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1.
The aim of the present research work was to develop release modulated beads of losartan potassium complexed with anion exchange
resin, Duolite AP143 (cholestyramine). Chitosan was selected as a hydrophilic polymer for the formation of beads which could
sustain the release of the drug up to 12 h, along with drug resin complex (DRC). Chitosan beads were prepared using an in-liquid
curing method by ionotropic cross-linking or interpolymer linkage with sodium tripolyphosphate (TPP). The formulation of the
beads was optimized for entrapment efficiency and drug release using 32 full factorial design. The independent variables selected were DRC/chitosan and percent of TPP. The optimization model was
validated for its performance characteristics. Studies revealed that as the concentration of chitosan and TPP was increased,
entrapment efficiency and the drug release were found to increase and decrease, respectively. The swelling capacity of chitosan–TPP
beads decreased with increasing concentration of TPP. The effect of chitosan concentration and percentage of TPP solution
used for cross-linking on entrapment efficiency and drug release rate was extensively investigated. Optimized beads were subjected
to in vivo studies in Wistar albino rats to determine the mean arterial blood pressure and compared with marketed formulation. The pharmacodynamic
study demonstrates steady blood pressure control for optimized formulation as compared to fluctuated blood pressure for the
marketed formulation. 相似文献
2.
Stomach-Specific Controlled Release Gellan Beads of Acid-Soluble Drug Prepared by Ionotropic Gelation Method 总被引:1,自引:0,他引:1
The purpose of the present work was the development and evaluation of stomach-specific controlled release mucoadhesive drug
delivery system prepared by ionotropic gelation of gellan beads, containing acid-soluble drug amoxicillin trihydrate, using
32 factorial design with concentration of gellan gum and quantity of drug as variables. The study showed that beads prepared
in alkaline cross-linking medium have higher entrapment efficiency than the acidic cross-linking medium. The entrapment efficiency
was in the range of 32% to 46% w/w in acidic medium, which increased up to 60% to 90% w/w in alkaline medium. Batches with lowest, medium, and highest drug entrapment were subjected to chitosan coating to form a
polyelectrolyte complex film. As polymer concentration increases, entrapment efficiency and particle size increases. Scanning
electron microscopy revealed spherical but rough surface due to leaching of drug in acidic cross-linking solution, dense spherical
structure in alkaline cross-linking solution, and rough surface of chitosan-coated beads with minor wrinkles. The in vitro drug release up to 7 h in a controlled manner following the Peppas model (r = 0.9998). In vitro and in vivo mucoadhesivity study showed that beads have good mucoadhesivity and more than 85% beads remained adhered to stomach mucosa
of albino rat even after 7 h. In vitro growth inhibition study showed complete eradication of Helicobacter pylori. These results indicate that stomach-specific controlled release mucoadhesive system of amoxicillin gellan beads may be useful
in H. pylori treatment. 相似文献
3.
A newly available polyvinylacetate aqueous dispersion, Kollicoat SR 30D, was evaluated with respect to its ability to modulate
the in vitro release of a highly water-soluble model compound (diphenhydramine hydrochloride) from nonpareil-based systems.
Kollicoat SR 30D premixed with a selected plasticizer (10% wt/wt propylene glycol, 2.5% triethyl citrate, or 2.5% dibutyl
sebacute), talc, and red #30 lake dye was coated onto the drug beads in an Aeromatic Strea I fluid-bed drier with a Wurster
insert using bottom spray. With propylene glycol as the plasticizer, increases in polymer coating level retarded drug release
from beads in a stepwise fashion along with apparent permeability, indicating a consistent release mechanisms. Stability studies
at 40°C/75% RH revealed gradual decreases in dissolution rate, and additional curing studies further confirmed the dependence
of release kinetics on curing condition. Furthermore, the type of plasticizer was found to play a key role. Unplasticized
formulations exhibited the fastest dissolution, followed by formulations plasticized with triethyl citrate, propylene glycol,
and dibutyl sebacate. All 4 formulations (unplasticized and plasticized), nevertheless, revealed a marked difference between
uncured and cured dissolution profiles. Kollicoat SR 30D has, thereby, been demonstrated to effectively retard drug release
from nonpareilbased systems. However, selected plasticizer type and subsequent curing condition play important roles in controlling
drug release from such a system. 相似文献
4.
