Fast-release Formulation Research Articles

Development of Doxazosin mesylate liquisolid system for improved manufacturing processability and bioavailability: in vitro and in vivo evaluation for tailored hypertension treatment approach with modified dissolution rates

In the present research, an attempt was made to optimize the blends of different carriers Neusiln US2, Avicel PH101, and Fujicalin SG by individually blending with each of coating materials Aerosil 200 and Syloid 244 FP that were proposed to contribute to a modified drug dissolution rates of Doxazosin mesylate (DX) through a liquisolid polymer matrix system. The liquisolid formulations were prepared using selected solvent, carriers, and coats by varying drug to polymer ratios. Further formulations were investigated for pre-compression processability by Heckel plot analysis, elastic recovery studies, and post-compression characteristics. In case of carriers, compared to Avicel PH101 highest flowable values (ф) were observed for Neusilin US2 and Fujicalin SG whereas, for coat these values were highest for Aerosil 200 than Sylloid 244 FP. Liquisolid compact with Fujicalin SG and Aerosil 200 exhibited fast release (FR) of 78% in 20 minutes. The liquisolid compact with Neusilin US2 and Syloid 244 FP exhibited prolonged release (PR) of 60% in 240 minutes. DSC and XRD analysis showed loss of DX crystallinity which was confirmed by SEM analysis indicating DX detention within the liquisolid system, in a molecularly dispersed solubilized form. The in vivo studies of DX liquisolid FR formulation exhibited 1.89 fold increase in the oral bioavailability which was 1.69 fold for DX PR formulation compared to pure DX which demonstrated a promising tailored hypertension treatment approach.

Formulation, Development, and in-vitro Evaluation of Escitalopram Fast Dissolving Tablets.

Escitalopram, a selective serotonin reuptake inhibitor (SSRI), acts by increasing the serotonin level in the brain and is used widely for the management of depression and anxiety disorders. However, the poor dissolution rate of escitalopram due to less water solubility is a consequential problem confronting the pharmaceutical industry in developing pharmaceutical dosage forms for oral delivery systems. The present work aims to deliver a novel formulation for improving the dissolution profile and, thus, the bioavailability of escitalopram. Fast Dissolving Tablets (FDT) are expected to enable quick drug release, which will improve the drug's dissolving profile, allowing for the initial increase in plasma concentration mandatory in an acute depression attack. The use of co-processed excipients in tablets has been shown to increase the compressibility and disintegration properties of the tablets, resulting in improved in-vitro drug release and bioavailability. As co-processed excipients, a mixture of banana powder (a natural super disintegrant with nutritional value) and microcrystalline cellulose (a highly compressible substance with good wicking and absorption capacity) was used. The tablets were made using a response surface, randomised central composite design, and a direct compression technique. The manufactured tablets were found to be released more than 95% of the drug within 10 minutes and showed an improved drug release profile than the available marketed formulation. After confirming in-vivo potential, the fast release formulation exhibited impressive in-vitro findings and may prove to be a boon in treating acute depression attacks.

