An investigation of physicochemical properties of piroxicam liquisolid compacts

The potential of liquisolid systems to improve the dissolution properties of a water-insoluble agent (piroxicam) was investigated. In this study, physicochemical properties of piroxicam liquisolid tablets, effect of aging, and type of the carrier were also investigated. To this end, several liquisolid tablets formulations containing various ratios of drug: solvent and different carriers were prepared. X-ray crystallography, differential scanning calorimetry (DSC), and contact angle measurement were used for evaluation of physicochemical properties of piroxicam. Liquisolid compacts exhibited significantly higher drug dissolution rates, in different dissolution media, than compacts prepared by the direct compression technique. The results showed that enhanced dissolution rate of piroxicam liquisolid tablets was due to an increase in wetting properties and surface area of drug available for dissolution. To investigate the effect of aging on the hardness and dissolution rate of liquisolid compacts, the formulations were stored at 25 degrees C/75% relative humidity for 9 months. The results showed that aging had no significant effect on hardness or dissolution profile of liquisolid tablets. It was shown that Avicel had more liquid retention potential than other carriers, but there were no significant differences in the dissolution profiles between formulations. The results of DSC and X-ray crystallography did not show any changes in crystallinity of the drug and interaction between piroxicam and exipients (Avicel and silica) during the process.     

Liquisolid systems to improve the dissolution of furosemide

A liquisolid system has the ability to improve the dissolution properties of poorly water soluble drugs. Liquisolid compacts are flowing and compactable powdered forms of liquid medications. The aim of this study was to enhance the in vitro dissolution properties of the practically water insoluble loop diuretic furosemide, by utilising liquisolid technique. Several liquisolid tablets were prepared using microcrystalline cellulose (Avicel® pH-101) and fumed silica (Cab-O-Sil® M-5) as the carrier and coating materials, respectively. Polyoxy-ethylene-polyoxypropylene-polyoxyethylene block copolymer (Synperonic® PE/L 81); 1,2,3-propanetriol, homopolymer, (9Z)-9-octadecenoate (Caprol® PGE-860) and polyethylene glycol 400 (PEG 400) were used as non- volatile water-miscible liquid vehicles. The liquid loading factors for such liquid vehicles were calculated to obtain the optimum amounts of carrier and coating materials necessary to produce acceptable flowing and compactible powder admixtures viable to produce compacts. The ratio of carrier to coating material was kept constant in all formulations at 20 to 1. The formulated liquisolid tablets were evaluated for post compaction parameters such as weight variation, hardness, drug content uniformity, percentage friability and disintegration time. The in-vitro release characteristics of the drug from tablets formulated by direct compression (as reference) and liquisolid technique, were studied in two different dissolution media. Differential scanning calorimetry (DSC) and Fourier-Transform infrared spectroscopy (FT-IR) were performed. The results showed that all formulations exhibited higher percentage of drug dissolved in water (pH 6.4–6.6) compared to that at acidic medium (pH 1.2). Liquisolid compacts containing Synperonic® PE/L 81 demonstrated higher release rate at the different pH values. Formulations with PEG 400 displayed lower drug release rate, compared to conventional and liquisolid tablets. DSC and FT-IR indicated a possible interaction between furosemide and tablet excipients that could explain the dissolution results. Caprol® PGE-860, as a liquid vehicle, failed to produce furosemide liquisolid compacts.     