Pornsak Sriamornsak Jurairat Nunthanid Kamonrak Cheewatanakornkool Somkamol Manchun 《AAPS PharmSciTech》2010,11(3):1315-1319
Drug-loaded calcium pectinate gel (CaPG) beads were prepared by either mixing, absorption, or swelling method. The effects of drug loading method as well as the drug loading factors (i.e., drug concentration, soaking time in drug solution, type of solvent) on drug content and drug release were investigated. The amount of drug uptake (i.e., drug content) into CaPG beads increased as the initial drug concentration increased and varied depending on the loading method. The in vitro release studies in 0.1 N hydrochloric acid (HCl) and pH 6.8 buffer indicated that the drug loading method affected drug release and release parameter, time for 50% of drug release (T 50). The mixing method provided a faster drug release and lower T 50 than the absorption method and swelling method, respectively. This is probably due to higher drug content in CaPG beads. The increased concentration of drug in soaking solution and soaking time resulted in higher drug content and thus faster drug release (lower in T 50 values). When using 0.1 N HCl as solvent for soaking instead of water, the drug release was slower owing to the increase in molecular tortuosity of CaPG beads. The drug release was also affected by pH of the release medium in which drug release in 0.1 N HCl was faster than in pH 6.8 buffer. 相似文献
5.
《Journal of Fermentation and Bioengineering》1992,73(4):319-322
The optimum concentrations of sodium alginate (wt. %), calcium chloride (M) and yeast cells (wt. %), and curing time (h) for enhanced gel stability were obtained employing a full factorial search. The results indicate that the concentrations of sodium alginate and CaCl2, and the curing time of the beads were found to have a pronounced effect on the stability of the beads. The cell concentration, on the other hand, has an adverse influence either individually or in combination with other variables. The path of steepest ascent method has been used to optimize the variables and the resultant gel beads were evaluated for fermentation ability. 相似文献
6.
Pasquale Del Gaudio Paola Russo Maria Rosaria Lauro Paolo Colombo Rita P. Aquino 《AAPS PharmSciTech》2009,10(4):1178-1185
In this paper, ketoprofen and ketoprofen lysinate were used as model drugs in order to investigate release profiles of poorly
soluble and very soluble drug from sodium alginate beads manufactured by prilling. The effect of polymer concentration, viscosity,
and drug/polymer ratio on bead micromeritics and drug release rate was studied. Ketoprofen and ketoprofen lysinate loaded
alginate beads were obtained in a very narrow dimensional range when the Cross model was used to set prilling operative conditions.
Size distribution of alginate beads in the hydrated state was strongly dependent on viscosity of drug/polymer solutions and
frequency of the vibration. The release kinetics of the drugs showed that drug release rate was related with alginate concentration
and solubility of the drug. Alginate solutions with concentration higher than 0.50% (w/w) were suitable to prepare ketoprofen gastro-resistant formulation, while for ketoprofen lysinate alginate, concentration
should be increased to 1.50% (w/w) in order to retain the drug in gastric environment. Differential scanning calorimetry thermograms and Fourier transform
infrared analyses of drug-loaded alginate beads indicated complex chemical interactions between carboxyl groups of the drug
and polymer matrix in drug-loaded beads that contribute to the differences in release profile between ketoprofen and ketoprofen
lysinate. Total release of the drugs in intestinal medium was dependent on the solubility of the drug and was achieved between
4 and 6 h. 相似文献
7.
The aim of this study was to examine the effect of pellet size, pectin type, pectin concentration, and dissolution medium on the swelling and drug release behavior of spherical pellets containing theophylline and coated with 2 different calcium pectinates, using a multi-level factorial design approach. The spherical pellets were prepared by an extrusion-spheronization method and then coated with calcium pectinate using the diffusion-controlled interfacial complexation technique, which provides a defect-free and uniform coating on solid cores. Theophylline release from the pellets was slowed by the application of the coatings. The time to release 50% of the payload (ie, T50) in an acidic medium was approximately 7 minutes from uncoated small pellets and was 55 minutes after an amidated calcium pectinate coat was applied; a comparable coat on large pellets showed a T50 of 93 minutes. Drug release profiles of dry coated pellets showed a lag time (all less than 20 minutes) when the gel coat hydrated and swelled, followed by a zero-order release. It was found that the release rate was controlled by the pellet size, pectin type, pectin concentration, and dissolution medium. 相似文献
8.