FORMULATION AND EVALUATION OF ORAL FAST DISSOLVING FILMS OF NAPROXEN SODIUM

Objective: The aim of this investigation was to prepare ODFs containing Naproxen Sodium, an NSAID, using solvent casting method and to evaluate them to put together a dosage form which can be taken without water, is easy to administer, has a rapid onset of action and can surmount first pass metabolism. Six distinct formulations of naproxen sodium ODF (F1-F6) were created in this investigation by varying the quantity of croscarmellose sodium, a super disintegrant.
 Methods: Naproxen Sodium ODF’s were prepared by solvent casting method. Evaluation of prepared ODF’s was done by considering various parameters such as film thickness, folding endurance, disintegration time, surface pH, weight variation, in vitro dissolution test, content uniformity and FTIR.
 Results: F6 has shown to be the best fast release formulation in terms of disintegration time (less than 1 minute) and dissolution (103.5 % after 30 min). Formulation F6's other film characteristics, such as weight variation, thickness, pH, and folding endurance, were all within the USP limit.
 Conclusion: By virtue of quick disintegration self-administration without water or chewing, oral fast dissolving film (OFDF) is one such new technique to enhance consumer acceptance. The film is an excellent intraoral fast-dissolving medication delivery method by which a wide range of medicines, including neuroleptics, cardiovascular drugs, analgesics, anti-asthmatic, antihistamines and drugs for erectile dysfunction, can be manufactured. From the standpoint of the patient, oromucosal medication delivery is appealing since it allows for easy administration without the need to swallow, as well as better patient safety. As a novel delivery mechanism, the notion of a quick-dissolving dosage form has gained popularity. By lowering dose frequency, this method will deliver optimum therapeutic efficacy, improved bioavailability, and maximum stability. This will also surmount first-pass metabolism of drugs. This method allows for faster medication absorption from the pre-gastric region, perhaps resulting in a faster onset of action.

Evaluating the IVIVC by Combining Tiny-tim Outputs and Compartmental PK Model to Predict Oral Exposure for Different Formulations of Ibuprofen

Nowadays, the ever-increasing costs of research and development in the pharmaceutical industry have created a big demand for predicting the performances of drug candidates. Of those, the desire to establish an in vitro-in vivo correlation (IVIVC) to better predict the oral drug exposure for different drug products is a growing need. Once a robust IVIVC is established, the performance of different drug products can be predicted and selected for testing in clinical trials with greater confidence. This tool will significantly reduce the cost and speed of drug development and provide new therapy to the patient faster. In this study, we explore combining the outputs of Triskelion's Gastro-Intestinal Model (Tiny-TIM) and multi-compartment pharmacokinetic model for a 200 mg ibuprofen product. The Loo-Riegelman method was used to calculate the amount of ibuprofen absorbed and was combined with the Tiny-TIM data to establish the IVIVC. The IVIVC was used to predict the exposures of both fast release and liquid gel formulations in humans. In general, the predicted exposure using Tiny-TIM-based IVIVC has good agreement with the clinical findings.

Optimizing overnight oral appliance for sustained-release varnish delivery system of sirolimus

<h3>Objectives</h3> Intraoral trays can be used to deliver treatment materials and medications for dental or mucosal conditions. Maintaining appropriate salivary levels of the active ingredient is challenging when using local application. We have previously analyzed salivary levels and local effects of slow-release varnishes (with clotrimazole or sirolimus as the active ingredient) during the daytime. The aims of the present study were as follows: (1) to optimize overnight appliances for slow-release medications by measuring saliva and blood levels and (2) to evaluate the safety of overnight use. <h3>Methods</h3> An acrylic tray containing 0.5 mg of sirolimus in a sustained-release varnish was applied to 6 anterior teeth for 12 hours in 10 healthy volunteers. Whole unstimulated saliva was collected 1, 2, 10, and 12 hours after application, and a blood sample was taken after 12 hours. Drug levels were analyzed. Results from slow- and fast-release formulations, varnish application position on the tray (buccal, palatal, or lingual), and tray placement (mandibular vs maxillary) were compared. The volunteers evaluated the varnish and tray. The study was approved the hospital ethics committee. <h3>Results</h3> Salivary sirolimus was undetected with use of the slow formulation. The faster formulation produced salivary concentrations of 0.3-45 ng/mL. The highest salivary levels were observed with a mandibular tray with lingual varnish application (up to 178 ng/mL). The sialometry of all participants was within normal range (0.2-2 mL/min), and the highest drug levels were found when salivary flow was lowest. The medication was undetected in the blood. No local reactions or side effects were reported. <h3>Conclusions</h3> Salivary concentrations of medications delivered using an oral tray can be affected by the release rate of formulation and, more important, by the position of the tray and the varnish within it and salivary flow rate. Overnight oral trays can be used to deliver medications especially when 24-hour drug exposure is desired. Further studies regarding local factors affecting drug release and salivary levels are required.

