fine drug particles into the lung with quite high fine particle fraction.

Dry powder coated osmotic drug delivery system

ABSTRACT Dry powder coated osmotic drug delivery system (ODDS) were prepared and characterized using an innovative powder coating technology. Coating powder adhesion to the surface of the ODDS core was firstly performed through an electrostatic spray gun, followed by a curing step to allow those electrically deposited particles coalesce and form a continuous, uniform and strong coating film, which is the semipermeable membrane of the ODDS. Triethyl citrate (TEC) was found to be a better liquid plasticizer than PEG 400 both in reducing the glass transition temperature of the coating polymer (cellulose acetate) and in increasing the electrical conductivity of the ODDS cores, both of which led to an enhanced coating powder adhesion and film formation. Results of SEM indicated that the uniformity of the coating film varied significantly with the difference of curing time and temperature. Salbutamol sulfate and ibuprofen were used as the model drugs. Release profiles of both showed that zero‐order drug release kinetics was achieved. Release rate of both drugs from powder coated ODDS could be adjusted by changing the coating level but was independent of the agitation speed and of the pH of the release media. Graphical abstract Figure. No Caption available.