The solubility-modulated osmotic pump: in vitro/in vivo release of diltiazem hydrochloride

3D Printing Technology as a Promising Tool to Design Nanomedicine-Based Solid Dosage Forms: Contemporary Research and Future Scope

3D printing technology in medicine is gaining great attention from researchers since the FDA approved the first 3D-printed tablet (Spritam®) on the market. This technique permits the fabrication of various types of dosage forms with different geometries and designs. Its feasibility in the design of different types of pharmaceutical dosage forms is very promising for making quick prototypes because it is flexible and does not require expensive equipment or molds. However, the development of multi-functional drug delivery systems, specifically as solid dosage forms loaded with nanopharmaceuticals, has received attention in recent years, although it is challenging for formulators to convert them into a successful solid dosage form. The combination of nanotechnology with the 3D printing technique in the field of medicine has provided a platform to overcome the challenges associated with the fabrication of nanomedicine-based solid dosage forms. Therefore, the major focus of the present manuscript is to review the recent research developments that involved the formulation design of nanomedicine-based solid dosage forms utilizing 3D printing technology. Utilization of 3D printing techniques in the field of nanopharmaceuticals achieved the successful transformation of liquid polymeric nanocapsules and liquid self-nanoemulsifying drug delivery systems (SNEDDS) to solid dosage forms such as tablets and suppositories easily with customized doses as per the needs of the individual patient (personalized medicine). Furthermore, the present review also highlights the utility of extrusion-based 3D printing techniques (Pressure-Assisted Microsyringe-PAM; Fused Deposition Modeling-FDM) to produce tablets and suppositories containing polymeric nanocapsule systems and SNEDDS for oral and rectal administration. The manuscript critically analyzes contemporary research related to the impact of various process parameters on the performance of 3D-printed solid dosage forms.

Preparation and evaluation of bilayer-core osmotic pump tablets contained topiramate

Topiramate (TPM) was an antiepileptic agent commonly used in clinical. Studies showed that an oral preparation of TPM with extended-release manner could bring some benefits for epileptics. In this paper, controlled release push-pull osmotic pump (PPOP) tablets of sparingly water-soluble TPM were successfully prepared. This bi-layer tablet core mainly consisted of sodium chloride as osmotic promoting agent and polyethylene oxide as suspending and pushing agents. The influences of osmotic agents, pushing agents and the compositions of coating membrane on TPM release profiles were evaluated. An optimal formulation of TPM-PPOP was obtained through single-factor experiments. In vitro release tests showed that the optimum formulation could release TPM at an approximate zero-order rate up to 8 h. Pharmacokinetic behaviors of TPM-PPOP tablets were evaluated and compared with the immediate release capsules after an oral single dose in beagle dogs. Pharmacokinetics results demonstrated that the TPM-PPOP tablet was able to provide a prolonged release of TPM with longer tmax and mean residence time. Lower fluctuations of drug plasma levels could also be achieved with TPM-PPOP tablets. These results suggested that sparely water-soluble drugs as TPM can be designed to PPOP for efficacy and safety use.

Quality by Design (QbD)-Based Numerical and Graphical Optimization Technique for the Development of Osmotic Pump Controlled-Release Metoclopramide HCl Tablets

PURPOSE

To develop the osmotically controlled-release gastroprokinetic metoclopramide HCl tablets, using quality by design (QbD)-numerical and graphical optimization technique for the treatment of gastroparesis and prophylaxis of delayed nausea and vomiting induced by low-high emetogenic chemotherapy.

METHODS

Formulations were designed by central composite design using Design Expert version 11.0.0, with osmogen concentration (X1), orifice size (X2), and tablet weight gain after coating (X3) as input and in-vitro drug release at 1hr. (Y1), 6 hrs. (Y2), and 12 hrs. (Y3), and the regression coefficient of drug release data fitted to zero-order, RSQ zero (Y4) as output variables. Core tablets prepared by direct compression were coated with Opadry® CA. The experimental design was validated by the polynomial equation. A correlation between predicted and observed values was evaluated by random checkpoint analysis. The optimized formulations were characterized for drug release, pH effect, osmolarity, agitation intensity, surface morphology, and stability study, and were subjected to accelerated studies according to ICH guidelines.

RESULTS

The interaction charts and response surface plots deduced a significant simultaneous effect of X variables on in vitro drug release and RSQ zero. The numerical optimization model predicted >90% drug release with X1 (13.30%), X2 (0.6 mm), and X3 (7.96%). Random checkpoint analysis showed a good correlation between predicted and observed values. The optimized formulation followed zero-order kinetics (r2=0.9703) drug release. Shelf life calculated was 2.8 years as per ICH guidelines.

CONCLUSION

The QbD-based approach was found successful in developing controlled release osmotic tablets of metoclopramide HCl, for reducing the dosage frequency, better emetic control, and improve patient compliance.

Development of a Multivariate Predictive Dissolution Model for Tablets Coated with Cellulose Ester Blends

The focus of the present investigation was to develop a predictive dissolution model for tablets coated with blends of cellulose acetate butyrate (CAB) 171-15 and cellulose acetate phthalate (C-A-P) using the design of experiment and chemometric approaches. Diclofenac sodium was used as a model drug. Coating weight gain (X₁, 5, 7.5 and 10%) and CAB 171-15 percentage (X₂, 33.3, 50 and 66.7%) in the coating composition relative to C-A-P and were selected as independent variables by full factorial experimental design. The responses monitored were dissolution at 1 (Y₁), 8 (Y₂), and 24 (Y₃) h. Statistically significant (p < 0.05) effects of X₁ on Y₁ and X₂ on Y₁, Y_2, and Y₃ were observed. The models showed a good correlation between actual and predicted values as indicated by the correlation coefficients of 0.964, 0.914, and 0.932 for Y₁, Y_2, and Y₃, respectively. For the chemometric model development, the near infrared spectra of the coated tablets were collected, and partial least square regression (PLSR) was performed. PLSR also showed a good correlation between actual and model predicted values as indicated by correlation coefficients of 0.916, 0.964, and 0.974 for Y₁, Y₂, and Y₃, respectively. Y₁, Y_2, and Y₃ predicted values of the independent sample by both approaches were close to the actual values. In conclusion, it is possible to predict the dissolution of tablets coated with blends of cellulose esters by both approaches.