Prediction of in vivo performance of oral extended release formulations prior to clinical evaluation: A case study for enteric coated polymeric beads formulation

To reduce cost and time for product development, an ideal strategy for the development of oral extended release (ER) product is to identify the desired formulation with minimum needsfor clinical evaluation. The aim of this work was to demonstrate the feasibility of adopting a “prediction-then-validation” strategy for the development of oral ER formulations. Instead of the traditional approach using multiple ER formulations for IVIVC development, an enteric-coated fast release formulation was successfully utilized for the development of a biopredictive tool to estimate the drug release from enteric coated polymeric ER formulations in the intestine. A TS1 (time scale factor between Tvitro and Tvivo equals to 1) system was designed and developed, based on which the in vivo pharmacokinetic (PK) performance of ER formulations in dog and in human were well predicted prior to in vivo evaluations. The model further passed a posteriori validation using the criteria for level A IVIVC and, as designed, provided a Tscale value of 1 for the IVIVC model.

Formulation and in vitro Evaluation of Fast Dissolving Tablets of Febuxostat Using Co-Processed Excipients.

BackgroundFebuxostat is a novel, orally-administered, powerful, non-purine, xanthine oxidase inhibitor used for treating gout and ceaseless tophaceous gout. The drug exhibits low bioavailability (about 49%) which is ascribed to its dissolution rate-limited absorption.ObjectiveThe current work is aimed to provide a novel strategy to improve the dissolution profile and thus, the bioavailability of Febuxostat.MethodsFormulation of Fast Dissolving Tablets (FDT) is anticipated to provide immediate release of the drug, which in turn, will improve its dissolution profile to provide the initial surge in plasma concentration required in an acute gout attack. Incorporation of co-processed excipients in a tablet is known to improve the compressibility and disintegration characteristics of the tablets, which, in turn, result in enhanced in vitro drug release and improved bioavailability. A combination of crospovidone (it rapidly wicks saliva into the tablet to create the volume development and hydrostatic weight important to give quick disintegration) and microcrystalline cellulose (a highly compressible ingredient with good wicking and absorbing capacity) was, therefore, used as co-processed excipients.ResultsThe tablets were prepared by direct compression technique with the application of a 32 randomized full factorial design. The prepared tablets were able to release more than 80% of the drug within 10 minutes of the start of dissolution testing and were able to show a better drug release profile in comparison to available marketed formulation.ConclusionSo, it can be concluded that the developed fast release formulation was found to exhibit convincing in vitro results and may prove a boon in the treatment of acute gout attack after establishing in vivo potential.

English

The aim of this present study was to develop and formulate sustained release coated metoprolol tartrate matrix granules and to design an in-vitro in-vivo correlation (IVIVC) tool based on bioavailability data available from human volunteers. USP apparatus II, paddle type was used for generation of in-vitro drug release data for each formulation. The similarity factor (f2) was determined using dissolution data parameters of the formulations. Twenty-four healthy male volunteers participated in the two-way crossover bioequivalent study where the volunteers were treated in a completely randomized fashion. The percent drug dissolved in the dissolution test and percent absorbed data shows a ‘level A’ IVIVC was achieved with a good linear regression relation. Different release rate formulation including Fast, Moderate and Slow release formulations exhibited an excellent covenant between the three dosage forms. Key words: Sustained-release capsules, metoprolol tartrate, bioavailability, in-vitro in-vivo correlation (IVIVC), humans.