Liquisolid Tablets for Dissolution Enhancement of a Hypolipidemic Drug

This investigation was aimed to improve the dissolution rate of the poorly soluble drug lovastatin, by formulating it as a liquisolid compact. Different liquisolid compacts were prepared using mathematical formulae to calculate the required quantities of powder and liquid ingredients to produce acceptably flowable and compressible admixture. Avicel PH 200, Cab-O-Sil, sodium starch glycolate and PEG 400 were employed as carrier, coating material, disintegrant and non-volatile liquid vehicle, respectively. The various drug to liquid and carrier to coating ratio were used to prepare liquisolid compacts. The formulated liquisolid tablets were evaluated for weight variation, hardness, drug content, friability and disintegration time. The in vitro release characteristics of the drug from tablets formulated by direct compression and liquisolid technique were compared in two different dissolution media. The tableting properties of the liquisolid compacts were within the acceptable limits and drug release rates were distinctly higher as compared to directly compressed tablets. The FTIR spectra showed no interaction between drug-excipient and disappearance of the characteristic absorption band of lovastatin in liquisolid formulations could be attributed to the formation of hydrogen bonding between the drug and liquid vehicle, which resulted in dissolution enhancement. Thus, the liquisolid technique was found to be a promising approach for improving the dissolution of a poorly soluble drug like lovastatin.     

Enhancement of griseofulvin release from liquisolid compacts

The potential of hydrophilic aerogel formulations and liquisolid systems to improve the release of poorly soluble drugs was investigated using griseofulvin as model drug. The in vitro release rates of this drug formulated as directly compressed tablets containing crystalline griseofulvin were compared to aerogel tablets with the drug adsorbed onto hydrophilic silica aerogel and to liquisolid compacts containing the drug dissolved or suspended in PEG 300. Furthermore, the commonly used carrier and coating materials in liquisolid systems Avicel® and Aerosil® were replaced by Neusilin®, an amorphous magnesium aluminometasilicate with an extremely high specific surface area of 339 m²/g to improve the liquisolid approach.Both the liquisolid compacts containing the drug dissolved in PEG 300 and the aerogel tablets showed a considerably faster drug release than the directly compressed tablets. With liquisolid compacts containing the drug suspended in PEG 300, the release rate increased with rising fraction of dissolved drug in the liquid portion. It could be shown that Neusilin® with its sevenfold higher liquid adsorption capacity than the commonly used Avicel® and Aerosil® allows the production of liquisolid formulations with lower tablet weights.     

Formulation and evaluation of liquisolid compacts of diclofenac sodium

The technique of liquisolid compacts is a promising method towards enhancing the dissolution of poorly soluble drugs. In the present study, the potential of liquisolid systems to improve the dissolution properties of water-insoluble agents was investigated using diclofenac sodium as the model drug. Several formulations of liquisolid compacts having different drug concentration (30% to 50% w/w) and with varying ratios of carrier to coat (i.e., different R values, ranging from 5 to 50) were prepared. Avicel and Aerosil were used as carrier and coat material, respectively, and propylene glycol was used as a nonvolatile liquid to prepare liquid medication. The effect of added liquid on the flowability and compressibility of the final admixture was studied and the effect of drug concentration on the dissolution pattern of diclofenac sodium was investigated. Liquisolid compacts demonstrated significantly higher drug release rates than the pure drug.     

Effects of liquisolid formulations on dissolution of naproxen

The aim of this study was to investigate the use of liquisolid technique in improving the dissolution profiles of naproxen in a solid dosage form. This study was designed to evaluate the effects of different formulation variables, i.e. type of non-volatile liquid vehicles and drug concentrations, on drug dissolution rates. The liquisolid tablets were formulated with three different liquid vehicles, namely Cremophor^® EL (polyoxyl 35 castor oil), Synperonic^® PE/L61 (poloxamer 181, polyoxyethylene-polyoxypropylene copolymer) and poly ethylene glycol 400 (PEG400) at two drug concentrations, 20%w/w and 40%w/w. Avicel^® PH102 was used as a carrier material, Cab-o-sil^® M-5 as a coating material and maize starch as a disintegrant. The empirical method as introduced by Spireas and Bolton (1999) [1] was applied strictly to calculate the amounts of coating and carrier materials required to prepare naproxen liquisolid tablets. Quality control tests, i.e. uniformity of tablet weight, uniformity of drug content, tablet hardness, friability test, disintegration and dissolution tests were performed to evaluate each batch of prepared tablets. In vitro drug dissolution profiles of the liquisolid formulations were studied and compared with conventional formulation, in simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 7.2) without enzyme. Stability studies were carried out to evaluate the stability of the tablets under humid conditions. Differential scanning calorimetry and Fourier transform infrared were used to investigate physicochemical interaction between naproxen and the excipients. It was found that liquisolid tablets formulated with Cremophor^® EL at drug concentration of 20%w/w produced high dissolution profile with acceptable tablet properties. The stability studies showed that the dissolution profiles of liquisolid tablets prepared with Cremophor^® EL were not affected by ageing significantly. Furthermore, DSC revealed that drug particles in liquisolid formulations were completely solubilised.     

