Sustained release properties

Antipov AA, Sukhorukov GB, Donath E et al (2001) Sustained release properties of polyelectrolyte multilayer capsules. J Phys Chem B 105 2281-2284... 

One final point concerns the prevention of the inevitable release of active molecules into the external phase during storage in sustained release systems, referred to earlier. One potential way around this is to use a double-shell system. Here the inner shell imparts the sustained release properties, but the outer shell is impenetrable to the active molecules. Triggered breaking of this outer shell, at the required point in a given process, would then initiate the sustained release process. This topic is the focus of our current research in this subject. 

Many new pharmaceutical agents are being formulated as viscous liquids, both because the molecule is often large and the formulation needs to be concentrated enough to be within a certain volume limit to be injected comfortably or to confer some sustained-release property of the formulation. 

Various lipids including triglycerides (e.g., trilaurin, trimyristin, tripalmitin and tristearin) and fatty acids were evaluated as carrier materials in sustained-release insulin implants. The drug/wax powder blend was compressed into a disc and implanted subcutaneously into Wistar rats. Monoglycerides tested eroded too fast and were not suitable. The triglycerides only sustained-the insulin release briefly. The best sustained-release properties were obtained with palmitic and stearic acids as the carrier materials. 

In a modified melt-dispersion method, sulfamethoxazole particles were dispersed in heated water, and powdered beeswax was added. The molten wax droplets collected the drug particles, and spherical agglomerates with sustained-release properties were obtained after cooling. Alternatively, the agglomerates could also be formed at room temperature by using solutions of the wax in a water-immiscible solvent. ... 

Gursoy A, Cevik S. Sustained release properties of alginate microspheres and tabletted microspheres of diclofenac sodium. ] Microencapsul 2000 17(5) 565-575. 

Smith HA, Evanson RV, Sperandio GJ. The development of a liquid antihistaminic preparation with sustained release properties. 

Tegretol XR product loses its sustained-release properties if broken or chewed... 

Onofre, F.O. Mendez-Montealvo, G. Wang, Y.J. Sustained release properties of cross-linked corn starches with varying amylose contents in monolithic tablets. Starch/Starke 2010, 62 (3-4), 165-172. 

Sun W, Peng W, Li G, Jiang T (2011) Design, synthesis, and sustained-release property of 1,3-cyclic propanyl phosphate ester of 18 beta-glycyrrhetinic acid. Chem Biol Drug Des 77 206-211... 

Citric acid esters are discussed in the review papers, patents, and conunercial litera-ture. ° " " Citric acid based plasticizers are one of the major contenders to replace phtha-lates (especially targeted to replace DOP). ° Some properties of materials plasticized with citrates can match those of DOP plasticized PVC but the cost of their production is substantially higher. Citrates are extracted from flexible PVC at a higher rate than DOP and trimellitates." Eudragit, which is a choice polymer in pharmaceutical coatings, having controlled release or sustained release properties, performs its functions very well when plasticized with triethyl citrate.The concentration of plasticizer can be used as the parameter that regulates the release rate. 

Valarezo, E., Tammaro, L., Gonzalez, S., Malagon, O., and Vittoria, V. (2013) Fabrication and sustained release properties of poly(e-caprolactone) electrospun fibers loaded with layered double hydroxide nanoparticles intercalated with amoxicillin. Appl. Clay Set, 72, 104-109. 

Parida P, Dash D, Behera A, Mishra SC. Preparation and characterization of graft biopolymer to improve sustained release property. National Conference on Processing and Characterization of Materials, Department of Metallurgical Materials Engineering, National Institute of Technology, Rourkela, India December 2, 2011. 

Site-specific delivery of the drugs Sustained release properties... 

Figure 6.3 Release profiles for (a) indomethacin and (b) lidocaine in 0.05M HCl in the free state ( ) and from GlPS- ra/ -P2VP copolymer ( ). Mt is the cumulative mass released at time t, and Mgq is the mass released at equilibrium. (Reprinted from Polymer, 49, G.N. Njikang, M. Gauthier and J. Li, Sustained release properties of arborescent polystyrene-grq/it-poly (2-vinylpyridine) copolymers, 5474-5481, 2008, with permission from Elsevier.)...

Njikang, G.N., Gauthier, M., and Li, J. (2008d) Sustained release properties of arborescent polystyrene-grq -poly (2-vinylpyridine) copolymers. Polymer, 49,5474-5481. 

E Onofre, Y.-J. Wang and A. Mauromoustakos, Effects of structure and modification on sustained release properties of starches, Carbohydr.Polym., 76 (4) 541-547, 2009. 

The authors reported the polymers to possess controlled/sustained release properties in biological fluids [238] [239], Puoci etal. also reported spherical MlPs for the controlled delivery of sulfasalazine using the same functional monomers and crosslinkers but a different initiator, i.e., 2,20-azoisobutyronitrile (AIBN) [242]. 

Due to its mucoadhesive and sustained-release properties, hakea gum (HG), obtained from the shrub Hakea gibbosa (Sm.) Cav. (Proteaceae), is used for the formulation of some buccal tablets containing chlorpheniramine maleate [242,243] or calcitonin [243]. Flat-faced Cutina-coated core tablets containing either 22/32 mg of HG, 25/40 mg of chlorpheniramine maleate and sodium bicarbonate/tartaric acid (1 1.5 molar ratio) were obtained by direct compression technique [243]. Also, an improved trans-buccal delivery system for therapeutic polypeptides obtained using direct compression technique supposes flat-faced Cutina-coated core tablets containing either 12/32 mg of HG and 40 pg (200 lU) of salmon calcitonin [244]. 

The major advantage of thermosensitive polymeric systems is the avoidance of toxic organic solvents, the ability to transport both hydrophilic and lipophilic drugs, reduced systemic side effects, site-specific drug delivery, and sustained release properties. 

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