Alekha K. Dash

Therapeutic applications of implantable drug delivery systems

In the past, drugs were frequently administered orally, as liquids or in powder forms. To avoid problems incurred through the utilization of the oral route of drug administration, new dosage forms containing the drug(s) were introduced. As time progressed, there was a need for delivery systems that could maintain a steady release of drug to the specific site of action. Therefore, drug delivery systems were developed to optimize the therapeutic properties of drug products and render them more safe, effective, and reliable. Implantable drug delivery systems (IDDS) are an example of such systems available for therapeutic use. The application of currently available implantable drug delivery systems is the main focus of this review. IDDS can be classified into three major categories: biodegradable or nonbiodegradable implants, implantable pump systems, and the newest atypical class of implants. Biodegradable and nonbiodegradable implants are available as monolithic systems or reservoir systems. The release kinetics of drugs from such systems depend on both the solubility and diffusion coefficient of the drug in the polymer, the drug load, as well as the in vivo degradation rate of the polymer, especially, in the case of the biodegradable systems. Controlled release of drug from the implantable pump is generally achieved utilizing the microtechnology of electronic systems and remote-controlled flow rate manipulation through the maintenance of a constant pressure difference. The third atypical class includes those which have been recently developed such as ceramic hydroxyapatite antibiotic systems used in the treatment of bone infections, intraocular implants for the treatment of glaucoma, and transurethral implants utilized in the treatment of impotence. The major advantages of these systems include targeted local delivery of drugs at a constant rate, less drug required to treat the disease state, minimization of possible side effects, and enhanced efficacy of treatment. Also, these forms of delivery systems are capable of protecting drugs which are unstable in vivo and that would normally require a frequent dosing intervals. Due to the development of such sustained release formulations, it is now possible to administer unstable drugs once a week to once a year that in the past required frequent daily dosing. Preliminary studies using these systems have shown superior effectiveness over conventional methods of treatment. However, one limitation of these newly developed drug delivery systems is the fact that their cost-to-benefit ratio (cost/benefit) is too high which restricts their use over conventional dosage forms. Hopefully, in the future, new implantable systems can be developed at a lower cost, thereby minimizing the cost-to-benefit ratio and therefore, be used extensively in standard therapeutic practice. Some of the most recently discovered implants are in the early developmental stages and more rigorous clinical testing is required prior to their use in standard practice.

Combination antiretroviral drugs in PLGA nanoparticle for HIV-1

BackgroundCombination antiretroviral (AR) therapy continues to be the mainstay for HIV treatment. However, antiretroviral drug nonadherence can lead to the development of resistance and treatment failure. We have designed nanoparticles (NP) that contain three AR drugs and characterized the size, shape, and surface charge. Additionally, we investigated the in vitro release of the AR drugs from the NP using peripheral blood mononuclear cells (PBMCs).MethodsPoly-(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) containing ritonavir (RTV), lopinavir (LPV), and efavirenz (EFV) were fabricated using multiple emulsion-solvent evaporation procedure. The nanoparticles were characterized by electron microscopy and zeta potential for size, shape, and charge. The intracellular concentration of AR drugs was determined over 28 days from NPs incubated with PBMCs. Macrophages were imaged by fluorescent microscopy and flow cytometry after incubation with fluorescent NPs. Finally, macrophage cytotoxicity was determined by MTT assay.ResultsNanoparticle size averaged 262 ± 83.9 nm and zeta potential -11.4 ± 2.4. AR loading averaged 4% (w/v). Antiretroviral drug levels were determined in PBMCs after 100 μg of NP in 75 μL PBS was added to media. Intracellular peak AR levels from NPs (day 4) were RTV 2.5 ± 1.1; LPV 4.1 ± 2.0; and EFV 10.6 ± 2.7 μg and continued until day 28 (all AR ≥ 0.9 μg). Free drugs (25 μg of each drug in 25 μL ethanol) added to PBMCs served as control were eliminated by 2 days. Fluorescence microscopy and flow cytometry demonstrated phagocytosis of NP into monocytes-derived macrophages (MDMs). Cellular MTT assay performed on MDMs demonstrated that NPs are not significantly cytotoxic.ConclusionThese results demonstrated AR NPs could be fabricated containing three antiretroviral drugs (RTV, LPV, EFV). Sustained release of AR from PLGA NP show high drug levels in PBMCs until day 28 without cytotoxicity.