Zero-order drug delivery: State of the art and future prospects

Pharmaceutical drugs are an important part of the global healthcare system, with some estimates suggesting over 50% of the world's population takes at least one medication per day. Most drugs are delivered as immediate-release formulations that lead to a rapid increase in systemic drug concentration. Although these formulations have historically played an important role, they can be limited by poor patient compliance, adverse side effects, low bioavailability, or undesirable pharmacokinetics. Drug delivery systems featuring first-order release kinetics have been able to improve pharmacokinetics but are not ideal for drugs with short biological half-lives or small therapeutic windows. Zero-order drug delivery systems have the potential to overcome the issues facing immediate-release and first-order systems by releasing drug at a constant rate, thereby maintaining drug concentrations within the therapeutic window for an extended period of time. This release profile can be used to limit adverse side effects, reduce dosing frequency, and potentially improve patient compliance. This review covers strategies being employed to attain zero-order release or alter traditionally first-order release kinetics to achieve more consistent release before discussing opportunities for improving device performance based on emerging materials and fabrication methods.

Fabrication of an osmotic 3D printed solid dosage form for controlled release of active pharmaceutical ingredients

In pharmaceutical formulations, pharmacokinetic behavior of the Active Pharmaceutical Ingredients (API's) is significantly affected by their dissolution profiles. In this project, we attempted to create personalized dosage forms with osmotic properties that exhibit different API release patterns via Fused Deposition Modelling (FDM) 3D printing. Specifically, cellulose acetate was employed to create an external shell of an osmotically active core containing Diltiazem (DIL) as model drug. By removing parts of the shell (upper surface, linear lateral segments) were created dosage forms that modify their shape at specific time frames under the effect of the gradually induced osmotic pressure. Hot-Melt Extrusion (HME) was employed to fabricate two different 3DP feeding filaments, for the creation of either the shell or the osmotic core (dual-extrusion printing). Printed formulations and filaments were characterized by means of (TGA, XRD, DSC) and inspected using microscopy (optical and electron). The mechanical properties of the filaments were assessed by means of micro- and macro mechanical testing, whereas micro-Computed Tomography (μCT) was employed to investigate the volumetric changes occurring during the hydration process. XRD indicated the amorphization of DIL inside HME filaments and printed dosage forms, whereas the incorporated NaCl (osmogen) retained its crystallinity. Mechanical properties' testing confirmed the printability of produced filaments. Dissolution tests revealed that all formulations exhibited sustained release differing at the initiation time of the API dissolution (0, 120 and 360 min for the three different formulations). Finally, μCT uncovered the key structural changes associated with distinct phases of the release profile. The above results demonstrate the successful utilization of an FDM 3D printer in order to create osmotic 3D printed formulations exhibiting sustained and/or delayed release, that can be easily personalized containing API doses corresponding to each patient's specific needs.

Cellulose Acetate Butyrate: Ammonio Methacrylate Copolymer Blends as a Novel Coating in Osmotic Tablets

The objective of this work was the preparation of osmotic tablets using polymer blends of cellulose acetate butyrate (CAB) or ethylcellulose with ammonio methacrylate copolymer (Eudragit® RL). The advantage of these coatings in comparison to the traditionally used cellulose acetate is their solubility in safer organic solvents like ethanol. Polymer films were characterized with respect to their water uptake, dry mass loss, and mechanical properties. The effect of the polymer blend ratio on drug release and on the rupture force of the coating was investigated. In addition, the effect of drug solubility and content, pH and agitation rate of the release medium, and coating level and plasticizer content on the release were studied. With increased Eudragit® RL content in the coating blends, higher medium uptake of the film was observed, resulting in shorter lag times and faster drug release from the osmotic tablets. Replacing ethylcellulose with cellulose acetate butyrate as a coating material led to shorter lag times and faster drug release due to increased film permeability. In addition, CAB-based films had a higher strength and flexibility. The drug release was osmotically controlled and decreased with increasing coating level. It increased with increased drug solubility, plasticizer content, change of buffer species (acetate > phosphate), and decreased coating level. Agitation rate and drug content had no effect on the drug release. A 20% w/w coating level was sufficient for the tablet to tolerate forces of more than five times of the gastric destructive force reported in literature.

The development and evaluation of a subcutaneous infusion delivery system based on osmotic pump control and gas drive

A novel, self-administration drug delivery system for subcutaneous infusion was developed and evaluated. The device includes two main components: an osmotic tablet controlled gas actuator and a syringe catheter system. The sodium carbonate in the osmotic pump tablet will release into the surround citric acid solution and produce CO₂ gas, which will drive the drug solution into subcutaneous tissue. The key formulation factors of the osmotic tablet that would influence the infusion profiles of the device were investigated by single factor exploration. The formulation was optimized via a response surface methodology. With an 18 ± 4 min of lag time, the delivery system was able to infuse at an approximate zero-order up to 5.90 ± 0.37 h with a precision of 9.0% RSD (n = 6). A linear correlation was found for the infusion profile and the fitting equation was Y = 0.014X - 0.004 (r = 0.998). A temperature change of 4 °C was found to modify the flow rate by about 12.0%. In vivo results demonstrated that the present subcutaneous infusion device was similar to the commercial infusion pump, and it could bring a long and constant ampicillin plasma level with minimized fluctuations.

Effect of solvent on retarding the release of diltiazem HCl from Polyox-based liquisolid tablets

Objectives

The aim of this work was to investigate the use of liquisolid technique to sustain the release of a model highly soluble drug, diltiazem HCl, from liquisolid matrices containing Polyox, a recently proposed matrix-forming hydrophilic polymer as an alternative to hypromellose.

Methods

Polyox-based liquisolid formulations prepared using several non-volatile solvents (i.e. polysorbate 80, polyethylene glycol, polyethylene glycol 200 and polyethylene glycol 600) and then characterised using differential scanning calorimetry and powder X-ray diffraction. The influence of solvent on retarding the release of diltiazem HCl from Polyox-based liquisolid tablets compared to conventional physical mixture tablets was studied.