In vivo fate of lipid-silybin conjugate nanoparticles: Implications on enhanced oral bioavailability

Lipid-drug conjugates (LDCs) of a poorly soluble and poorly permeable drug silybin (SB) and lipids with different chain lengths (6C, 12C, 18C) are synthesized and formulated into solid lipid nanoparticles (SLNs). The in vivo fate of LDCs as well as SLNs is investigated by tracking either SB or LDCs or SLNs. LDCs are prone to be hydrolyzed by lipases either in simulated gastrointestinal media or in Caco-2 cell lines in a lipid chain length-dependent mode. The oral bioavailability of SB is enhanced by 5–7-fold in comparison with a fast-release formulation. No integral LDCs are detected in plasma confirms the readily degradable nature of LDCs. The absorption of LDCs by enteric epithelia and subsequent transportation into circulation might play a leading role in absorption enhancement, whereas the contribution of then M-cell pathway is not as remarkable. A shorter lipid chain favors earlier lipolysis and faster absorption along the intestine-to-circulation path.

Controlling Release of Integral Lipid Nanoparticles Based on Osmotic Pump Technology.

To achieve controlled release of integral nanoparticles by the osmotic pump strategy using nanostructured lipid carriers (NLCs) as model nanoparticles. NLCs was prepared by a hot-homogenization method, transformed into powder by lyophilization, and formulated into osmotic pump tablets (OPTs). Release of integral NLCs was visualized by live imaging after labeling with a water-quenching fluorescent probe. Effects of formulation variables on in vitro release characteristics were evaluated by measuring the model drug fenofibrate. Pharmacokinetics were studied in beagle dogs using the core tablet and a micronized fenofibrate formulation as references. NLCs are released through the release orifices of the OPTs as integral nanoparticles. Near zero-order kinetics can be achieved by optimizing the influencing variables. After oral administration, decreased C max and steady drug levels for as long as over 24h are observed. NLC-OPTs show an oral bioavailability of the model drug fenofibrate similar to that of the core tablets, which is about 1.75 folds that of a fast-release formulation. Controlled release of integral NLCs is achieved by the osmotic pump strategy.

Abuse-Deterrent Opioid Formulations: Pharmacokinetic and Pharmacodynamic Considerations.

Abuse-deterrent formulations (ADFs) are technologically sophisticated pharmaceutical formulations that impede manipulation and extraction of opioids and/or provoke unpleasant effects when they are taken in excessive quantity. This is implemented by creating physical barriers, inseparably combining the opioid with an opioid antagonist or adding aversive agents to the formulation. These pharmaceutical changes may potentially alter the pharmacokinetics and consequently the pharmacodynamics of the opioid. In this review, comparative evidence on pharmacokinetic differences between abuse-deterrent and classical formulations of the same opioids is summarized; furthermore, pharmacodynamic differences, with a focus on analgesia and abuse-related symptoms, are addressed. Most of the 12 studies comparing opioid pharmacokinetics have judged the physically intact ADF as being bioequivalent to the corresponding classical formulation. Pharmacokinetic differences have, however, been reported with physically manipulated ADFs and have ranged from moderate deviations from bioequivalence to complete changes in the pharmacokinetic profile (e.g. from a sustained-release formulation to a fast-release formulation). Pharmacodynamic effects were assessed in 14 comparative studies, which reported that intact ADFs usually provided clinically equivalent analgesia and clear advantages with respect to their addiction potential. However, withdrawal symptoms could be induced by the ADFs, although rarely and, in particular, when the ADFs had been physically altered. This evidence suggests that opioid ADFs are a working concept resulting in mostly minor pharmacokinetic and pharmacodynamic differences in comparison with classical formulations; however, they may deviate from this equivalence when physically altered.

The role of lipid-based nano delivery systems on oral bioavailability enhancement of fenofibrate, a BCS II drug: comparison with fast-release formulations.

