Several studies have been shown that surfactants are able to increase release rate of drugs from HPMC MATRICES. The present study investigates the effects of various surfactants )nonionic surfactants e.g. Tween 80 with HLB=15 and Arlacel60 with HLB=4.7, sodium lauryl sulphate as an anionic surfactant and cetyl trimethyl ammonium bromide as a cationic surfactant) with different concentrations ranging from 0-10% w/w on the release rate of propranolol hydrochloride from HPMC MATRICES. The results showed that an increase in the concentration of the surfactant with opposite charge to the drug resulted in a reduction in the release rate of propranolol from HPMC MATRICES. It was also found that the surfactant with the same charge as the drug had not considerable effect on the release rate of propranolol. The use of nonionic surfactant with high HLB caused an increase in the release rate of the drug, whereas using the low HLB. surfactant produced a reduction in release rate. The increase in release rate of the drug in presence of surfactant is attributed to an increase in wettability of tablet surfaces, reduction in surface tension, micellar solubilization and increase in drug solubility. The reduction in release rate of the drug could be due to the formation of insoluble complex between the drug of gel layer around matrix and lipophilicity of the matrix surfaces. Studies on the release kinetic of the drug from HPMC MATRICES showed that both diffusion and erosion mechanisms are responsible for the release of propranolol.

Controlled drug release is vital for sustaining the appropriate blood levels. This necessitates a thorough study of drug release profiles. In this study quantitative relationships between chemical structure of drugs and their release from HPMC E4M were investigated using QSPR (Quantitative Structure Property Relationship) technique. To this end, MATRICES containing 100 mg of the polymer and 100 mg of drug were prepared using a constant pressure for 12 drugs from different chemical group and the release profiles were investigated at pH=6.8. Release parameters consisted of drug release rate constants calculated from various kinetic models of zero order, first order, Peppas, Higuchi and Weibull as well as dissolution efficiency, the amount of drug released within the first 8h and the time required for the release of 50% of drugs. Structural parameters were obtained from Molecular mechanics, Quantum mechanics, graph theoretical software packages and ACD log D suit. Stepwise regression analysis was used in Minitab statistical software in order to establish statistically significant relationships between each release parameter and structural descriptors. The resulting equations revealed that increasing the molecular size leads to decreased release rate and efficiency from HPMC E4M MATRICES. However the drug release rate increased with the increase of the drug solubility.

Background and purpose: One of the methods of preparing controlled-release dosage forms is the incorporation of drug in a matrix containing a hydrophilic rate-controlling polymer. Drug-polymer ratio, drug particle size and HPMC particle size have been identified as modifiers of drug release. This study evaluated the relationship and influence of formulation factors such as drug-HPMC ratio and particle size of drug and HPMC on drug release from MATRICES containing HPMC K 15 M and thophylline as model drug.Materials and methods: Theopylline tablets were obtained by the direct compression method using different particle sizes and ratio of theophylline and HPMC K15M. The physicochemical properties of prepared tablets were investigated. Drug release rate was also studied using USP I dissolution apparatus at pH 1.2 and 7.2. From different formulations the theopylline release was analyzed and then the data was fitted to Kinetic models.Results: The results of the present study showed that the rates of theophylline release from HPMC K15 M MATRICES are mainly controlled by the drug-HPMC ratio. The drug and HPMC particle size also influenced the drug release parameters, although to a lesser extent.Conclusion: The main factor influencing the drug release from formulations is the polymer content. There is direct relationship between the polymer particle size and drug release. However, there is an inverse relationship between the drug particle size and release of theophylline.

Hydrophilic and Hydrophobic polymers are widely used excipients to control the release of active ingredients from MATRICES. In this research the effect of various parameter (Type of polymers and their concentrations). On the release rate of atenolol were investigated. Four polymers namely Eudragit RSPO, HPMC K4M NaCMC and EC were used. The results showed that an increase in the Concentration of HPMC and EC in the MATRICES resulted in a reduetion in the release rate of atenolol. As the amount of Eudragit was increased in HPMC MATRICES the release rate of atenolol was not significantly changed (HPMC: Eudragit 3:1). When the ratio of HPMC: Eudragit was 1:1 the release rate of atenolol Significantly increased. The results showed that the release rate of atenolol from NaCMC MATRICES is similar to HPMC MATRICES at pH 1.2, but the release rate at pH 6.8 significantly increased. It can be concluded that the type and concentration of polymers are able to control the release rate of atenolol from MATRICES formulations.

Background and purpose of the study: Propranolol HCl, a widely used drug in the treatment of cardiac arrhythmias and hypertension, is a weak basic drug with pH-dependent solubility that may show release problems from sustained release dosage forms at higher pH of small intestine. This might decrease drug bioavailability and cause variable oral absorption. Preparation of a sustained release matrix system with a pH–independent release profile was the aim of the present study. Methods: Three types of organic acids namely tartaric, citric and fumaric acid in the concentrations of 5, 10 and 15% were added to the MATRICES prepared by hydroxypropyl methylcellulose (HPMC) and dicalcium phosphate. The drug release studies were carried out at pH 1.2 and pH 6.8 separately and mean dissolution time (MDT) as well as similarity factor (ƒ2) were calculated for all formulations. Results and discussion: It was found that incorporation of 5 and 10 % tartaric acid in tablet formulations with 30% HPMC resulted in a suitable pH-independent release profiles with significant higher ƒ2 values (89.9 and 87.6 respectively) compared to acid free tablet (58.03). The other two acids did not show the desirable effects. It seems that lower pKa of tartaric acid accompanied by its higher solubility were the main factors in the achievement of pH-independent release profiles.