SYNTHESIS AND CHARACTERIZATION OF HYDROXYAPATITE-CIPROFLOXACIN DELIVERY SYSTEMS BY PRECIPITATION AND SPRAY DRYING TECHNIQUE

This investigation synthesized and characterized hydroxyapatite (HAP) microspheres, agglomerated microspheres, and implants containing ciprofloxacin. This delivery system is to be used as an implantable drug delivery system for the treatment of bone infections. The HAP microspheres were made by chemical precipitation followed by a spray-drying technique. Agglomerated microspheres were prepared by a wet granulation process using a granulator. Implants were prepared by direct compression of the granules on a Carver press. Ciprofloxacin was analyzed by high-performance liquid chromatography. Characterization of the HAP microspheres include particle size, size distribution, physical state of the drug in the microsphere, and microstructure of the drug delivery system before and after in vitro release. The particle size, porosity, and morphology of the microspheres were dependent on viscosity and concentration of the slurry as well as the atomization pressure used during spray drying. Even at the highest drug load (2% wt/wt), the drug was present in a noncrystalline state. The drug release from the agglomerated microspheres was quick and almost complete within 1 hour. However, compressing the same amount of agglomerated microspheres into an implant greatly reduced the rate of ciprofloxacin release. Only 12% (wt/wt) of the drug was released from the implant within 1 hour.The in vitro release of ciprofloxacin from these implants follows a diffusion-controlled mechanism. This method provides a unique way of producing various shapes and drug loads of HAP microspheres that can be easily manufactured on a commercial scale.

Effect of cross-linking on the in vitro release kinetics of doxorubicin from gelatin implants

Doxorubicin is one of the most potent anti-tumor agents used generally in the treatment of bone cancer. Like other cancer chemotharepeutics, it produces undesirable side effects such as cardiotoxicity, which is especially severe when administrated via the conventional intravenous route. In order to minimize the systemic toxicities and to make this drug more suitable for the treatment of bone cancer, an implantable delivery system with cross-linked gelatin as the biodegradable matrix material was developed. This delivery system could possibly improve targeting of the drug as well as sustain the rate of release of the drug to the tumor. Glutaraldehyde was used as a cross-linking agent. Incorporation of glutaraldehyde in the matrix was needed to maintain the mechanical strength of the implant and to sustain the rate of release of the drug from the implant. Besides cross-linking the gelatin matrix, glutaraldehyde was found to cross-link the free amino group of doxorubicin. The effect of cross-linker concentration on the stability of the drug in the implant and on the rate and extent of release were also evaluated. In conclusion, cross-linked gelatin implants were developed for the local delivery of doxorubicin.

Evaluation of red cabbage dye as a potential natural color for pharmaceutical use

Red cabbage dye is a natural pigment used mainly as a food color. A class of compounds called anthocyanins attributes to this color. The pH of the red cabbage solution can also affect both its color and intensity. The objective of this study was to determine the ionization constant (pK(a)) of red cabbage color, the effect of pH and temperature on its stability in solution and evaluation of this natural color as a pH indicator in pharmaceutical system. Spectrophotometric method was used to determine its pK(a). The lambda(max) and absorbencies of the red cabbage color at different concentrations and pH were determined. The analytical wavelength (AW) is the wavelength at which the greatest difference in absorbencies between ionized and molecular species occurs was determined. The absorbencies of red cabbage solution (0.12% w/v) at different pH values ranging from 5.0 to 8.0 (with increments of 0.2), was measured at the AW of 612 nm. The resulted absorbencies ranged from 0.31 to 1.91 and were used to determine its pK(a). The pK(a) determined by this method was within a range of 6.8-7.2. Results from this study demonstrated that red cabbage dye could be used as a pH indicator in pharmaceutical formulations. In acidic condition, it has its original red color but at a basic pH its color changes to deep blue. This color is more stable at a low temperature and pH. Its ability to act as a pH indicator was further tested using chlorbutol solution as a model system.

A simple LC method with UV detection for the analysis of creatine and creatinine and its application to several creatine formulations

The objective of this study was to develop a simple and sensitive LC method for the determination of creatine and creatinine in various creatine supplement formulations. The chromatographic system comprised of a LC-600 pump, SCL-6B system controller, and SPD-6AV detector (Shimadzu, Japan). The mobile phase consisted of 0.045 M ammonium sulfate in water. The chromatographic separation was achieved at ambient temperature on a Betabasic C-18 column (250 x 4.6 mm, Keystone Sci.). The flow rate was maintained at 0.75 ml/min and effluents are monitored at 205 nm. 4-(2-Aminoethyl)benzene sulfonamide was used as an internal standard (IS). This method required less than 7 min of chromatographic time. The standard curves were linear over the concentration range of 1-100 microg/ml for creatine and 2-100 microg/ml for creatinine, respectively. The relative standard deviations (RSD) for the within-day and day-to-day precision for creatine were within 1.0-4.6 and 2.2-4.7%, respectively. The RSD for the accuracy of creatine assay was in the range of 2.4-4.7%. The RSD values for the within-day precision, day-to-day precision and accuracy for creatinine validation were 1.7-4.4, 2.3-5.4 and 2.4-4.8%, respectively. This method was used to determine: (i) the creatine concentration in various marketed products; (ii) saturated solubility of various creatine salts; and (iii) stability of creatine in aqueous solution. In conclusion, a simple and sensitive LC method with UV detection was developed for the simultaneous determination of creatine and creatinine in formulations. Di-creatine citrate salt showed a higher aqueous solubility (at 25 degrees C) as compared to creatine and creatine monohydrate. Some of the over-the-counter (OTC) products tested contained a very low level of creatine in contrast to their label claim. Substantial conversion of creatine into creatinine was noticed in liquid formulation.

Development of a rectal nicotine delivery system for the treatment of ulcerative colitis.