Key findings

Liquisolid tablets exhibited greater retarding properties compared to conventional tablets. The use of polysorbate produced a slower release pattern of the drug from diltiazem hydrochloride (DTZ) liquisolid tablets compared to propylene glycol and polyethylene glycol (200 and 600). The release retardation was decreased with the increase in the concentration of the drug within drug:solvent liquid medication used. Solid-state analysis suggested the presence of a fraction of the drug mass in a solubilised state within polysorbate in liquisolid powders.

Conclusion

Polyox-based matrix tablets prepared using liquisolid technique in the presence of a carefully selected non-volatile solvent could produce desirable, more sustained release profiles of highly water-soluble drugs compared to conventional physical mixture tablets.

Development and Evaluation of a Once-Daily Controlled Porosity Osmotic Pump of Tapentadol Hydrochloride

The present study aimed to prepare, optimize, and evaluate Tapentadol hydrochloride controlled porosity osmotic pump (CPOP) and to achieve the drug release at nearly zero-order. The CPOP was prepared by the coating of polymers (Eudragit RSPO and RLPO) on a directly compressed core tablet. A Box-behnken experimental design was applied to optimize the parameters for CPOP. The optimized batch was characterized for in vitro drug release study, effect of pH, osmolarity and agitation intensity, and surface morphology and stability study. In vivo pharmacokinetic studies were performed on New Zealand white rabbits for CPOP and marketed tablet. All the batches showed a drug release ranging from 29.87 to 56.92% after 12 h; and from 59.64 to 99.96% after 24 h. There was no change in the drug release pattern at different pH and agitation intensities. The drug release was found to decrease with increasing osmolarity of dissolution media.An in vivo study showed a higher mean residence time, area under the curve, and biological half-life (T 1/2) than the marketed tablet with low rate of elimination (Ke) and a 2.35-fold increase in relative bioavailability. The result showed that the amounts of sodium chloride and PEG 400 were contributing positively while the number of coats was negatively affecting the drug release. The drug release was found to be independent of physiological conditions. The stability testing showed that the prepared CPOP was stable for 3 months at accelerated conditions. The prepared CPOP was found to deliver Tapentadol hydrochloride at zero-order for up to 24 h.

Design and development of controlled porosity osmotic tablet of diltiazem hydrochloride

The present work aims towards the design and development of extended release formulation of freely water-soluble drug diltiazem hydrochloride (DLTZ) based on osmotic technology by using controlled porosity approach. DLTZ is an ideal candidate for a zero-order drug delivery system because it is freely water-soluble and has a short half-life (2-3 h). Sodium chloride (Osmogen) was added to the core tablet to alter the solubility of DLTZ in an aqueous medium. Cellulose acetate (CA) and sorbitol were used as semipermeable membrane and pore former, respectively. The effect of different formulation variables namely concentration of osmogen in the core tablet, % pore former, % weight gain, pH of the dissolution medium and agitation intensity on the in vitro release was studied. DLTZ release was directly proportional to % pore former and inversely proportional to % weight gain. The optimized formulation (F8) delivered DLTZ independent of pH and agitation intensity for 12 h at the upper level concentration of % pore former (25% w/w) and middle level concentration of % weight gain (6% w/w). The comparative study of elementary osmotic pump (EOP) and controlled porosity osmotic pump revealed that it superior than conventional EOP and also easier and cost effective to formulate.

Osmotic drug delivery system as a part of modified release dosage form

Conventional drug delivery systems are known to provide an immediate release of drug, in which one can not control the release of the drug and can not maintain effective concentration at the target site for longer time. Controlled drug delivery systems offer spatial control over the drug release. Osmotic pumps are most promising systems for controlled drug delivery. These systems are used for both oral administration and implantation. Osmotic pumps consist of an inner core containing drug and osmogens, coated with a semipermeable membrane. As the core absorbs water, it expands in volume, which pushes the drug solution out through the delivery ports. Osmotic pumps release drug at a rate that is independent of the pH and hydrodynamics of the dissolution medium. The historical development of osmotic systems includes development of the Rose-Nelson pump, the Higuchi-Leeper pumps, the Alzet and Osmet systems, the elementary osmotic pump, and the push-pull system. Recent advances include development of the controlled porosity osmotic pump, and systems based on asymmetric membranes. This paper highlights the principle of osmosis, materials used for fabrication of pumps, types of pumps, advantages, disadvantages, and marketed products of this system.

In situ formed phase transited drug delivery system of ketoprofen for achieving osmotic, controlled and level a in vitro in vivo correlation

A dry process induced phase transited, non disintegrating, controlled release, in situ formed asymmetric membrane capsular system for poorly water soluble drug, ketoprofen, was developed and evaluated both in vitro and in vivo for osmotic and controlled release of the drug. In situ formed asymmetric membrane capsules were prepared using fabricated glass capsule holders via dry, phase inversion process. Effect of varying osmotic pressure of the dissolution medium on drug release was studied. Membrane characterization by scanning electron microscopy showed an outer dense region with less pores and an inner porous region for the prepared asymmetric membrane. In vitro release studies and statistical test for all the prepared and marketed formulation were done at P >0.05. The drug release was found to be independent of the pH, but dependent on the osmotic pressure of the dissolution medium. In vivo pharmacokinetic studies showed a level A correlation (R²>0.99) with 39.24 % relative bioavailability compared to immediate release tablet of ketoprofen. Excellent correlation achieved suggested that the in vivo performance of the phase transited in situ formed AMCs could be accurately predicted from their in vitro release profiles and could a means for controlled delivery of drugs with varying solubility.

Materials for pharmaceutical dosage forms: molecular pharmaceutics and controlled release drug delivery aspects

Controlled release delivery is available for many routes of administration and offers many advantages (as microparticles and nanoparticles) over immediate release delivery. These advantages include reduced dosing frequency, better therapeutic control, fewer side effects, and, consequently, these dosage forms are well accepted by patients. Advances in polymer material science, particle engineering design, manufacture, and nanotechnology have led the way to the introduction of several marketed controlled release products and several more are in pre-clinical and clinical development.