Formulation factors affecting the release of ezetimibe from different liquisolid compacts

Context: Liquisolid technique is one of the methods used to improve the dissolution rate of the poorly water soluble drugs utilizing non volatile liquids.Objectives: Enhancement of the release of ezetimibe from different liquisolid formulations.Materials and Methods: Four liquid vehicles were used to prepare the liquid medications with different drug concentrations. The interaction between the drug and the excipients in liquisolid powders were characterized by DSC, X-ray, FTIR and SEM. Furthermore, the powder characteristics were evaluated by Carr’s Index and powder wetting time determinations, respectively. All prepared formulations were compressed at different pressures to end with the same constant porosity and the tablets were evaluated by different tests and compared with conventional formula. Results and Discussion: No interaction had been detected in all liquisolid formulations as shown in the results of XRD, FTIR, DSC and SEM. In addition to that, all liquisolid compacts had expressed faster dissolution profiles compared with that of conventional formula. Conclusion: The dissolution rate was affected by the drug concentration, solubility of the drug in the liquid vehicle and type of carrier. In addition, the presence of the liquid vehicle has been found to affect the mechanical properties of the liquisolid formulations.     

Liquisolid technique for dissolution rate enhancement of a high dose water-insoluble drug (carbamazepine)

Different liquisolid formulations of carbamazepine were accomplished by dissolving the drug in the non-toxic hydrophilic liquids, and adsorbing the solution onto the surface of silica. In order to reduce the amounts of carrier and aerosil in liquisolid formulations, some additives namely polyvinylpyrrolidone (PVP), hydroxypropyle methylcellulose (HPMC) and polyethylene glycol (PEG 35000) were added to liquid medication to increase loading factor. The effects of various ratios of carrier to coating material, PVP concentration, effect of aging and type of the carrier on dissolution rate of liquisolid compacts were studied. X-ray crystallography and differential scanning calorimetery (DSC) were used for evaluation of physicochemical properties of carbamazepine in liquisolid formulations. The results showed that the drug loading factor was increased significantly in the presence of additives. Liquisolid formulations containing PVP as additive, exhibited significantly higher drug dissolution rates compared to the compacts prepared by the direct compression technique. It was shown that microcrystalline cellulose had more liquid retention potential in comparison with lactose, and the formulations containing microcrystalline cellulose as carrier, showed higher dissolution rate. By decreasing the ratio of microcrystalline cellulose to silica from 20 to 10, an improvement in dissolution rate was observed. Further decrease in the ratio of microcrystalline cellulose:silica from 10 to 5 resulted in a significant reduction in dissolution rate. Increasing of PVP concentration in liquid medication caused a dramatic increase in dissolution rate at first 30min. The results showed that the dissolution rate of liquisolid tablets was not significantly affected by storing the tablets at 25 degrees C/75% relative humidity for a period of 6 months. The results of DSC and X-ray crystallography did not show any changes in crystallinity of the drug and interaction between carbamazepine and exipients during the process.     