The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres
made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation
process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific
ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared
at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US
Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered
medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow
size distributions with one size fraction comprising 70–80% of the yield. Scanning electron microscopy and quantitative Fourier
transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs
of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution
results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly
basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted
to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism. 相似文献
9.
Angadi SC Manjeshwar LS Aminabhavi TM 《International journal of biological macromolecules》2012,51(1-2):45-55
Composite blend microbeads of sodium alginate (NaAlg) with sodium carboxymethyl cellulose (NaCMC) containing magnesium aluminum silicate (MAS) particles and enteric coated with chitosan have been prepared to achieve controlled release (CR) of amoxicillin in stomach environment. The composite beads have been characterized by X-ray diffraction (XRD) to study drug distribution, DSC for understanding thermal stability and Fourier transform infrared (FTIR) spectroscopy to investigate chemical interactions as well as to assess the structure of the drug-loaded formulations. Surface morphology of the beads was investigated by scanning electron microscopy (SEM). The size distribution of beads loaded with drug as studied by particle size analyzer was in the range of 745-889 μm. The beads exhibited quite widely varying encapsulation efficiencies from 52 to 92%. Equilibrium swelling of the beads measured in water and in vitro release of amoxicillin in pH 1.2 medium suggests that drug release depends on polymer blend composition, concentration of MAS and extent of enteric coating. 相似文献
10.
Amelt solidification technique has been developed to obtain sustained-release waxy beads of flurbiprofen. Low glass transition
temperature (t
g) and shear-induced crystallization of flurbiprofen made it a suitable candidate for melt solidification technique. The process
involved emulsification and solidification of flurbiprofen-cetyl alcohol melt at significantly low temperature (5°C). The
effect of variables, namely, the amount of cetyl alcohol and the speed of agitation, was studied using 32 factorial design. The technique and the beads were evaluated on the basis of process and desired yield, surface topography,
Fourier-transform infrared (FT-IR), differential scanning calorimetry (DSC), particle size distribution, crushing strength,
and drug release. Average values for process and desired yields were 97% wt/wt and 26% wt/wt, respectively. No interaction
was observed between drug and excipient. Multiple regression analysis was carried out, and response surfaces were obtained.
A curvilinear relationship was observed between percentage of desired yield and the amount of cetyl alcohol. Linear decrease
in crushing strength was observed with increase in the amount of cetyl alcohol. Drug released from the beads followed zero
order kinetics. Burst release was shown to a greater extent in beads containing a lower amount of cetyl alcohol. Response
surfaces of time required for certain percentage of drug (t
D%) showed that after critical concentration of about 20% of cetyl alcohol (400 mg/batch), no significant release retardant
effect was observed. 相似文献
11.
Bajerová M Krejčová K Rabišková M Muselík J Dvořáčková K Gajdziok J Masteiková R 《AAPS PharmSciTech》2011,12(4):1348-1357
The aim of this study was to develop novel hydrogel-based beads and characterize their potential to deliver and release a
drug exhibiting pH-dependent solubility into distal parts of gastrointestinal (GI) tract. Oxycellulose beads containing diclofenac
sodium as a model drug were prepared by the ionotropic external gelation technique using calcium chloride solution as the
cross-linking medium. Resulting beads were characterized in terms of particle shape and size, encapsulation efficacy, swelling
ability and in vitro drug release. Also, potential drug–polymer interactions were evaluated using Fourier transform infrared spectroscopy. The
particle size was found to be 0.92–0.96 mm for inactive (oxycellulose only) and 1.47–1.60 mm for active (oxycellulose–diclofenac
sodium) beads, respectively. In all cases, the sphericity factor was between 0.70 and 0.81 with higher values observed for
samples containing higher polymer and drug concentrations. The swelling of inactive beads was found to be strongly influenced
by the pH and composition (i.e. Na+ concentration) of the selected media (simulated gastric fluid vs. phosphate buffer pH 6.8). The encapsulation efficiency of the prepared particles ranged from 58% to 65%. Results of dissolution
tests showed that the drug loading inside of the particles influenced the rate of its release. In general, prepared particles
were able to release the drug within 12–16 h after a lag time of 4 h. Fickian diffusion was found as the predominant drug release mechanism. Thus, this novel particulate system showed
a good potential to deliver drugs specifically to the distal parts of the human GI tract. 相似文献
12.