Simultaneous delivery of Nifedipine and Metoprolol tartarate using sandwiched osmotic pump tablet system

The sandwiched osmotic tablet system that could deliver Nifedipine and Metoprolol tartarate simultaneously for extended period of time was developed in order to reduce the problems associated with multidrug therapy of hypertension. This system composed of a middle push layer and attached drug layers of Nifedipine and Metoprolol. The advantage of the sandwiched osmotic tablet system over the commercialized push-pull osmotic tablet system is its simplicity of preparation, as the surface identification was avoided. Polyethylene oxide 600,000 and 8,000,000 g/mole were used as thickening agent of drug layer and the expandable hydrogel of push layer, respectively. It has been observed that amount of polyethylene oxide (PEO) and KCL of the drug and push layer had profound influence on Nifedipine and Metoprolol release. Further, the release of drugs was optimized by the size of the delivery orifice, level of plasticizer and membrane thickness. The optimal osmotic pump tablet was found to deliver both drugs at a rate of approximately zero order for up to 16 h independent of pH and agitational intensity, but dependent on the osmotic pressure of the release media. The formulations were found to be stable after 3 months of accelerated stability studies. Prediction of steady-state levels showed the plasma concentrations of Nifedipine and Metoprolol to be within the desired range. Further sandwiched system had a good sustained effect in comparison with the conventional product. Hence the prototype design of the system could be applied to other combinations of drugs used for cardiovascular diseases, diabetes, etc.

Development and optimization of micro/nanoporous osmotic pump tablets

Micro/nanoporous osmotic pump tablets coated with cellulose acetate containing polyvinylpyrolidone (PVP) as pore formers were fabricated. Propranolol hydrochloride was used as a model drug in this study. Formulation optimization based on USP 31 requirements was conducted following a central composite design using a two-level factorial plan involving two membrane variables (pore former and coating levels). Effect of molecular weight of pore former (PVP K30 and PVP K90) was also evaluated. Responses of drug release to the variables were analyzed using statistical software (MINITAB 14). Scanning electron microscopy and atomic force microscopy showed that the pores formed by PVP. The drug release was dependent on the molecular weight and concentration of PVP and the level of coating. The results showed that acceptable 12-h profile could be achieved with only specific range of PVP K30-containing membrane at the defined membrane thickness. However, satisfactory 24-h profile could be accomplished by both PVP K30 and PVP K90-containing membrane at the range and membrane thickness tested. Preparation and testing of the optimized formulation showed a good correlation between predicted and observed values.

Oral osmotically driven systems: 30 years of development and clinical use

The number of marketed oral osmotically driven systems (OODS) has doubled in the last 10 years. The main clinical benefits of OODS are their ability to improve treatment tolerability and patient compliance. These advantages are mainly driven by the capacity to deliver drugs in a sustained manner, independent of the drug chemical properties, of the patient's physiological factors or concomitant food intake. However, access to these technologies has been restricted by the crowded patent landscape and manufacturing challenges. In this review article, we intend to give an overview of the OODS development in the last 30 years, detailing the technologies, specific products and their clinical use. General guidance on technology selection is described in light of the recent advances in the field. The clinical performance of these technologies is also discussed, with a focus on food effects and the in vivo-in vitro correlation. Special attention is paid to safety given the controversial case study of Osmosin. Overall, oral osmotically driven systems appear to be a promising technology for product life-cycle strategies.

Delivery of Prazosin Hydrochloride from Osmotic Pump System Prepared by Coating the Core Tablet with an Indentation

The preparation of an osmotic pump tablet was simplified by elimination of laser drilling using prazosin hydrochloride as the model drug. The osmotic pump system was obtained by coating the indented core tablet compressed by the punch with a needle. A multiple regression equation was achieved with the experimental data of core tablet formulations, and then the formulation was optimized. The influences of the indentation size of the core tablet, environmental media, and agitation rate on drug release profile were investigated. The optimal osmotic pump tablet was found to deliver prazosin hydrochloride at an approximately constant rate up to 24 hr, and independent on both release media and agitation rate. Indentation size of core tablet hardly affected drug release in the range of 0.80-1.15 mm. The method that is simplified by elimination of laser drilling may be promising for preparation of an osmotic pump tablet.

Solid Carriers for Improved Solubility of Glipizide in Osmotically Controlled Oral Drug Delivery System

The purpose of this study was to increase the solubility of glipizide (gli) by solid dispersions SDs technique with polyvinylpyrrolidone (PVP) in aqueous media. The gli-PVP solid dispersion systems was prepared by physical mixing or spray drying method, and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) analysis, Fourier transformation-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The elementary osmotic pumps (EOPs) were prepared with gli-PVP complex and the effect of the PVP percentages on the enhancing of gli dissolution rate was studied. The influences of various parameters e.g., drug- PVP ratio, level of solubility modifier, coating weight gain and diameter of drug releasing orifice on drug release profiles were also investigated. The solubility and dissolution rates of gli were significantly increased by solid dispersion using spray dried method as well as their physical mixture. The obtained results indicated that gli-PVP solid dispersion system has suitable solubility behavior in EOP tablets.

Statistical assessment of dissolution and drug release profile similarity using a model-dependent approach

A general multivariate procedure for assessing the similarity of dissolution and drug release profiles was developed. A mathematical model is fit to the data, and Hotelling's T(2) test is used to calculate the joint confidence region around the vector of differences between least-squares estimates of the parameters in the model. The method of Lagrange multipliers is used to determine if this confidence region is enclosed within a predetermined similarity region, and profile similarity is claimed if this is the case. The first-order, Gompertz, logistic, second-order, and Weibull models were fit to the in vitro extended-release profile of pseudoephedrine HCl from an asymmetric membrane (AM) film-coated osmotic tablet. The first-order model was selected because of its simplicity and because it was the best-fitting model according to a modified form of Akaike's Information Criterion. A nonlinear response surface model was also developed so that the formulator could calculate how much of the AM film coat should be applied in order to obtain the desired drug release profile. The usefulness of this model-dependent procedure was further demonstrated during an analytical method transfer exercise, where it was used to compare the drug release profiles obtained by two independent laboratories; additional research is required, however, before the appropriate acceptance criteria for demonstrating profile similarity can be recommended.

