Effect of drug properties on the release from CAP microspheres prepared by a solvent evaporation method

Abstract

Drugs with different water-solubility and molecular weights were microencapsulated in cellulose acetate phthalate, using an emulsion-solvent evaporation technique with a continuous oil-phase. The mean size of the particles was approximately 600 microns, and they were non-porous. The capacity of the microspheres to retain the drugs was evaluated by in vitro release studies in acidic medium. For low molecular weight compounds the release rates increased with solubility: for thiamin hydrochloride and phenacetin, a highly and a poorly soluble compound respectively, the percentages released at 60 min were 90 and 10%. Drugs with molecular weights above approximately 700 Da were retained in the microspheres. The above dependence on solubility was corroborated by release studies in ethanol, and by modelling the release of phenacetin in acidic media. Microspheres with a different polymer matrix, Eudragit RS PO, were also prepared by a similar technique, and these particles prolonged the release of thiamin for over 6 h, under simulated GI conditions.

Inhibiting the Gastric Burst Release of Drugs from Enteric Microparticles: The Influence of Drug Molecular Mass and Solubility

“…6). A larger molecular size of the drug is likely to impede its movement through the polymeric network of the microparticle matrix and hence its release in acid medium 7 . The relative importance of the two drug properties, molecular weight and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Other factors not investigated in this study are also expected to affect drug release from polymeric matrix systems such as drug-polymer interactions 18-21 .…”

“…In in vitro dissolution tests, enteric formulations may release no more than 10% of their drug content during a two-hour incubation in 0.1N HCl, and subsequently should release more than 80% of their drug content within 45 min of changing the dissolution medium to intestinal conditions. While drug release in intestinal conditions is easily achieved given that readily suspended microparticles have a large surface area, minimising/inhibiting drug release in acidic conditions has proven challenging, and insufficient control of drug release from microparticles in acid media has been reported [4][5][6][7][8][9][10] .…”

“…The aim of the work described in this paper was therefore to explore the relative importance of three drug and particle properties that have been directly related to drug release in gastric conditions 6,7,15 , namely, drug molecular weight and its solubility in acid, and microsphere size. Using an efficient o/o emulsion solvent evaporation method developed in our laboratory 13,16 , small uniform-size microparticles loaded with one of nine drug molecules of different physicochemical properties were produced using two different F o r P e e r R e v i e w 4 pH responsive polymers; Eudragit S and Eudragit L (pH thresholds 7.0 and 6.0 respectively).…”

Microparticles for delivering therapeutic peptides and proteins to the lumen of the small intestine

“…CAP microparticles were prepared by a simple emulsion, solvent evaporation method, based on the ones reported by Silva and Ferreira [7]. The polymer was dissolved in 10:1 mixtures (20 ml) of acetone/98% ethanol, at a 5±10% (w/v) concentration.…”

Liberação controlada da eosina impregnada em microesferas de copolímero de quitosana e poli(ácido acrílico)

“…Durante esse período, a indústria farmoquímica se destacou no uso e no aproveitamento de matérias primas de baixo custo e fácil acesso para o desenvolvimento de novos materiais poliméricos, o que permitiu o uso de várias técnicas para encapsulamento de muitos compostos em sistemas de multipartículas, como microesferas e microcápsulas, no intuito de proteger, estabilizar, mascarar os sabores indesejáveis ou modificar as propriedades de liberação [1] . Os sistemas de multipartículas têm suscitado um grande interesse nas formulações orais por apresentarem muitas vantagens, tais como dose única, variabilidade do tempo de trânsito no trato gastrointestinal e a possibilidade de mistura de fármacos de diferentes propriedades de liberação [2,3] . A quitosana (Figura 1), polissacarídeo obtido pela hidrólise alcalina da quitina [4] , age como floculante em tratamentos de efluentes líquidos e como resina quelante na remoção de metais pesados [5][6][7] .…”