Use of the liquisolid compact technique for improvement of the dissolution rate of valsartan

The aim of this study was to improve the dissolution rate of the poorly soluble drug valsartan by delivering the drug as a liquisolid compact. Liquisolid compacts were prepared using propylene glycol as solvent, Avicel PH102 as carrier, and Aerosil 200 as the coating material. The crystallinity of the newly formulated drug and the interaction between excipients was examined by X-ray powder diffraction and Fourier-transform infrared spectroscopy, respectively. The dissolution studies for the liquisolid formulation and the marketed product were carried out at different pH values. The results showed no change in the crystallinity of the drug and no interaction between excipients. The dissolution efficiency of valsartan at 15 min was increased from 4.02% for plain drug and 13.58% for marketed product to 29.47% for the liquisolid formulation. The increase in the dissolution rate was also found to be significant compared to the marketed product at lower pH values, simulating the gastric environment where valsartan is largely absorbed. The liquisolid technique appears to be a promising approach for improving the dissolution of poorly soluble drugs like valsartan.     

Liquisolid technique to enhance and to sustain griseofulvin dissolution: effect of choice of non-volatile liquid vehicles

Liquisolid systems were originally designed to enhance dissolution of hydrophobic drugs. Recently, the same technique was explored to control drug release via hydrophobic carriers. This work aimed to study the effects of different liquid vehicles on release characteristics of griseofulvin as a model hydrophobic drug. Fast dissolution tablets were prepared using three different non-ionic surfactants namely Cremophor(?)EL, Synperonic(?)PE/L61 and Capryol? 90, on the contrary Kollicoat(?)SR 30D was used for production of grieseofulvin sustained release formulations. Avicel(?) PH102 and Cab-O-Sil(?) M5 were used as carrier and coat materials, respectively. The effect of formulation parameters, such as drug concentration and carrier to coat ratio, on enhancing drug dissolution was explored. Drug concentrations of 20% and 40% (w/w), and R-values (carrier to coat ratio) of 10 and 20 were used. The mathematical model was utilized to formulate liquisolid powder systems. All fast release liquisolid formulations showed higher percentage drug dissolution efficiency (%DE) than conventional directly compacted tablets. Cremophor(?)EL showed the best dissolution enhancement with %DE of about 90%, compared to only 23% for conventional tablets; DSC data suggested loss of griseofulvin crystallinity and thermal behavior. Kollicoat(?) SR 30D retarded the drug release even in the presence of hydrophilic carrier; DSC data suggested that only small fraction of the drug was present in the molecular state within the system. The used liquisolid vehicles showed promise to enhance and to control (depend on the choice of the liquid vehicle) the release of griseofulvin from liquisolid compacts.     

Formulation and optimization of liquisolid compact for enhancing dissolution properties of efavirenz by using DoE approach

Efavirenz displays low and variable bioavailability because of its poor aqueous solubility and high log P-value. The present investigation was aimed to improve the dissolution profile of efavirenz by using a simple, scalable and cost-effective technique of liquisolid compact. The drug was dissolved in Trancutol-HP for preparing the liquid medicament which was subsequently mixed with carrier and coating material to make free-flowing and compressible powder. 3² full factorial design was used to optimize the formulation in which the Neusilin US2/Corn starch ratios and carrier/coating material ratio were selected as independent variables. The results of in-vitro dissolution test proved that liquisolid compacts have significantly higher dissolution rate than tablets containing pure drug. Results of DSC and XRD studies suggested that the high dissolution of the drug from the liquisolid compacts was possibly because of the drug either being in an amorphous state or being molecularly dispersed within the internal matrix of compacts.     

Investigation of the effect of solubility increase at the main absorption site on bioavailability of BCS class II drug (risperidone) using liquisolid technique