Osmotic flow through asymmetric membrane: a means for controlled delivery of drugs with varying solubility

A nondisintegrating, controlled release, asymmetric membrane capsular system of flurbiprofen was developed and evaluated for controlled release of the drug to overcome some of its side effects. Asymmetric membrane capsules were prepared using fabricated glass mold pins by phase inversion process. The effect of different formulation variables was studied based on 2(3) factorial design; namely, level of osmogen, membrane thickness, and level of pore former. Effects of polymer diffusibility and varying osmotic pressure on drug release were also studied. Membrane characterization by scanning electron microscopy showed an outer dense region with less pores and an inner porous region for the prepared asymmetric membrane. Differential scanning calorimetry studies showed no incompatibility between the drug and the excipients used in the study. In vitro release studies for all the prepared formulations were done (n = 6). Statistical test (Dunnett multiple comparison test) was applied for in vitro drug release at P > .05. The best formulation closely corresponded to the extra design checkpoint formulation by a similarity (f2) value of 92.94. The drug release was independent of pH but dependent on the osmotic pressure of the dissolution medium. The release kinetics followed the Higuchi model and the mechanism of release was Fickian diffusion.

An automated process for building reliable and optimal in vitro/in vivo correlation models based on Monte Carlo simulations

Many mathematical models have been proposed for establishing an in vitro/in vivo correlation (IVIVC). The traditional IVIVC model building process consists of 5 steps: deconvolution, model fitting, convolution, prediction error evaluation, and cross-validation. This is a time-consuming process and typically a few models at most are tested for any given data set. The objectives of this work were to (1) propose a statistical tool to screen models for further development of an IVIVC, (2) evaluate the performance of each model under different circumstances, and (3) investigate the effectiveness of common statistical model selection criteria for choosing IVIVC models. A computer program was developed to explore which model(s) would be most likely to work well with a random variation from the original formulation. The process used Monte Carlo simulation techniques to build IVIVC models. Data-based model selection criteria (Akaike Information Criteria [AIC], R2) and the probability of passing the Food and Drug Administration "prediction error" requirement was calculated. To illustrate this approach, several real data sets representing a broad range of release profiles are used to illustrate the process and to demonstrate the advantages of this automated process over the traditional approach. The Hixson-Crowell and Weibull models were often preferred over the linear. When evaluating whether a Level A IVIVC model was possible, the model selection criteria AIC generally selected the best model. We believe that the approach we proposed may be a rapid tool to determine which IVIVC model (if any) is the most applicable.

Drug-polymer mixed coating: a new approach for controlling drug release rates in pellets

A new approach to developing a drug-polymer mixed coat for highly water-soluble diltiazem pellets was investigated at different coating levels. Drug layering and the coating procedures were performed using a bottom spray fluidized bed coater. Drug pellets were coated with Eudragit NE40 (NE40) alone and in combination with diltiazem and hydrophilic cellulose derivatives. Dissolution studies revealed that incorporation of hydrophilic substances such as methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), and the drug itself considerably increased the release rates. The release from mixed polymer coatings was fast compared to pellets coated with NE40 only. The major portion of the drug was released in about 2 hours in case of MC and NE40 mixed coat compared to hours from coated pellets containing HPMC or diltiazem. Incorporation of 15% to 25% drug with respect to the polymer coat helped to achieve a drug-release profile at a desirable rate over a 12 hour period. Moreover, the test formulation comprising 25% diltiazem with respect to 7% NE40 had a dissolution profile that matched the commercial product, Herbesser SR capsules. The release of diltiazem from the coated pellets was slightly affected by the pH of dissolution media.

Applicability of (SBE)7m-beta-CD in controlled-porosity osmotic pump tablets (OPTs)

The purpose of this study was to investigate the general application of a controlled-porosity osmotic pump tablet (OPT) utilizing (SBE)7m-beta-CD as both a solubilizer and an osmotic agent for drugs with varying physical properties. OPTs utilizing (SBE)7m-beta-CD were prepared for five poorly soluble and two highly water-soluble drugs. The Japanese Pharmacopoeia dissolution method was used to study the drug and (SBE)7m-beta-CD release from the OPTs. The drug concentration in the OPT core after the OPT was placed in the release medium for two hours was assayed gravimetrically and by HPLC. An appropriate composition ratio (ACR) of (SBE)7m-beta-CD to drug at which drug release from the OPT was complete and pH-independent within the physiological pH range of the GI tract was determined for each drug. The ACR values correlate to the drug concentration in the OPT core when the OPTs were placed in the release medium for two hours. The release profiles of prednisolone (a poorly water-soluble drug) and sodium chloride (a water-soluble compound) from the OPTs were almost the same as that of (SBE)7m-beta-CD. Also, the release rate of each drug per unit membrane surface area from the OPTs was similar, regardless of the differences in drug solubility. The present results confirmed that (SBE)7m-beta-CD serves as both a solubility modulator and as an osmotic pumping agent for OPTs, from which the release rate of both water-soluble and poorly water-soluble drugs can be controlled.

Development and evaluation of osmotically controlled oral drug delivery system of glipizide

Extended release formulation of glipizide based on osmotic technology was developed and evaluated. The effect of different formulation variables, namely, level of solubility modifier in the core, membrane weight gain, and level of pore former in the membrane, were studied. Drug release was found to be affected by the level of solubility modifier in the core formulation. Glipizide release was inversely proportional to the membrane weight but directly related to the initial level of pore former (PVP) in the membrane. Burst strength of the exhausted shells increased with the weight gain of the membrane. On the other hand, burst strength decreased with an increase in the level of pore former in the membrane. Drug release from the developed formulations was independent of pH and agitational intensity, but dependent on the osmotic pressure of the release media. Results of SEM studies showed the formation of pores in the membrane from where the drug release occurred. The numbers of pores were directly proportional to the initial level of pore former in the membrane. The manufacturing procedure was found to be reproducible and formulations were stable after 3 months of accelerated stability studies.

Companion animal physiology and dosage form performance

Among the most critical parameters for any drug candidate are tolerability, dose, solubility and permeability. For controlled release formulations, gastrointestinal transit is an added hurdle. While we might assume that intestinal transit is independent of the drug candidate, the relative importance of gastrointestinal transit time (GITT) depends directly on the other parameters. For example, a formulation of a drug with low solubility (LS) and/or low permeability (LP) characteristics might provide the required systemic concentrations when administered with food, but not if administered on an empty stomach. In the LS case, the drug may require the solubilizing effects of increased fluid and bile salts that accompany the meal. Likewise, a controlled release formulation of a drug with a region of preferred absorption may empty from the fasted stomach and move beyond the region before drug release is complete. Companion animals (e.g. cats and dogs) differ from humans and each other with respect to GITT, food effects, eating habit influences, breed and size variability, gastric pH, intestinal enzymes, GI permeability and absorption regions. This review examines how the anatomy and physiology of companion animals relates to the performance of orally administered immediate and controlled release formulations. Examples are presented of techniques used to predict the dose and acceptable solubility of drug candidates, and the performance of formulations in companion animals.

