Kofi Asare-Addo

The Role of Oral Controlled Release Matrix Tablets in Drug Delivery Systems

Formulations that are able to control the release of drug have become an integral part of the pharmaceutical industry. In particular oral drug delivery has been the focus of pharmaceutical research for many years. This type of drug delivery has been at the centre of research due to its many benefits over conventional dosage. The focus of this review is on matrix tablets due to their widely use and simplicity of the formulation. This includes the discussion of various types of matrix tablets and factors affecting the drug release from these formulations. The mechanism of drug release from HPMC matrices is also discussed.

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices.

The evaluation of the effects of different media ionic strengths and pH on the release of hydrochlorothiazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix was the objective of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the ionic strength had a profound effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength. For example, drug release after the 1h mark for the K100M matrices in water was 36%. Drug release in pH 1.2 after 1h was 30%. An increase of the pH 1.2 ionic strength to 0.4M saw a reduction of drug release to 26%. This was the general trend for the K4M and K15M matrices as well. The similarity factor f2 was calculated using drug release in water as a reference. Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2=64-72), increases of ionic strength at 0.2M and 0.4M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2=56-81). The values of f2 however reduced with increasing ionic strengths. DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices. There was an increase in bound water as ionic strengths increased. Texture analysis was employed to determine the gel strength and also to explain the drug release for the diltiazem hydrochloride. This methodology can be used as a valuable tool for predicting potential ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices.

The influence of agitation sequence and ionic strength on in vitro drug release from hypromellose (E4M and K4M) ER matrices--the use of the USP III apparatus.

Theophylline extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC) E4M and K4M were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The objectives of this study were to evaluate the effects of systematic agitation, ionic strength and pH on the release of theophylline from the gel forming hydrophilic polymeric matrices with different methoxyl substitution levels. Tribo-electric charging of hypromellose, theophylline and their formulated blends containing E4M and K4M grades has been characterised, along with quantitative observations of flow, compression behaviour and particle morphology. Agitations were studied at 5, 10, 15, 20, 25, 30 dips per minute (dpm) and also in the ascending and descending order in the dissolution vials. The ionic concentration strength of the media was also varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. To study the effect of ionic strength on the hydrophilic matrices, agitation was set at 20 dpm. The charge results on individual components imply that the positively charged particles have coupled with the negatively charged particles to form a stable ordered mixture which is believed to result in a more homogeneous and stable system. The particle shape analysis showed the HPMC K4M polymer to have a more irregular morphology and a rougher surface texture in comparison to the HPMC E4M polymer, possibly a contributory factor to the gelation process. The results showed gelation occurred quicker for the K4M tablet matrices. Drug release increased with increased agitation. This was more pronounced for the E4M tablet matrices. The ionic strength also had more of an effect on the drug release from the E4M matrices. The experiments highlighted the resilience of the K4M matrices in comparison with the E4M matrices. The results thus show that despite similar viscosities of E4M and K4M, the methoxyl substitution makes a difference to their control of drug release and as such care and consideration should be given to the choice of polymer used for extended release. The use of systematic change of agitation method and ionic strength may indicate potential fed and fasted effects on drug release from hydrophilic matrices.

Study of dissolution hydrodynamic conditions versus drug release from hypromellose matrices: the influence of agitation sequence.

In this article, the influence of agitation in descending and ascending sequences as a systematic method development process for potentially discriminating fed and fasted states and evaluation of its effects on the drug release from swelling gel-forming hydrophilic matrix tablets were investigated. Theophylline extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus at 5, 10, 15, 20, 25 and 30 dips per minute (dpm). Agitation had a profound effect on the drug release from the HPMC K100LV matrices. Drug release in pH 1.2 changed from about 40% at 5 dpm to about 80% at 30 dpm over a 60 min period alone. The matrices containing HPMC K4M, K15M and K100M however were not significantly affected by the agitation rate. The similarity factor f2 was calculated using drug release at 10 dpm as a reference. The ascending agitations of 5-30 dpm and the descending order of agitation 30-5 dpm were also evaluated. Anomalous transport was the only kinetic of release for the K4M, K15M and K100M tablet matrices. The lower viscous polymer of K100LV had some matrices exhibiting Fickian diffusion as its kinetics of release. The use of systematic change of agitation method may indicate potential fed and fasted effects on drug release from hydrophilic matrices.