The aim of this study was to compare various formulations solid dispersion pellets (SDP), nanostructured lipid carriers (NLCs) and a self-microemulsifying drug delivery system (SMEDDS) generally accepted to be the most efficient drug delivery systems for BCS II drugs using fenofibrate (FNB) as a model drug. The size and morphology of NLCs and SMEDDS was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Their release behaviors were investigated in medium with or without pancreatic lipase. The oral bioavailability of the various formulations was compared in beagle dogs using commercial Lipanthyl® capsules (micronized formulation) as a reference. The release of FNB from SDP was much faster than that from NLCs and SMEDDS in medium without lipase, whereas the release rate from NLCs and SMEDDS was increased after adding pancreatic lipase into the release medium. However, NLCs and SMEDDS increased the bioavailability of FNB to 705.11% and 809.10%, respectively, in comparison with Lipanthyl® capsules, although the relative bioavailability of FNB was only 366.05% after administration of SDPs. Thus, lipid-based drug delivery systems (such as NLCs and SMEDDS) may have more advantages than immediate release systems (such as SDPs and Lipanthyl® capsules).

Recombinant human bone morphogenetic protein‐type 2 (rhBMP‐2) enhances local bone formation in the lumbar spine of osteoporotic sheep

The failure of orthopedic implants in osteoporotic patients is attributed to the lack of sufficient bone stock and regenerative capacity but most treatments for osteoporosis fail to address this issue. rhBMP-2 is known to promote bone formation under normal conditions but has not been used clinically in the osteoporotic condition. Osteoporosis was induced in 19 ewes using ovariectomy, low calcium diet, and steroid injection. After induction, the steroid was withdrawn and pellets containing inert carrier with rhBMP-2 in either slow or fast-release formulation were implanted into the lumbar vertebrae of each animal. After 2, 3, and 6 months the spines were harvested and assessed for changes in BMD and histomorphometric indices. BMD did not change after cessation of steroid treatment. After 2 months BV/TV increased in the vicinity of the pellets containing the fast-release rhBMP-2 and was sustained for the duration of the study. Focal voids surrounding all implants, particularly the slow-release formulation, were observed initially but resolved with time. Increased BV/TV adjacent to rhBMP-2 pellets suggests it could be used for localized treatment of osteoporosis. Refinement of the delivery system and supplementary treatments may be necessary to overcome the initial catabolic effects of rhBMP-2.

Use of In Vitro–In Vivo Correlation to Predict the Pharmacokinetics of Several Products Containing a BCS Class 1 Drug in Extended Release Matrices

To determine if an IVIVC model can predict PK profiles of varying formulations of a BCS Class 1 drug that is a salt of a weak base. An IVIVC model (Level A) was created by correlating deconvoluted in vivo absorption data obtained from oral administration of 50 mg, 100 mg, and 200 mg fast and slow extended release formulations with in vitro percent dissolved using residual regression analysis. The model was then used to predict the in vivo profile of five test products that varied in formulation characteristics. The model passed internal validation for predicted Cmax and AUC. For external validation, in vitro data of five different test formulations was utilized. The model passed external validation for two test formulations that were different but belonging to the same release mechanism as that of the reference formulation. Three formulations failed external validation because they belonged to either a mixed or different release mechanism. The model and results were further confirmed using GatstroPlus™ simulation software. These observations indicate that an IVIVC model for a BCS class I drug may be applicable to varying formulations if the principle of the drug release is similar.

Effects of the mucoadhesive polymer polycarbophil on the intestinal absorption of a peptide drug in the rat.

The absorption across rat intestinal tissue of the model peptide drug 9-desglycinamide, 8-arginine vasopressin from bioadhesive formulations was studied in-vitro, in a chronically isolated internal loop in-situ and after intraduodenal administration in-vivo. A controlled-release bioadhesive drug delivery system was tested, consisting of microspheres of poly(2-hydroxyethyl methacrylate) with a mucoadhesive Polycarbophil-coating, as well as fast-release formulation consisting of an aqueous solution of the peptide in a suspension of Polycarbophil particles. Using the controlled-release system, a slight improvement of peptide absorption was found in-vitro in comparison with a non-adhesive control system, but not in-situ or in-vivo. In contrast, bioavailability was significantly increased in all three models from the Polycarbophil suspension in comparison with a solution of the drug in saline. The effect appeared to be dose-dependent, indicative of intrinsic penetration-enhancing properties of the mucoadhesive polymer. A prolongation of the absorption phase in-vitro and in the chronically isolated loop in-situ suggested that the polymer was able to protect the peptide from proteolytic degradation. This could be confirmed by degradation studies in-vitro. The duration of the penetration enhancing/enzyme inhibiting effect was diminished with increasing complexity of the test model, in the same way as was previously found for the bioadhesive effect. This interrelationship suggests that the observed improvement in peptide absorption and the mucoadhesive properties of this polymer are associated. The development of a fast-release oral dosage form for peptide drugs on the basis of Polycarbophil appears to be possible.