Controlled Porosity Osmotic Pumps of Highly Aqueous Soluble Drug Containing Hydrophilic Polymers as Release Retardants

Controlled porosity osmotic pumps (CPOPs) are devoid of delivery orifice to release core contents and essentially possess pore-forming agent(s) in coating composition. When the pump comes in contact with aqueous media, pore-forming agent(s) generate pores through which core contents are delivered. Diltiazem hydrochloride (DLTZ) is a freely water-soluble drug and the release rates of DLTZ are higher from oral osmotic pumps including CPOPs, in which the drug release is controlled by concentration of pore-forming agents. The effect of appropriate concentration of hydroxypropyl methyl cellulose and sodium carboxy methyl cellulose mixture on the release of DLTZ from CPOPs was studied. In vitro drug release profiles were compared with that of different marketed controlled release formulations and statistically analysed to examine the suitability of CPOP for twice or once daily administration. Dissolution models were applied to drug release data in order to establish the mechanism of drug release and kinetics. Drug release from the CPOPs was effectively modified with the concentration of pore-forming agent in membrane and concentration of hydrophilic polymers in the core. CPOPs showed minimum 65% of consistent DLTZ release at 16 h. Statistical analysis confirmed that with an increase in the amount of hydrophilic polymers release rate decreased. Drug release from the systems follows Hixson-Crowell cube root model and mechanism of release follow non-Fickian diffusion.

Investigation of cyclobenzaprine hydrochloride release from oral osmotic delivery systems containing a water-swellable polymer

Oral osmotic delivery systems containing polyethylene oxide (PEO, a water-swellable polymer) were designed and the release of cyclobenzaprine hydrochloride (model drug) from the devices was investigated. The systems consisted of model drug, mannitol (osmotic agent), and increasing amounts of PEO surrounded by a semipermeable membrane drilled with a delivery orifice. There was a decrease in drug release rate with PEO in the core. This may be due to solubility-modulating properties of the polymer. Visual inspection of the devices with PEO showed significant swelling during dissolution testing. Swelling (internal pressure) may influence water inhibition rate into the core and subsequently drug release rate. The release rates were a function of membrane thickness. The release rates were independent of orifice size (range of 150-510 microns diameter) and hydrodynamic conditions for the devices. This would be advantageous in the delivery of drugs in man.

Preparation and characterization of a customized cellulose acetate butyrate dispersion for controlled drug delivery

The purpose of the present experiment was to prepare and characterize the aqueous-based pseudolatex system of cellulose acetate butyrate (CAB) for controlled drug delivery. Aqueous pseudolatex systems are advantageous over organic-based coating systems because these systems are devoid of criteria pollutants such as carbon monoxide, nitrogen oxides, nonmethane volatile organic compounds, and sulfur dioxide. Pseudolatex was prepared with CAB and polyvinyl alcohol (stabilizer) by a polymer emulsification technique. The stability of pseudolatex was evaluated. Particle size was measured and rheological experiments were conducted. The glass transition temperature, microscopic free volume, permeation coefficient, and mechanical properties of plasticized pseudolatex films were estimated. Surface roughness of coating on inert Nu-Pareil beads (Ingredient Technology Corp., Mahwah, NJ) was measured as a function of coating weight gain. The CAB Pseudolatex was found to be stabilized by steric forces. From intrinsic viscosity, the thickness of the stabilization layer was estimated. An increase in polymeric particles proportionately decreased the thickness of the stabilization layer. All the essential properties of a coating membrane such as microscopic free-volume fraction, permeability coefficient, mechanical properties, and glass transition temperature were fairly controllable as a function of plasticizer concentration. The pseudolatex dispersion of CAB was stable with negligible sedimentation volume and a particle size of 300 nm. Because CAB is water insoluble and non-ionizable, this pseudolatex can be used for pH-independent coating. The films obtained were strong and flexible for controlled drug delivery applications. Coating with the CAB dispersion reduced the surface roughness of beads but it remained stable as a function of increase in coating weight gain.

Influence of plasticization time, curing conditions, storage time, and core properties on the drug release from Aquacoat-coated pellets

Theophylline or chlorpheniramine maleate pellets were coated with an aqueous ethylcellulose dispersion, Aquacoat. The influence of the plasticization time, curing conditions, storage time, and core properties on the drug release were investigated. The plasticization time (time between plasticizer addition to the polymer dispersion and the spraying process) did not affect the drug release, when the water-soluble plasticizer triethyl citrate, was used because of its rapid uptake by the colloidal polymer particles. In contrast, with the water-insoluble plasticizer acetyltributyl citrate (ATBC), plasticization time (1/2 h vs 24 h) influenced the drug release, the longer plasticization time resulted in a slower drug release because of a more complete plasticizer uptake prior to the coating step. However a thermal aftertreatment of the coated pellets at eleylated temperatures (curing step) reduced/eliminated the effect of the plasticization time with ATBC. In general, curing reduced the drug release and resulted in stable drug release profiles. The time period between the coating and the curing step was not critical when the pellets were cured for a longer time. The structure of the pellet core (high dose matrix vs low dose layered pellet) strongly affected the drug release. A slow, zero-order drug release was obtained with high dose theophylline pellets, while a more rapid, first-order release pattern was obtained with low dose theophylline-layered nonpareil pellets.