Psyllium: a promising polymer for sustained release formulations in combination with HPMC polymers.

Abstract Psyllium has a mucilaginous property that makes it a good candidate to be utilized as an excipient in the preparation of controlled release systems. Various formulations were prepared using theophylline as a model drug and investigated with a view to achieve an ideal slow drug release profile. The addition of hydroxypropyl methylcellulose (HPMC) to psyllium significantly reduced the burst release; however, the percentage of drug release within a 12 h period was too slow and thereby inadequate. This was overcome by the addition of lactose as a hydrophilic filler that enabled a slow release with roughly 80% drug release in 12 h. The inclusion of HPMC within psyllium formulations changed the drug release kinetics from Fickian diffusion to anomalous transport. Granulated formulations demonstrated slower drug release than ungranulated or physical mixture and caused a change in the dissolution kinetics from Fickian diffusion to anomalous transport. Milled granules showed more efficient controlled drug release with no burst release. Milling of the granules also changed the drug release kinetics to anomalous transport. Although psyllium was proved to be a promising polymer to control the drug release, a combination of psyllium-HPMC and formulation processes should be considered in an attempt to achieve a zero-order release.

Effect of glucosamine HCl on dissolution and solid state behaviours of piroxicam upon milling

Piroxicam is a non-steroidal anti-inflammatory drug that is characterised by low solubility and high permeability. In order to improve the drug dissolution rate, the co-grinding method was used as an approach to prepare piroxicam co-ground in the carriers such as glucosamine hydrochloride. As, this amino sugar (glucosamine HCl) has been shown to decrease pain and improve mobility in osteoarthritis in joints, therefore, the incorporation of glucosamine in piroxicam formulations would be expected to offer additional benefits to patients. The effect of the order of grinding on the dissolution of piroxicam was also investigated. Co-ground drug and glucosamine were prepared in different ratios using a ball mill. The samples were then subjected to different grinding times. In order to investigate the effect of the grinding process on the dissolution behaviour of piroxicam, the drug was ground separately in the absence of glucosamine. Mixtures of ground piroxicam and unground D-glucosamine HCl were prepared. Physical mixtures of piroxicam and glucosamine were also prepared for comparison. The properties of prepared co-ground systems and physical mixtures were studied using a dissolution tester, FTIR, SEM, XRPD and DSC. These results showed that the presence of glucosamine HCl can increase dissolution rate of piroxicam compared to pure piroxicam. Generally, all dissolution profiles showed the fastest dissolution rate when ground piroxicam was mixed with unground glucosamine. This was closely followed by the co-grinding of piroxicam with glucosamine where lower grinding times showed the fastest dissolution. The solid state studies showed that the grinding of piroxicam for longer times had no effect on polymorphic form of piroxicam, whereas mixtures of piroxicam-glucosamine ground for longer times (60 min) converted piroxicam polymorph II to polymorph I.

Drug release from matrix tablets: physiological parameters and the effect of food

Introduction: As dissolution plays an important and vital role in the drug-delivery process of oral solid dosage forms, it is, therefore, essential to critically evaluate the parameters that can affect this process. Areas covered: The consumption of food as well as the physiological environment and properties of the gastrointestinal tract, such as its volume and composition of fluid, the fluid hydrodynamics, properties of the intestinal membrane, drug dose and solubility, pKa, diffusion coefficient, permeability and particle size, all affect drug dissolution and absorption rate. There are several dissolution approaches that have been developed to address the conditions as experienced in the in vivo environment, as the traditional dissolution being a quality control method is not biorelevant and as such do not always produce meaningful data. This review also describes the development of a systematic way that differentiates between robust and non-robust formulations by varying the effects of agitation and ionic strength through the use of the automated United States Pharmacopeia type III Bio-Dis apparatus. Expert opinion: With the improved understanding of the physiological parameters that can affect the oral bioperformance of dosage forms, strides have, therefore, been made in making dissolution testing methods more biologically based with the view of obtaining more in vitro–in vivo correlations.