This work examines the influence of various process parameters (like sodium alginate concentration, calcium chloride concentration,
and hardening time) on papain entrapped in ionotropically cross-linked alginate beads for stability improvement and site-specific
delivery to the small intestine using neural network modeling. A 33 full-factorial design and feed-forward neural network with multilayer perceptron was used to investigate the effect of process
variables on percentage of entrapment, time required for 50% and 90% of the enzyme release, particle size, and angle of repose.
Topographical characterization was conducted by scanning electron microscopy, and entrapment was confirmed by Fourier transform
infrared spectroscopy and differential scanning calorimetry. Times required for 50% (T50) and 90% (T90) of enzyme release were increased in all 3 of the process variables. Percentage entrapment and particle size were found to
be directly proportional to sodium alginate concentration and inversely proportional to calcium chloride concentration and
hardening time, whereas angle of repose and degree of cross-linking showed exactly opposite proportionality. Beads with >90%
entrapment and T50 of <10 minutes could be obtained at the low levels of all 3 of the process variables. The inability of beads to dissolve
in acidic environment, with complete dissolution in buffer of pH≥6.8, showed the suitability of beads to release papain into
the small intestine. The shelf-life of the capsules prepared using the papain-loaded alginate beads was found to be 3.60 years
compared with 1.01 years of the marketed formulation. It can be inferred from the above results that the proposed methodology
can be used to prepare papain-loaded alginate beads for stability improvement and site-specific delivery.
Published: September 30, 2005 相似文献
13.
The objective of this study was to develop a multiunit sustained release dosage form of diltiazem using a natural polymer
from a completely aqueous environment. Diltiazem was complexed with resin and the resinate-loaded carboxymethyl xanthan (RCMX)
beads were prepared by interacting sodium carboxymethyl xanthan (SCMX), a derivatized xanthan gum, with Al+3 ions. The beads were evaluated for drug entrapment efficiency (DEE) and release characteristics in enzyme free simulated
gastric fluid (SGF, HCl solution, pH 1.2) and simulated intestinal fluid (SIF, USP phosphate buffer solution, pH 6.8). Increase
in gelation time from 5 to 20 min and AlCl3 concentration from 1 to 3% decreased the DEE respectively from 95 to 79% and 88.5 to 84.6%. However, increase in gum concentration
from 1.5 to 2.5% increased the DEE from 86.5 to 90.7%. The variation in DEE was related to displacement of drug from the resinate
by the gel forming Al+3 ions. While 75–82% drug was released in 2 h in SGF from various beads, 75 to 98% drug was released in 5 hour in SIF indicating
the dependence of drug release on pH of dissolution media. Although the beads maintained their initial integrity throughout
the dissolution process in both media, as evident from scanning electron microscopic studies, the faster release in SGF was
accounted for higher swelling of the beads in SGF than in SIF. When release data (up to 60%) was fitted in power law expression,
the drug release was found to be controlled by diffusion with simultaneous relaxation phenomena. 相似文献
14.
M. Tavakol E. Vasheghani-Farahani T. Dolatabadi-Farahani S. Hashemi-Najafabadi 《Carbohydrate polymers》2009,77(2):326-330
In the present study, spherical beads were prepared from a water-soluble chitosan (N,O-carboxymethyl chitosan, NOCC) and alginate with ionic gelation method. Then, swollen calcium–alginate–NOCC beads were coated with chitosan. To prepare drug loaded beads, sulfasalazine (SA) was added to the initial aqueous polymer solution. The effect of coating, as well as drying procedure, on the swelling behavior of unloaded beads and SA release of drug loaded ones were evaluated in simulated gastrointestinal tract fluid. The rate of swelling and drug release were decreased for air-dried and coated beads in comparison with freeze-dried and uncoated ones, respectively. No burst release of drug was observed from whole tested beads. Chitosan coated beads released approximately 40% of encapsulated drug in simulated gastric and small intestine tract fluid. Based on these results, the chitosan coated alginate–NOCC hydrogel may be used as potential polymeric carrier for colon-specific delivery of sulfasalazine. 相似文献
15.