Osmotically controlled oral drug delivery

It is advantageous to deliver some drugs with short half-life, and which are to be given frequently for chronic ailments, in the form of controlled-release (CR) formulations. The orally administered drugs, in the form of conventional matrix or reservoir type formulations, pose problems of bioavailability fluctuations due to gastric pH variations. Moreover, the release of drug(s) from these systems is affected by the hydrodynamic conditions of the body. Osmotically controlled drug delivery systems utilize the principles of osmotic pressure for the controlled delivery of active agent(s). The release rate of drug(s) from these systems is independent of the physiological factors of the gastrointestinal (GI) tract to a large extent. In the present review, theory underlying the delivery of drugs from osmotic systems is presented. Different types of oral osmotic systems, their advantages over conventional matrix and reservoir types of systems, and their applications are also discussed. Finally, some of the limitations, adverse effects, and patent and market status of these systems are reviewed. These systems form a major segment of drug delivery products. Because of their advantages and strong market potential, it appears that the future of osmotic systems in rate-controlled oral drug delivery is promising.

In situ electrolyte interactions in a disk-compressed configuration system for up-curving and constant drug delivery

A new approach in drug delivery system design for meeting the needs that are associated with certain circadian variations is presented. The system is comprised of a pure compressed drug disk, which is encased by a polymeric coat using hydroxypropylmethylcellulose or polyethylene oxide. Within the polymeric coat, a physiologically acceptable binary electrolyte combination such as sodium deoxycholate and adipic acid is disposed. Through this process and upon exposure to dissolution media, ionic interactions occur and a texturally variable matrix is manifested in the form of peripheral stiffening' with self-correcting boundaries as demonstrated by texture analysis studies. The peripheral boundaries erode and progressively shift toward the disk-core, thus constantly reducing the diffusional pathlength with the resultant up-curving kinetics. Utilizing these mechanisms, a lag time is induced and drug is delivered over a 24-h period in one of two ways namely, in an up-curving or constant manner for drug models theophylline and diltiazem hydrochloride with water solubilities of 0.85% and > 50% at 25 degrees C, respectively. It appears that for both sparingly and highly soluble drugs, sum of the dissolution/diffusion rates, dynamics of diffusional pathlength and system erosion rate control the release process. The heterogeneous nature of changes in coat thickness, stiffening dynamics and erosion rate in relation to disk geometry is discussed. The developed technology has potential to provide release patterns, compatible with specific chronophysiological conditions, and overcome the absorption-limited capacity of the distal gastrointestinal tract

An approach to controlled-release dosage form of propranolol hydrochloride

It is possible to release a drug with only limited diffusion from a membrane-coated system using osmotic pumping. In this study, a propranolol osmotic pump was produced by coating the core tablets with cellulose acetate. The effects of membrane thickness, pore size, and stirring rate on the release rate of propranolol hydrochloride were studied. It was found that the thickness of cellulose acetate membrane had a profound effect on the release rate of propranolol hydrochloride from the membrane-coated tablets. The results showed that, when the membrane thickness increased, the release rate of propranolol decreased. The drug release follows a zero-order release when the delivery orifice is between 200 and 800 microns, but when the delivery orifice size is increased to 1000 microns, the release kinetic is abnormal. Fluid dynamics have an important effect on the delivery rate of propranolol from this device; the delivery rate increases as a function of the fluid flow. The drug release is higher under a turbulent condition with high rate of stirring.

Electrolyte-induced compositional heterogeneity: a novel approach for rate-controlled oral drug delivery

In this work a new approach for in situ interactions between drug and electrolyte(s) is devised to control the release of highly water soluble drugs from oral hydrophilic monolithic systems. The model drug diltiazem hydrochloride (water solubility in excess of 50% at 25 degrees C), in conjunction with specific electrolytes, was principally employed in the design of swellable tablet formulations comprised of hydrophilic polymers such as hydroxypropylmethlcellulose (HPMC) or poly(ethylene oxide) (PEO). Electrolytes such as sodium bicarbonate or pentasodium tripolyphosphate were used to modulate intragel pH dynamics, swelling kinetics, and gel properties. Through in situ ionic interactions (an intragel matrix system composed of different chemical species that promote competition for water of hydration), a compositionally heterogeneous structure referred to as a "metamorphic scaffold" was established. It is shown that this latter structure results in the inhibition of drug dissolution, induction of a differential swelling rate, and attainment of "matrix stiffening" and axially provides a uniform gel layer. Presence of such phases in matrix structure and its influence on swelling dynamics enabled control of diltiazem hydrochloride release in a zero-order manner in different pH environments over a 24-h period. From kinetic analysis using the power law expressions [M(t)/M(infinity) = k(1)t(n), M(t)/M(infinity) = k(1)t(n) + k(2)t(2)(n)] and Hopfenberg model [M(t)/M(infinity) = 1 - (1 - k(1)t)(n)], it became apparent that the dynamics of matrix relaxation and controlled erosion were major factors involved in the release mechanism, while the composite rate constant k(1) (in Hopfenberg model) decreased by approximately 2-fold in the presence of electrolyte(s). These findings indicated that the dynamics of swelling and gel formation in the presence of ionizable species within hydrophilic matrices provide an attractive alternative for zero-order drug delivery from a simple monolithic system.

Factors affecting membrane-controlled drug release for an osmotic pump tablet (OPT) utilizing (SBE)(7m)-beta-CD as both a solubilizer and osmotic agent

PURPOSE

The purpose of this study was to define membrane controlling factors responsible for drug release from a controlled-porosity osmotic pump tablet (OPT) that utilizes a sulfobutyl ether-beta-cyclodextrin, (SBE)(7m)-beta-CD, as both a solubilizing and osmotic agent.

METHOD

The OPT was spray coated with cellulose acetate solutions varying the amount and size of micronized lactose, the amount of triethyl citrate (TEC) and the composition ratio of dichlormethane to ethanol. Chlorpromazine (CLP) was used as a model drug. The release of CLP from the OPTs was studied using the Japanese Pharmacopoeia dissolution method. The membrane surface area of the OPTs were measured with multi-point analysis by the gas absorption method.

RESULTS

The release rate of CLP from OPTs containing (SBE)(7m)-beta-CD increased with increasing amounts of micronized lactose and decreasing amounts of TEC and lactose particle size in the membrane. Also, the CLP release rates from the spray-coated OPTs using mixtures of varying ratios of dichlormethane to ethanol were almost identical. The membrane surface area of the OPTs following release of membrane components had a linear relationship to CLP release rates from the OPTs.

CONCLUSION

The present results confirmed that the membrane controlling factors responsible for the drug release were the amount and size of micronized lactose and the amount of TEC in the membrane.