In this study, the effects of various hydrophilic (HPMC and Carbopol 971) and plastic (Ethylcellulose and Eudragit RL100) polymers on the release profile of diltiazem HCl from matrix tablets were evaluated in-vitro. For this purpose, tablets containing 60 mg of diltiazem HCl along with various amounts of the aforementioned polymers were prepared using the wet granulation technique. Tablets prepared were placed in a USP apparatus I dissolution tester containing a pH-1.5 HCl solution for the first 2 h and a pH-6.8 phosphate buffer for the next 10 h of the study. The amount of drug released was determined at 237 nm by a UV-visible spectrophotometer. The results showed that all the polymers used in this study could slow down the release of diltiazem HCl from the MATRICES prepared. This effect, except for HPMC, generally increased proportionately with the amount of polymer. HPMC imparted the best control over drug release and could sustain it for approximately 6 h. All the MATRICES prepared had a burst release initially; however, it was minimum with HPMC-containing formulations. Fitting of release data to different kinetic models showed that HPMC-MATRICES conformed best to Hixson-Crowell model, ethylcellulose-MATRICES to Higuchi and both Eudragit RL100 and Carbopol 971-formulations to either of Hixson-Crowell, Higuchi and first-order kinetics. Release exponent (n) derived from Korsmeyer-Peppas equation for the studied formulations implied that the release of diltiazem HCl from HPMC-MATRICES was non-Fickian (0.62-0.66) and that of ethylcellulose-formulations was Fickian (n~0.4). The values of n for Eudragit RL100 and Carbopol 971-MATRICES ranged from 0.46-0.59, indicating that the drug release was mainly governed by diffusion. Briefly, HPMC was found to be suitable for sustaining the release of diltiazem HCl from matrix-type tablets. Nevertheless, to achieve better results with this polymer, further investigations seem to be necessary.

In this paper, a class of MATRICES, namely, Drazin-dagger MATRICES, in which the Drazin inverse andthe Moore-Penrose inverse commute, is introduced. Also, some properties of the generalized inverses of these MATRICES, are investigated. Moreover, some results about the Moore-Penrose inverse, the Drazin inverse and the numerical range of some reciprocal MATRICES are obtained. In particular, the relations between reciprocal MATRICES, Drazin-Dagger MATRICES and star order are established. Also, some properties of the generalized inverses of the conjugate EP MATRICES are studied. To illustrate the results, some numerical examples are also given.

Please click on PDF to view the abstract

Captopril is an angiotension-converting enzyme inhibitor used in the treatment of hypertension. It is freellly water soluble and has an elimination half-life after oral dose of 1.7 h. Various methods are available to formulate water soluble drugs into sustained release dosage forms by retarding the dissolution rate. One of the methods used to control drug release and hence, prologn therapeutic activity is to use hydrophilic and lipophilic polymers. In this study the effects of various polymers (hydroxyprpylemethylcellulose,) ethyl cellulose and sodium carboxymethylcellulose) and surfactants (sodium lauryl sulphate, ceytltriammonium bromide and arlacel 60) on the release rate of captopril were investigated. The results showed that an increase in the amount of HPMC KI5M resulted in a reduction in the release rate of captopril from MATRICES. When the HPMC was partly replaced by NaCMC (the ratio of HPMC: NaCMC was 5:1) the release rate of the drug significantly decreased. However, there was no significant difference in release rate of captopril from MATRICES produced with the ratios of 5:1 and 2:1 of HPMC:NaCMC. The presence of lactose in MATRICES containing HPMC and NaCMC increased the release rate of captopril. It was interesting that although partial replacement of HPMC by EC reduced the release rate of the drug (ratio of HPMC: EC was 2:1), when the ratio of HPMC:EC was reduced to 1:1 the release rate was increased. The effects of various surfactants on the release rate of captopril from HPMC: EC (1:1) MATRICES was also investigated. The results showed that the surfactants did not significantly change the release rate of the drug. Release rate of the drug. Release data were examined kinetically and the ideal kinetic models were estimated for the drug release.

An improved topical gel was developed which could allow fast release of drug and having appropriate organoleptic (texture) and rheological properties (viscosity). In vitro release of diclofenac potassium from hydrophobically modified hydroxypropyl methyl cellulose (hm-HPMC, 90L grade) based gels (F1, F2 and F3 at 1, 1.5 and 2 % (w/v) concentration, respectively) was compared with conventional hydrophilic hydroxypropyl methylcellulose (HPMC, 50 mPa s) based gels (F4 and F5 at 12 and 15 % (w/v) concentration, respectively). This study was performed in Franz diffusion cell using cellulose dialysis membrane. The hm-HPMC-based gels of higher viscosity release remarkable quantity of the drug in comparison to conventional hydrophilic HPMC-based gels of lower viscosity. So in the drug-release process polymer concentration is more important and a determinant factor compared to viscosity. Texture profile and viscosity of hm-HPMC-based gels were compared with a commercial gel and all the rheological data obtained from the experiments confirm the suitability of these hm-HPMC-based gels for use as a topical drug delivery system. In order to achieve percutaneous penetration of drug, permeation enhancers (n-octanol and propylene glycol) were added in hm-HPMC-based gels. Both enhancers have shown enhancement of drug penetration through rat skin. Propylene glycol at both lower concentration (2 %) and higher concentration (5 %) exhibited a greater increase in the permeation flux as well as more antinociceptive activity than formulations without enhancer or with n-octanol as enhancer.