The aim of this study was to formulate a self-emulsifying system (SES) containing a lipophilic drug, loratadine, and to explore
the potential of preformed porous polystyrene beads (PPB) to act as carriers for such SES. Isotropic SES was formulated, which
comprised Captex 200 (63% wt/wt), Cremophore EL (16% wt/wt), Capmul MCM (16% wt/wt), and loratadine (5% wt/wt). SES was evaluated
for droplet size, drug content, and in vitro drug release. SES was loaded into preformed and characterized PPB using solvent
evaporation method. SES-loaded PPB were evaluated using scanning electron microscopy (SEM) for density, specific surface area
(SBET), loading efficiency, drug content, and in vitro drug release. After SES loading, specific surface area reduced drastically,
indicating filling of PPB micropores with SES. Loading efficiency was least for small size (SS) and comparable for medium
size (MS) and large size (LS) PPB fractions. In vitro drug release was rapid in case of SS beads due to the presence of SES
near to surface. LS fraction showed inadequate drug release owing to presence of deeper micropores that resisted outward diffusion
of entrapped SES. Leaching of SES from micropores was the rate-limiting step for drug release. Geometrical features such as
bead size and pore architecture of PPB were found to govern the loading efficiency and in vitro drug release from SES-loaded
PPB.
Published: March 24, 2006 相似文献
16.
Preparation and evaluation of chitosan/carrageenan beads for controlled release of sodium diclofenac
The polyelectrolyte complex (PEC) hydrogel beads based on chitosan (CS) and carrageenan (CR) have been studied as a controlled release device to deliver sodium diclofenac (DFNa) in the simulated gastrointestinal condition. Various factors potentially influencing the drug release (ie, CS/CR proportion, DFNa content, types and amount of cross-linking agents) were also investigated. The optimal formulation was obtained with CS/CR proportion of 2/1 and 5% (wt/vol) DFNa. The controlled release of the drug from this formulation was superior to other formulations and was able to maintain the release for approximately 8 hours. Upon cross-linking with glutaric acid and glutaraldehyde, the resulting beads were found to be more efficient for prolonged drug release than their non-cross-linking counterparts. The bead cross-linked with glutaraldehyde was able to control the release of the drug over 24 hours. The difference in the drug release behavior can be attributed to the differences in ionic interaction between the oppositely charged ions and to the concentrations of the drug within the beads, which depends on the compositions of the formulation and the pH of the dissolution medium. The release of drug was controlled by the mechanism of the dissolution of DFNa in the dissolution medium and the diffusion of DFNa through the hydrogel beads. 相似文献
17.
An objective of the present investigation was to prepare and evaluate Eudragit-coated pectin microspheres for colon targeting
of 5-fluorouracil (FU). Pectin microspheres were prepared by emulsion dehydration method using different ratios of FU and
pectin (1:3 to 1:6), stirring speeds (500–2000 rpm) and emulsifier concentrations (0.75%–1.5% wt/vol). The yield of preparation
and the encapsulation efficiencies were high for all pectin microspheres. Microspheres prepared by using drug:polymer ratio
1:4, stirring speed 1000 rpm, and 1.25% wt/vol concentration of emulsifying agent were selected as an optimized formulation.
Eudragit-coating of pectin microspheres was performed by oil-in-oil solvent evaporation method using coat: core ratio (5:1).
Pectin microspheres and Eudragit-coated pectin microspheres were evaluated for surface morphology, particle size and size
distribution, swellability, percentage drug entrapment, and in vitro drug release in simulated gastrointestinal fluids (SGF).
The in vitro drug release study of optimized formulation was also performed in simulated colonic fluid in the presence of
2% rat cecal content. Organ distribution study in albino rats was performed to establish the targeting potential of optimized
formulation in the colon. The release profile of FU from Eudragit-coated pectin microspheres was pH dependent. In acidic medium,
the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation
that Eudragit-coated pectin microspheres are promising controlled release carriers for colon-targeted delivery of FU.
