Coating drug loading

Surface coating of mesoporous silicas provides an effective and flexible way for controlled release due to the high drug loading possible and the easy control of release rate. A drug-containing core or tablet is... 

That said, the task should not be overcomplicated, and many good instances exist to illustrate successful conclusions to such efforts. For example, the data shown in Table 12 illustrate the scaling-up of the Wurster process in which an aqueous latex coating has been applied to drug-loaded pellets in order to prepare a modified-release product. It is appropriate to point out that since the 32" Wurster essentially comprises three 18" Wurster units, the airflow used in the former represents approximately a threefold increase over that of the latter, with the result that the spray rate is scaled... 

Table 12 Coating Process Conditions Used in the Scaling-Up of the Wurster Process for Application of an Aqueous Latex Coating to Drug Loaded Pellets...

Effective product and process optimization play a prominent role in any successful scale-up study. As an illustration, this case study summarizes the initial development, and subsequent scale-up, of a Wurster process designed to facilitate the application of an aqueous ethylcellulose dispersion to drug-loaded pellets. At the same time, it was intended to deal, up front, with some of the idiosyncrasies of such a coating system that often influence the functionality of the final dosage form. 

Table 13 Process Variables Used in the Development and Optimization of a Coating Process Designed for the Application of a Modified-Release Film Coating to Drug-Loaded Pellets...

When ketoprofen was loaded with chitosan-coated ethylcellulose microparticles and the plain ethylcellulose microparticles, similar findings were obtained. Although ketoprofen is well absorbed from the GI tract, chitosan appears to influence the absorption profile. Chitosan allowed the particles to make contact with the mucosal membrane and be retained at adhesive sites, which means that the drug remains in the small intestine longer. This facilitated the absorption of ketoprofen in chitosan-coated microparticles loaded with ketoprofen. Chitosan is considered to improve the absorption properties of plain microparticles [33]. 

CGP 57813 is a peptidomimetic inhibitor of human HIV-1 protease. This lipophilic compound has been successfully entrapped in polylactic acid (PLA) and into pH-sensitive methacrylic acid copolymer particles (EUDRAGIT L 1 GO-55) [69], After the application of a film-coating, the plasma concentration was acceptable and reached similar levels as with injections of drug-loaded PLA carriers. To hinder the proteolytic degradation of a drug, two types of enteric-coated pellets were applied simultaneously. One contained the protease inhibitor coated... 

Although drug-loaded stents have shown beneficial effects on restenosis and thrombosis compared to bare stents in clinical trials and real-world practice, there are still concerns about their long-term safety and efficacy. It has been reported that clinical trials of drug-eluting stents were stopped because of increased (sub)acute thrombosis and neointimal growth or insufficient efficacy. Furthermore, increased late thrombosis has been reported, especially with cytotoxic drug-coated... 

The above procedure was also employed to investigate buccal absorption from the HEMAC experimental delivery device. As in the case of the diffusion cell the drug-loaded disc was positioned on the inner central surface of the buccal mucosa. An impermeable film coated with mucosal adhesive (F-4000, Adhesives Research, Glen Rock, PA) on the periphery was then positioned over the HEMAC disc to prevent dehydration and to secure the device in place on the mucosal surface. The disc was allowed to remain in contact with the mucosa for 4 h before it was removed for quantitation of residual drug content. Blood samples were collected over the same interval as for the saturated solution and processed in the same manner. 

When drug solubility is very high or drug loading is below the drug solubility, Equation (6.131) is applied to the perforated, coated tablets. Due to the diffusion term in Equation (6.131), the drug release kinetics are linear for the perforated, coated tablets. Figure 6.36 shows the release of diltiazem HC1 from the perforated, coated tablets. 

A coated, perforated donut-shaped tablet was proposed to deliver a water-soluble drug for 20 hr. A water-soluble polymer was incorporated to carry the drug. The erosion rate constant of 6.6 mg/cm2 hr was measured. The size of a tablet was 1.2 cm. Calculate the central hole size of the tablet to deliver the drug for 20 hr. Drug loading is 300 mg/cm3. 

Bhagwatwar, H. Bodmeier, R. The coating of drug-loaded sgura beads with various wax formulations. Pharm. Res. 1989, 6, PT 713-S-73. 

Cellulose acetate is used as a semipermeable coating on tablets, especially on osmotic pump-type tablets and implants. This allows for controlled, extended release of actives. Cellulose acetate films, in conjunction with other materials, also offer sustained release without the necessity of drilling a hole in the coating as is typical with osmotic pump systems. Cellulose acetate and other cellulose esters have also been used to form drug-loaded microparticles with controlled-release characteristics. 

Lee BJ, Ryn SG, Cui JH. Controlled release of dual drug loaded hydroxypropyl methylcellulose matrix tablet using drug containing polymeric coatings. Int ] Pharm 1999 188 71-80. 

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