Sustained-release solid dispersion

Higuchi, T. Mechanism of sustained release medication Theoretical analysis of rate of release of solid drugs dispersed in solid matrices. J. Pharm. Sci. 52 1145—1149, 1963. 

The carriers used in the production of sustained-release matrix tablets of water-soluble drugs by melt-congealing share some of the characteristics of carriers used for hot-melt coating and solid dispersion... 

Controlled-release formulations of acetaminophen, aminopyrine, chlorpheniramine maleate, and salicylic acid that use Eudragit RSPM as a water-insoluble carrier, prepared by the solvent method, have been reported. A novel approach that uses a less soluble derivative of the drug as a carrier was used by Yang and Swarbrick to prepare sustained-release solid dispersions of dapsone. 

Component of controlled-release or sustained-release dosage forms enteric coating agent film-forming agent solid dispersion vehicle. 

Aquacoat ECD and Surelease are two commercially available ethylcellulose pseudolatex dispersions. Aquacoat ECD. a product of FMC Corporation, is produced by an emulsification/solvent evaporation proce.ss that utilizes sodium lauryl sulfate and cetyl alcohol as colloid. stabilizers (64). The Aquacoat ECD dispersion contains approximately 27% ethylcellulose and 30% total solids. The dispersion does not contain plasticizer, and therefore an appropriate plasticizer must be added to the dispersion prior to coating. The dispersion is typically diluted to a final solids content in the range of 15-20% prior to spray coating. Although, intended to be a pH-independent sustained release coating system, the content of sodium lauryl sulfate in the Aquacoat ECD dispersion has been demonstrated to cause reduced drug release rates in acidic media versus media of neutral pH (65.66). 

Nonimmediate- or sustained-release devices can be divided into two categories. The first is a reservoir device whereby the dmg is loaded into the reservoir as either a solid or a liquid. Dmg release occurs by diffusion through either a semipermeable membrane or a small orifice. Lasers are commonly used to generate uniform orifices through which the dmg will diffuse. Osmotic pressure is commonly used to provide the driving force for dmg dispersion. The second is a matrix diffusion device whereby the dmg is dispersed evenly in a solid matrix. Polymers are commonly used as the matrix. Dmg delivery is accomplished by either dissolution of the matrix, with corresponding release of dmg, or diffusion of the dmg from the insoluble matrix. 

Yuasa, H. Ozeki, T Kanaya, Y Oishi, K. Application of the solid dispersion method to the controlled release of medicine. II. Sustained release tablet using solid dispersion granule and the medicine release mechanism. Chem. Pharm. Bull. 1992, 40 (6), 1592-1596. 

The formulations of agrochemicals cover a wide range of systems which range from simple aqueous solutions (for water-soluble actives) and self-emulsifiable oils to disperse systems of suspensions, emulsions and microemulsions. More complex formulations such as multiple emulsions and suspoemulsions (mixtures of suspensions and emulsions) are also applied in some cases. Microencapsulation of active ingredients for controlled and sustained release represents a more sophisticated approach to the formulation of agrochemicals. Solid formulations of wettable powders, grains, granules and tablets are also used in many applications. 

Lipid-based systems can achieve sustained release by providing a barrier to diffusion of water, necessary for dissolution of solid protein dispersed in a hydrophobic matrix, and by a subsequent barrier to diffusion or convection of protein solution entrapped within the matrix. The rate-limiting step for aqueous solute release is often dissolution or disintegration of the lipid mass or particle. Factors affecting release of proteins from various matrices have been reviewed in detail by Pitt (1990a) and Park et a/.(1993). 

Ferguson et al. (1990), at Elanco, prepared various oiFwax depot injectables for sustained release ofbovine somatotropin. To thicken the oils, waxes were melted into the oils, which were then cooled and homogenized until uniform in consistency. Solid BST was dispersed into the viscous oil and wax mixture. Three combinations of BST, oil, and wax were formulated and injected into dairy cattle, and these formulations gave sustained... 

Tanaka N, Imai K, Okimoto K, Ueda S, Tokunaga Y, Ibuki R, HigaM K, Kimura T (2006) Development of novel sustained-release system, disintegration-controlled matrix tablet (DCMT) with solid dispersion granules of ndvadipine (II) in vivo evaluation. J Control Release 112 51-56... 

Cur F., Yang M., Jiang Y., Cun D., Lin W., Fan Y., Kawashima Y (2003). Design of sustained-release nitrendipine microspheres having solid dispersion structure by quasiemulsion solvent diffusion method. Journal of ControlledRelease, 91,375-384. 

Also known as bhara gum, the exudate from the incised trunk of some tropical trees of Terminalia genus (T. bellerica Roxb., T. catappa L., T. randii Baker f.), Combretaceae family, may be used in the formulation of some sustained release pharmaceutical forms famotidine microcapsules (ionic gelation technique) [296] dextromethorphan hydrobromide tablets obtained by direct compression, wet granulation and solid dispersion techniques [297] carvedilol (water insoluble) and theophylline (water soluble) tablets prepared by direct compression - Terminalia gum was assessed as controlled release matrix against xanthan gum and hydroxypropyl methylcellulose [298]. 

Uses Lubricant for sustained release tablets emulsion stabilizer dispersant for pigments emulsifier in phannaceulicals Features Lipophilic matrix for oral solid dosage forms Regulatory USP, Ph.Eur, JCIC compliant Properties Off-wh. powd. sol. in fats, oils, waxes m.p. 54-64 C Imwitoi 928 [Sasol Gennany Sasol N. Am.)... 

---