BCS class II drugs usually suffer inadequate bioavailability as dissolution step is the absorption rate limiting step. In this work, the effect of solubility increase at the main absorption site for these drugs was investigated using risperidone as a drug model. Liquisolid technique was applied to prepare risperidone per-oral tablets of high dissolution rate at intestinal pH (6.8) using versatile nonionic surfactants of high solubilizing ability [Transcutol HP, Labrasol and Labrasol/Labrafil (1:1) mixture] as liquid vehicles at different drug concentrations (10–30%) and fixed (R). The prepared liquisolid tablets were fully evaluated and the dissolution rate at pH 6.8 was investigated. The formulae that showed significantly different release rate were selected and subjected to mathematical modeling using DE₂₅, MDT and similarity factor (f2). Depending on mathematical modeling results, formula of higher dissolution rate was subjected to solid state characterization using differential scanning calorimetric (DSC), infrared spectroscopy (IR) and X-ray diffraction (XRD). Finally, the drug bioavailability was studied in comparison to conventional tablets in rabbits. Results showed that liquisolid tablet prepared using Labrasol/Labrafil (1:1) mixture as liquid vehicle containing 10% risperidone is a compatible formula with law drug crystallinity and higher dissolution rate (100% in 25?min). The drug bioavailability was significantly increased in comparison to the conventional tablets (1441.711?μg h/mL and 137.518?μg/mL in comparison to 321.011?μg h/mL and 38.673?μg/mL for AUC and Cp_max, respectively). This led to the conclusion that liquisolid technique was efficiently improved drug solubility and solubility increase of BCS class II drugs at their main absorption site significantly increases their bioavailability.     

Drug release from liquisolid systems: speed it up, slow it down

INTRODUCTION: Today, the properties of many new chemical entities have shifted towards higher molecular weights and this in turn increases the lipophilicity hence decreasing aqueous solubility. The low solubility of drugs usually has in vivo consequences such as low bioavailability, increased chance of food effect and incomplete release from the dosage form. AREAS COVERED: The present review discusses the advantages of the liquisolid technology in formulation design of poorly water soluble drugs for dissolution enhancement and highly water soluble drugs for slow release pattern. EXPERT OPINION: With the advent of high throughput screening and combinatorial chemistry, it has been shown that most of the new chemical entities have a high lipophilicity and poor aqueous solubility, hence poor bioavailability. In order to improve the bioavailability, the release rate of these drugs should be enhanced. Although there are multiple technologies to tackle this issue, they are not cost effective due to the involvement of sophisticated machinery, advanced preparation techniques and complicated technology. As the liquisolid technology uses a similar production process as the conventional tablets, this technology to improve the release rate of poorly water soluble drugs will be cost effective. This technology also has the capability to slow down drug release and allows preparing sustained release tablets with zero order drug release pattern. The excipients required for this technology are conventional and commonly available in the market. The technology is in the early stages of its development with extensive research currently focused on. It is envisaged that the liquisolid compacts could play a major role in the next generation of tablets.     

Drug release from liquisolid systems: speed it up,slow it down

Introduction: Today, the properties of many new chemical entities have shifted towards higher molecular weights and this in turn increases the lipophilicity hence decreasing aqueous solubility. The low solubility of drugs usually has in vivo consequences such as low bioavailability, increased chance of food effect and incomplete release from the dosage form.

Areas covered: The present review discusses the advantages of the liquisolid technology in formulation design of poorly water soluble drugs for dissolution enhancement and highly water soluble drugs for slow release pattern.

Expert opinion: With the advent of high throughput screening and combinatorial chemistry, it has been shown that most of the new chemical entities have a high lipophilicity and poor aqueous solubility, hence poor bioavailability. In order to improve the bioavailability, the release rate of these drugs should be enhanced. Although there are multiple technologies to tackle this issue, they are not cost effective due to the involvement of sophisticated machinery, advanced preparation techniques and complicated technology. As the liquisolid technology uses a similar production process as the conventional tablets, this technology to improve the release rate of poorly water soluble drugs will be cost effective. This technology also has the capability to slow down drug release and allows preparing sustained release tablets with zero order drug release pattern. The excipients required for this technology are conventional and commonly available in the market. The technology is in the early stages of its development with extensive research currently focused on. It is envisaged that the liquisolid compacts could play a major role in the next generation of tablets.     