Release of testosterone from an osmotic pump tablet utilizing (SBE)7m-beta-cyclodextrin as both a solubilizing and an osmotic pump agent

A controlled porosity osmotic pump system for poorly water soluble drugs has been developed using sulfobutyl ether-beta-cyclodextrin sodium salt, (SBE)7m-beta-CD, which can act as both a solubilizing and an osmotic agent. The release of testosterone, a poorly water soluble drug (0.039 mg/ml at 37 degrees C), was evaluated using a new model device. The effect of (SBE)7m-beta-CD as the solubilizing and osmotic pump agent was compared with hydroxypropyl-beta-cyclodextrin (HP-beta-CD), a neutral cyclodextrin, and a sugar mixture (osmotic agent only). Testosterone release from the device was significantly faster with (SBE)7m-beta-CD than with HP-beta-CD or the sugar mixture. The solubility of testosterone in the device increased to 76.7 mg/ml through complexation with (SBE)7m-beta-CD in the imbibed water. It appears that testosterone release from the device in the presence of (SBE)7m-beta-CD was mainly due to osmotic pumping while for HP-beta-CD the major contribution appears to be due to diffusion. In the case of the sugar mixture, testosterone was poorly released, presumably due to the absence of a solubilizer. Therefore, it was concluded that (SBE)7m-beta-CD provides novel properties for the development of controlled- porosity osmotic pump tablets for poor solubility drugs.

Design and evaluation of an osmotic pump tablet (OPT) for prednisolone, a poorly water soluble drug, using (SBE)7m-beta-CD

PURPOSE

The purpose of this study was to develop a controlled-porosity osmotic pump tablet (OPT) for poorly water soluble drugs using a sulfobutyl ether-beta-cyclodextrin, (SBE)7m-beta-CD or Captisol, which acted as both a solubilizer and as an osmotic agent.

METHODS

Prednisolone (PDL) was chosen as a model drug for this study. The release of PDL from osmotic pump devices and tablets was studied. In vivo absorption of PDL from OPT was evaluated in male beagle dogs.

RESULTS

PDL release from the osmotic pump tablet with (SBE)7m-beta-CD was complete. Another cyclodextrin, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and a sugar mixture of lactose and fructose resulted in incomplete release. Although PDL release from the OPT with (SBE)7m-beta-CD and the sugar formulation displayed mainly zero-order release characteristics, the tablet utilizing HP-beta-CD showed apparent first-order release characteristics. An in vivo absorption study in dogs correlated very well with the in vitro release profiles using the Japanese Pharmacopoeia dissolution method.

CONCLUSIONS

The present results confirm that (SBE)7m-gamma-CD can serve as both the solubilizer and the osmotic agent for OPT of PDL, and modify the input rate of PDL without compromising oral bioavailability.

Guar gum-based sustained release diltiazem

PURPOSE

This study was performed to examine the use of guar gum to sustain the release of diltiazem under in vitro and in vivo conditions.

METHODS

Guar gum tablet formulations were prepared and evaluated under a variety of in vitro dissolution conditions. The formulations, along with Dilacor XR, were administered to a group eight fasted, healthy volunteers in a four period crossover study.

RESULTS

Varying the lot of guar gum as well as using guar from different suppliers had little effect on diltiazem dissolution. Also, dissolution of diltiazem from guar gum tablets was essentially independent of stir speed under normal conditions (USP Apparatus II) The stability of guar-based formulations under stressed conditions (40 degrees C/75% relative humidity for 3 months) was also established. All four formulations gave similar plasma concentrations over time in the healthy volunteers pharmacokinetic study.

CONCLUSIONS

Guar gum-based matrix tablets represent a simple and economical alternative to existing diltiazem sustained release dosage forms.

The influence of buffer species and strength on diltiazem HCl release from beads coated with the aqueous cationic polymer dispersions, Eudragit RS, RL 30D

PURPOSE

Eudragit RL and RS 30D are pseudolatexes frequently used in the coating of solid dosage forms. They are based on cationic copolymers stabilized with quaternary ammonium groups (poly(ethylacrylate-methylmethacrylate-trimethylammonioethyl methacrylate chloride). A pH-independent drug release is expected because of the quaternary nature of the cationic groups. The objective was to explain a distinct "pH-dependent" drug release in various buffer media with coated diltiazem beads.

METHODS

The diltiazem HCl release from and water uptake of Eudragit RS/RL-coated beads was determined in various buffers of different buffer species, pH or concentration.

RESULTS

The drug release in the different buffer media was in the following order: pH 5.0 acetate > pH 3.5 formate > pH 7.4 phosphate buffer > 0.1M HCl). This "pH-dependent" drug release could be explained with an anion exchange process; the chloride counterions of the quaternary groups were exchanged with the anionic buffer species during the dissolution study. The water uptake of the coated beads correlated well with the drug release from the beads. Increasing the buffer strength (acetate buffer) first increased and then decreased the drug release, while increasing the ionic strength of different buffers with NaCl decreased the drug release and eliminated the observed buffer effects because of the excess of chloride ions.

CONCLUSIONS

The anionic buffer species and not the pH had a significant effect on the hydration and hence on the drug release from beads coated with the cationic polymers, Eudragit RS and RL.

Use of modified ethylcellulose lattices for microporous coating of osmotic tablets

Commercially available lattices are often used to coat nonpareils or beads. Drug release occurs via diffusion through the polymer coating. Adequate release rates may be achieved with small particles because the surface area is large. However, tablets coated with unmodified lattices have exceedingly slow release rates. Therefore, a pore-forming agent, urea, was added to a commercially available ethyl cellulose latex, Aquacoat, to increase the release rate of drugs from coated osmotic tablets. Modified lattices were used to coat KCl and diltiazem.HCl tablets. Release of KCl and diltiazem into water or buffer solutions was determined in a standard U.S.P. dissolution apparatus. Rates varying from 1 to 100% release in 12 hr were obtained by varying the coating thickness, pore-former level, and plasticizer type and concentration. Scanning electron microscopy (SEM) showed that the urea was eluted from the coat in aqueous solution leaving a porous coating. Coat burst strengths were dependent on the coat thickness and the concentrations of pore former and plasticizer. Hence, modified lattices hold potential for use as coatings for controlled release osmotic formulations.