Usefulness of Sweat Testing for the Detection of Methylphenidate After Fast- and Extended-Release Drug Administration: A Pilot Study

The pharmacokinetics of methylphenidate (MPH), a prescription amphetamine derivative used in the treatment of attention-deficit hyperactivity disorder, has been amply described in conventional biological matrices. Recently, the excretion of MPH and its principal metabolite, ritalinic acid (RA) in oral fluid and plasma after a single drug administration has been described. The aim of this study was to describe the excretion of MPH and RA in sweat after the administration of a single dose of either fast-release or extended-release MPH. Three male subjects received 2 simultaneous oral doses of 10 mg fast-release MPH, and 1 male subject received one dose of 20 mg extended-release MPH. Sweat patches were applied to the back of each participant and removed at timed intervals. MPH and RA were determined in patches using a previously validated liquid chromatography-electrospray ionization mass spectrometric method. MPH was detected in sweat after the administration of fast- and extended-release formulations. For the fast-release formulation, MPH appeared in the sweat patches 2 hours after administration with a maximum of 15.9 nanogram per patch, reached after 24 hours. Mean total MPH excreted was 0.02 mg (about 0.08% of the administered dose). For the extended-release formulation, MPH appeared in the sweat 5 hours after administration and reached a maximum of 34.3 nanogram per patch after 24 hours. Mean total MPH excreted was 0.04 mg (about 0.18% of the administered dose). RA was not detected in either of the sweat patches probably because of its acidic properties. Measuring MPH in sweat patches can be a viable alternative to urine testing for noninvasive monitoring of use and misuse of the drug.

Correlation Between Methylphenidate and Ritalinic Acid Concentrations in Oral Fluid and Plasma

We studied the excretion profile of methylphenidate (MPH) and its metabolite ritalinic acid (RA) in oral fluid and plasma, the oral fluid-to-plasma (OF/P) drug ratio, and the variations of oral fluid pH after drug administration. We analyzed oral fluid and plasma samples, obtained from 8 healthy volunteers after ingestion of a single dose of 20 mg fast-release or extended-release MPH, for MPH and RA by LC-MS. We estimated the apparent pharmacokinetic parameters of MPH in plasma and oral fluid and calculated the OF/P ratio for each time interval. MPH and RA were detected in oral fluid. Whereas parent drug concentrations in oral fluid were an order of magnitude higher than those in plasma, the opposite was observed for RA. Oral fluid concentrations of MPH ranged between 0.5 and 466.7 microg/L and peaked at 0.5 h after administration of the fast-release formulation; they ranged between 0.7 and 89.5 microg/L and peaked at 2 h after administration of the extended-release formulation. Both formulations presented bimodal time-course curves for the OF/P ratio, ranging between 1.8 and 242.1 for the fast-release formulation and between 2.6 and 27.0 for extended-release. Oral fluid pH did not appear to be modified by the administration of the drug, and its influence on OF/P ratio did not affect the correlation of MPH between the 2 body fluids. The results obtained support the measurement of MPH in oral fluid as an alternative to plasma if the extended-release formulation is used.

Direct, differential-equation-based in-vitro-in-vivo correlation (IVIVC) method.