Triboelectrification and dissolution property enhancements of solid dispersions

The use of solid dispersion techniques to modify physicochemical properties and improve solubility and dissolution rate may result in alteration to electrostatic properties of particles. Particle triboelectrification plays an important part in powder processing, affecting end product quality due to particle deposition and powder loss. This study investigates the use of glucosamine hydrochloride (GLU) in solid dispersions with indomethacin. Solvents selected for the preparation of the dispersions were acetone, acetone-water, ethanol and ethanol-water. Solid state characterizations (DSC, FTIR and XRPD) and dissolution were conducted. Dispersions were subjected to charge using a custom built device based on a shaking concept, consisting of a Faraday cup connected to an electrometer. All dispersions improved the dissolution rate of indomethacin. Analysis showed the method of preparation of the dispersion induced polymorphic forms of the drug. Indomethacin had a high propensity for charging (-411 nC/g). GLU had a very low charge (-1 nC/g). All dispersions had low charges (-1 to 14 nC/g). Acetone as a solvent, or in combination with water, produced samples with an electronegative charge in polarity. The same approach with ethanol produced electropositive charging. The results show the selection of solvents can influence powder charge thereby improving powder handling as well as dissolution properties.

The design of naproxen solid lipid nanoparticles to target skin layers.

The aim of the current investigation was to produce naproxen solid lipid nanoparticles (Nap-SLNs) by the ultrasonication method to improve its skin permeation and also to investigate the influence of Hydrophilic-lipophilic balance (HLB) changes on nanoparticles properties. The properties of obtained SLNs loaded with naproxen were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). FT-IR was also used to investigate any interaction between naproxen and the excipients used at the molecular level during the preparation of the SLNs. The performance of the formulations was investigated in terms of skin permeation and also the retention of the drug by the skin. It was found that generally, with increasing the lipid concentration, the average particle size and polydispersity index (PDI) of SLNs increased from 94.257±4.852nm to 143.90±2.685nm and from 0.293±0.037 to 0.525±0.038 respectively. The results also showed that a reduction in the HLB resulted in an increase in the PDI, particle size, zeta potential and entrapment efficiency (EE%). DSC showed that the naproxen encapsulated in the SLNs was in its amorphous form. The peaks of prominent functional groups of naproxen were found in the FT-IR spectra of naproxen-SLN, which confirmed the entrapment of naproxen in the lipid matrix. FT-IR results also ruled out any chemical interaction between drug and the chemicals used in the preparation of SLNs. The amount of naproxen detected in the receptor chamber at all the sampling times for the reference formulation (naproxen solution containing all surfactants at pH 7.4) was higher than that of the Nap-SLN8 formulation. Nap-SLN8 showed an increase in the concentration of naproxen in the skin layer with less systemic absorption. This indicates that most of the drug in Nap-SLN8 remains in the skin which can reduce the side effect of systemic absorption of the drug and increases the concentration of the drug at the site of the action.

Starch-free grewia gum matrices: Compaction, swelling, erosion and drug release behaviour

Polysaccharides are suitable for application as hydrophilic matrices because of their ability to hydrate and swell upon contact with fluids, forming a gel layer which controls drug release. When extracted from plants, polysaccharides often contain significant quantities of starch that impacts upon their functional properties. This study aimed to evaluate differences in swelling, erosion and drug release from matrix tablets prepared from grewia gum (GG) and starch-free grewia gum (GDS) extracted from the stems of Grewia mollis. HPMC was used as a control polymer with theophylline as a model drug. Swelling, erosion, and in-vitro release were performed in deionized water, pH 1.2 and pH 6.8 media. The Vergnaud and Krosmeyer-Peppas model were used for swelling and drug release kinetics, respectively. However, linear regression technique was used to determine the erosion rate. GDS compacts were significantly harder than the native GG and HPMC compacts. GDS matrices exhibited the fastest erosion and drug release in deionised water and phosphate buffer compared with the GG and HPMC. At pH 1.2, GDS exhibited greater swelling than erosion, and drug release was similar to GG and HPMC. This highlights the potential of GDS as a matrix for controlled release similar to HPMC and GG at pH 1.2 but with a more rapid release at pH 6.8. GDS may have wider application in reinforcing compacts with relatively low mechanical strength.