Published: February 16, 2007 相似文献
18.
This investigation describes the development of an intragastric drug-delivery system for cefuroxime axetil. The 32 full factorial design was employed to evaluate contribution of hydroxypropyl methyl cellulose (HPMC) K4M/HPMC K100 LV ratio
(polymer blend) and sodium lauryl sulfate (SLS) on drug release from HPMC matrices. Tablets were prepared using direct compression
technique. Formulations were evaluated for in vitro buoyancy and drug release study using United States Pharmacopeia (USP) 24 paddletype dissolution apparatus using 0.1N HCl as a dissolution medium. Multiple regression analysis was performed for
factorial design batches to evaluate the response. All formulations had floating lag times below 2 minutes and constantly
floated on dissolution medium for more than 8 hours. It was found that polymer blend and SLS significantly affect the time
required for 50% of drug release, percentage drug release at 12 hours, release rate constant, and diffusion exponent (P<.05). Also linear relationships were obtained between the amount of HPMC K100 LV and diffusion exponent as well as release
rate constant. Kinetic treatment to dissolution profiles revealed drug release ranges from anomalous transport to case 1 transport,
which was mainly dependent on both the independent variables.
Published: February 24, 2006 相似文献
19.
The polyethylene glycol (PEG) treatment of ciprofloxacin-Indion 234 complex was aimed to retard rapid ion exchange drug release
at gastric pH. Ciprofloxacin loading on Indion 234 was performed in a batch process, and the amount of K+ in Indion 234 displaced by drug with time was studied as equilibrium constant KDM. Drug-resin complex (DRC) was treated with aqueous PEG solution (0.5%–2% wt/vol) of different molecular weights (MWs) for
2 to 30 minutes. The PEG-treated ciprofloxacin-Indion 234 complex was evaluated for particle size, water absorption time,
and drug release at gastric pH. During drug loading on Indion 234, the equilibrium constant (KDM) increased rapidly up to 20 minutes with efficient drug loading. Increased time of immersion of the drug resinate in PEG
solutions significantly retained higher size particles upon dehydration. The larger DRC particles showed longer water absorption
times owing to compromised hydrating power. The untreated DRC showed insignificant drug release in deionized water; while
at gastric pH, ciprofloxacin release was complete in 90 minutes. A trend of increased residual particle size, proportionate
increase in water absorption time, and hence the retardation of release with time of immersion was evident in PEG-treated
DRC. The time of immersion of DRC in PEG-treated DRC. The time of immersion of DRC in PEG solution had predominant release
retardant effect, while the effect of molecular weight of PEG was insignificant. Thus, PEG treatment of DRC successfully retards
ciprofloxacin ion exchange release in acidic pH. 相似文献
20.
In this study, the use of biodegradable polymers for microencapsulation of naltrexone using solvent evaporation technique
is investigated. The use of naltrexone microspheres for the preparation of matrix devices is also studied. For this purpose,
poly(L-lactide) (PLA) microspheres containing naltrexone prepared by solvent evaporation technique were compressed at temperatures
above the Tg of the polymer. The effect of different process parameters, such as drug/polymer ratio and stirring rate during
preparation of microspheres, on the morphology, size distribution, and in vitro drug release of microspheres was studied.
As expected, stirring rate influenced particle size distribution of microspheres and hence drug release profiles. By increasing
the stirring speed from 400 to 1200 rpm, the mean diameter of microspheres decreased from 251 μm to 104 μm. The drug release
rate from smaller microspheres was faster than from larger microspheres. However, drug release from microspheres with low
drug content (20% wt/wt) was not affected by the particle size of microspheres. Increasing the drug content of microspheres
from 20% to 50% wt/wt led to significantly faster drug release from microspheres. It was also shown that drug release from
matrix devices prepared by compression of naltrexone microspheres is much slower than that of microspheres. No burst release
was observed with matrix devices. Applying higher compression force, when compressing microspheres to produce tablets, resulted
in lower drug release from matrix devices. The results suggest that by regulating different variables, desired release profiles
of naltrexone can be achieved using a PLA microparticulate system or matrix devices. 相似文献