A new, differential equation-based in-vitro-in-vivo correlation (IVIVC) method is proposed that directly relates the time-profiles of in-vitro dissolution rates and in-vivo plasma concentrations by using one- or multi-compartment pharmacokinetic models and a corresponding system of differential equations. The rate of in-vivo input is connected to the rate of in-vitro dissolution through a general functional dependency that allows for time scaling and time shifting. A multiplying factor that accounts for the variability of absorption conditions as the drug moves along is also incorporated. Two data sets incorporating slow-, medium-, and fast-release formulations were used to test the applicability of the method, and predictive powers were assessed with a leave-one-formulation-out approach. All fitted parameters had realistic values, and good or acceptable fits and predictions were obtained as measured by plasma concentration mean squared errors and percent AUC errors. Introduction of step-down functions that account for the transit of the dosage form past the intestinal sites of absorption proved useful. By avoiding the integral transforms used in the existing deconvolution- or convolution-based IVIVC models, the present method can provide increased transparency, improved performance, and greater modelling flexibility.

In-vitro and in-vivo correlation for two gliclazide extended-release tablets

The aim of this study was to perform an in-vitro-in-vivo correlation (IVIVC) for two 60-mg gliclazide extended-release formulations (Fast and Slow release) given once a day and to compare their plasma concentrations over time. In-vitro release rate data were obtained for each formulation using the USP apparatus II, paddle stirrer at 50 and 100 rev min(-1) in 0.1 M HCl and pH 7.4 phosphate buffer. The similarity factor (f2) was used to analyse the dissolution data. Eighteen healthy subjects participated in the study, conducted according to a completely randomized, two-way crossover design. The formulations were compared using area under the plasma concentration-time curve, AUC(0-infinity), time to reach peak plasma concentration, Tmax, and peak plasma concentration Cmax, while correlation was determined between in-vitro release and in-vivo absorption. A linear correlation model was developed using percent absorbed data versus percent dissolved data from the two formulations. Predicted gliclazide concentrations were obtained by use of a curve fitting equation. Prediction errors were estimated for Cmax and area under the curve AUC(0-infinity) to determine the validity of the correlation. 0.1 M HCl at 50 rev min(-1) was found to be the most discriminating dissolution method. Linear regression analysis of the mean percentage of dose absorbed versus the mean percentage of in-vitro release resulted in a significant correlation (r2 > 0.98) for the two formulations. An average percent prediction error for Cmax was 4.15% for Fast release and 3.99% for Slow release formulation whereas for AUC(0-infinity) it was 6.36% and 4.66% for Fast release and Slow release formulation, respectively.

Ni2+-mediated mitoxantrone encapsulation: Improved efficacy of fast release formulation

Despite that in solution we cannot detect the interaction between Ni2+ and mitoxantrone (MIT), Ni2+ could mediate effective and stable MIT loading into large unilamellar vesicles (LUVs). The presence of nigericin had almost no influences on MIT encapsulation. However, in the presence of NH3, the drug loading kinetics significantly altered. UV–vis spectrum analysis revealed that the absorption profile of liposomal MIT prepared with NiSO4 gradient method was markedly different from that of liposomal MIT prepared with pH gradient method and that of free MIT. Three liposomal formulations were prepared, which were made from DMPC/chol, DPPC/chol and HSPC/chol and named LM-m, LM-p and LM-s. The in vitro release T1/2 values for the formulations were 15.0, 28.2 and 38.5h, respectively. Following an intravenous injection into BDF1 mice at a dose of 4mg/kg, the MIT plasma levels at 24h time point were 3.3, 11.3 and 12.7μg/mL, considerably compared to that of free MIT group. In L1210 ascitic model, LM-m therapy resulted in ∼60% long-term survivor (>60 days), and increased survival times in comparison with other treatments. However, both LM-p and LM-s formulations were less therapeutically active than free MIT. In conclusion, transmembrane NiSO4 gradient could mediate effective MIT loading, and the formulation prepared with fluid lipid had fast release rate and improved efficacy in L1210 ascitic tumor model.