Use of biorelevant media for assessment of a poorly soluble weakly basic drug in the form of liquisolid compacts: in vitro and in vivo study

The purpose of this work is to use biorelevant media to evaluate the robustness of a poorly water soluble weakly basic drug to variations along the gastrointestinal tract (GIT) after incorporation in liquisolid compacts and to assess the success of these models in predicting the in vivo performance. Liquisolid tablets were prepared using mosapride citrate as a model drug. A factorial design experiment was used to study the effect of three factors, namely: drug concentration at two levels (5% and 10%), carriers at three levels (avicel, mannitol and lactose) and powder excipients ratio (R) of the coating material at two levels (25 and 30). The in vitro dissolution media utilized were 0.1?N HCl, hypoacidic stomach model and a transfer model simulating the transfer from the stomach to the intestine. All compacts released above 95% of drug after 10?min in 0.1?N HCl. In the hypoacidic model, the compacts with R 30 were superior compared to R 25, where they released >90% of drug after 10?min compared to 80% for R 25. After the transfer of the optimum compacts from Simulated gastric fluid fast (SGFfast) to fasted state simulated intestinal fluid, slight turbidity appeared after 30?min, and the amount of drug dissolved slightly decreased from 96.91% to 90.59%. However, after the transfer from SGFfast to fed state simulated intestinal fluid, no turbidity or precipitation occurred throughout time of the test (60?min). In vivo pharmacokinetic study in human volunteers proved the success of the in vitro models with enhancement of the oral bioavailability (121.20%) compared to the commercial product.     

Development and in vitro evaluation of an enteric-coated multiparticulate drug delivery system for the administration of piroxicam to dogs.

The aim of the study was to develop enteric-coated pellets for the administration of piroxicam (a poorly water-soluble drug) to small animals in order to avoid local gastrointestinal irritation, one of the major side effects of nonsteroidal anti-inflammatory drugs after oral ingestion. Pellets were made by an extrusion-spheronization process. The influence of several excipients on the in vitro drug release was evaluated. Piroxicam release from the uncoated pellets was measured in phosphate buffer (pH 6.8) using the paddle dissolution method (USP XXIII). The enteric-coated pellets were tested in 0.1 N HCl and phosphate buffer, pH 6.8. The addition of sodium croscarmellose (Ac-Di-Sol) did not influence the piroxicam release from microcrystalline cellulose pellets. Sodium carboxymethyl starch (Explotab) increased the release from 30 to 65% at 45 min. The incorporation of sodium carboxymethyl cellulose on its own or as a co-processed blend with microcrystalline cellulose (Avicel RC 581 and CL 611) enhanced the release of piroxicam at 45 min from 30% (pure Avicel PH 101) to 95% (combination of Avicel PH 101 and CL 611 in a ratio of 1:3). Additional use of cyclodextrins had only a minor influence on the dissolution rate. An Eudragit L 30 D-55 and FS 30 D (6/4) film was applied to the core pellets (containing 2.5% (w/w) piroxicam and a combination of Avicel PH 101 and CL 611 in a ratio of 1:3) in order to obtain gastroresistant properties. The coated pellets retained their dissolution characteristics after compression into fast disintegrating tablets because waxy cushioning beads were added to minimize film damage.     

Liquisolid technique: a promising alternative to conventional coating for improvement of drug photostability in solid dosage forms

Objective: The objective of this study was to investigate the photoprotective effect of liquisolid technique on amlodipine, a calcium channel blocker antihypertensive drug, representing a photosensitive drug model.

Method: Several liquisolid formulations were prepared using propylene glycol as a water-miscible nonvolatile vehicle at drug/solvent ratio (1:1), Avicel PH 102 as a carrier, nanometer-sized amorphous silicon and titanium dioxide either alone or in combination as coating materials. The carrier/coat ratio (R) was varied from 5 to 50. The prepared liquisolids, coated, noncoated tablets and drug substance were irradiated with a light dose of 0.5 W/m²/h visible light, 55.1 W/m²/h UVA, and 0.247 W/m²/h UVB for 8 h. The effect of coating material type and (R) value on the drug dissolution rate and photostability was studied. Results were statistically analyzed by post hoc two-way ANOVA at a probability level (α = 0.05).

Results: The results indicated that liquisolid technique not only improved the dissolution rate, but also significantly inhibited the photodegradative effect of different light energies in all prepared liquisolid formulations. The residual drug percentage reached 97.37% in comparison to 73.8% for the drug substance after 8 h of irradiation. The residual drug percentage was affected by the (R) value. Statistically; the detected difference was significant at the selected probability level (α = 0.05).

Conclusion: It can thus be concluded that this liquisolid technique is a promising alternative to conventional coating procedures in formulations containing photosensitive drugs.     

Improved solubility and dissolution rate of piroxicam using gelucire 44/14 and labrasol

Piroxicam is a nonsteroidal anti-inflammatory drug that is characterized by low solubility-high permeability. The present study was designed to improve the dissolution rate of piroxicam at the physiological pH's through its increased solubility by preparing semi-solid dispersions of drug using Gelucires and Labrasol. These excipients are essentially characterized by their melting points and HLB (hydrophilic-lipophilic balance) values. The dissolution tests of the preparations were performed in the media with different pH's. Differential scanning calorimetry (DSC), were used to examine the interaction between piroxicam and excipients. Gelucire 44/14 and Labrasol at the concentration of 15% w/v in water provided 20- and 50-fold increase in the solubility of piroxicam, respectively. The semi-solid dispersion containing 1/20 of drug/excipient mixture (20% Gelucire 44/14 and 80% Labrasol in w/w) produced the dissolution not less than 85% of piroxicam within 30 min in each dissolution media (simulated gastric fluid (SGF), pH 1.2; phosphate buffers, pH 4.5 and 6.8; and water). DSC analysis of this semi-solid dispersion indicated that there was no chemical reaction between the drug and excipients, and that a solid-state solution of piroxicam with excipient formed.     

Liquisolid technology for dissolution rate enhancement or sustained release

Importance of the field: Most of the drugs that have been invented are of BCS Class II. Therefore, dissolution rate enhancement is the key aspect for absorption of these drugs. Liquisolid technology is very efficient in the dissolution rate enhancement of these drugs. Moreover, use of other polymers such as Eudragit and hydroxypropyl methylcellulose in the liquisolid approach can cause sustained release of drugs. This review focuses on the formulation approaches of liquisolid tablets or compacts along with its fundamental principles.

Areas covered in this review: The review focuses on the developments in liquisolid technology from 1998 to 2009 with in vitro and in vivo performance of the dosage forms prepared using this technology.

What the reader will gain: Benefits of this review include a concise evaluation of this technology by focusing on the scope of future developments to be done using this technique.

Take home message: Liquisolid technology, the next generation of powder solution technology, can be helpful for enhancing dissolution rates of poorly water-soluble drugs as well as effective at sustaining drug release.     

Nanocrystals as tool to improve piroxicam dissolution rate in novel orally disintegrating tablets

In this paper, orally disintegrating tablets (ODT) were prepared using nanocrystal formulations in order to optimise dissolution properties of lipophilic, poorly soluble drug piroxicam (PRX). Different nanocrystal formulations were prepared using a high pressure homogenisation technique and poloxamer 188 as stabiliser. Characterisation of PRX nanocrystal ODT was carried out by infrared spectroscopy (FTIR), X-ray powder diffractometry (XRPD), differential scanning calorimetry and photon correlation spectroscopy. Dissolution study of PRX ODT was performed in distilled water (pH 5.5) and was compared to that of PRX coarse suspension ODT, PRX/poloxamer 188 physical mixture and bulk PRX samples. The XRPD and FTIR studies demonstrated that the homogenisation process led to a polymorphic transition from form I (bulk commercial PRX) to form III and monohydrate form of the nanocrystals. All ODT formulations prepared using PRX nanosuspensions showed a higher PRX dissolution rate compared with the ODT prepared with the coarse PRX. Since the solubility of the different PRX polymorphic forms increased only slightly from bulk PRX (form I) to monohydrate, form II and form III, we can conclude that the improvement in PRX dissolution rate is mainly caused by the increased surface-to-volume ratio due to the submicron dimension of the drug particles.