The aims of this investigation were: i. to develop a rectal nicotine delivery system with bioadhesives for the treatment of ulcerative colitis and ii. to evaluate nicotine transport and cytotoxicity of the delivery system using Caco-2 cell culture systems. Rectal nicotine suppository formulations were prepared in semi-synthetic glyceride bases (Suppocire AM and AI, Gattefosse Inc.) by fusion method. The in vitro release of nicotine was carried out in modified USP dissolution apparatus 1. Differential scanning calorimetry (DSC) and powder X-ray diffraction were used to study the polymorphic changes if any in the formulations. An LC method was used for the assay of nicotine. The effect of bioadhesives (glyceryl monooleate (GMO), and Carbopol) on the nicotine flux was evaluated using Caco-2 cell permeability studies and Caco-2 cell viability was determined using the MTT toxicity assay. In vitro release studies indicated that the low melting AI base was superior to that of the AM base. Presence of GMO in the formulation enhanced the release of nicotine whereas Carbopol showed an opposite effect. The enhanced release of nicotine in the presence of GMO was found to be partly due to the melting point lowering effect of this compound. Caco-2 cell absorption studies showed that there was a decrease in the flux of nicotine in the presence of both the bioadhesives. The flux of the fluorescein marker which is used to study the integrity of the cell monolayers was found to be slightly higher only in the presence of 10% (w/w) Carbopol. Nicotine, Carbopol, and GMO do not have any cytotoxic effect on these cell monolayers within the concentration range used in the formulations. Rectal nicotine formulations containing bioadhesives were developed and characterized. Both in vitro release and cell culture studies have indicated that one can manipulate the nicotine release from these rectal delivery systems by incorporation of various bioadhesives or the use of different bases in the formulation. Nicotine concentration below 2% (w/v) and bioadhesive concentration below 10% (w/w) do not have any cytotoxic effect on Caco-2 cells.

A mucoadhesive in situ gel delivery system for paclitaxel

MUC1 gene encodes a transmembrane mucin glycoprotein that is overexpressed in human breast cancer and colon cancer. The objective of this study was to develop an in situ gel delivery system containing paclitaxel (PTX) and mucoadhesives for sustained and targeted delivery of anticancer drugs. The delivery system consisted of chitosan and glyceryl monooleate (GMO) in 0.33M citric acid containing PTX. The in vitro release of PTX from the gel was performed in presence and absence of Tween 80 at drug loads of 0.18%, 0.30%, and 0.54% (wt/wt), in Sorensen’s phosphate buffer (pH 7.4) at 37°C. Different mucin-producing cell lines (Calu-3>Caco-2) were selected for PTX transport studies. Transport of PTX from solution and gel delivery system was performed in side by side diffusion chambers from apical to basal (A-B) and basal to apical (B-A) directions. In vitro release studies revealed that within 4 hours, only 7.61%±0.19%, 12.0%±0.98%, 31.7%±0.40% of PTX were released from 0.18%, 0.30%, and 0.54% drugloaded gel formulation, respectively, in absence of Tween 80. However, in presence of surfactant (0.05% wt/vol) in the dissolution medium, percentages of PTX released were 28.1%±4.35%, 44.2%±6.35%, and 97.1%±1.22%, respectively. Paclitaxel has shown a polarized transport in all the cell monolayers with B-A transport 2 to 4 times higher than in the A-B direction. The highest mucin-producing cell line (Calu-3) has shown the lowest percentage of PTX transport from gels as compared with Caco-2 cells. Transport of PTX from mucoadhesive gels was shown to be influenced by the mucin-producing capability of cell.

Liquid chromatographic method for the determination of nicotine in pharmaceutical formulations

A simple high-performance liquid chromatography method was developed and validated for the analysis of nicotine in various pharmaceutical formulations. This method required a simple liquid-liquid extraction procedure prior to liquid chromatography analysis. The chromatographic separation was achieved on a reversed-phase C18 column with ultraviolet detection at 260 nm. This isocratic system was operated at ambient temperature and required 10 min of chromatographic time. The mobile phase consisted of methanol-citrate phosphate buffer (15:85, v/v) at a flow-rate of 0.7 ml/min. Standard curves were linear over the concentration range 1.0–51 μg/ml. Within-day and day-to-day relative standard deviations ranged from 1.3 to 4.4% and from 2.4 to 4.2%, respectively.

An Implantable Dosage Form for the Treatment of Bone Infections

The object of this investigation was the development of an implantable sustained-release dosage form, for the treatment of bone infections. Cross-linked polydimethylsiloxane (PDMS) was used as the matrix material. The drug delivery system was prepared by incorporating tobramycin, as a free base (C18H37N5O9 · H2O) or as a sulfate salt [(C18H37N5O9)2 · 5H2SO4], into the matrix and molding into spherical beads. Following in vitro studies, the cumulative amount of drug released when plotted as a function of the square root of time was linear for both the base and the salt. The addition of glycerol to the matrix substantially accelerated the rate of drug release and the plots of cumulative amount of drug released continued to be linear as a function of the square root of time. The glycerol-incorporated beads swelled in contact with the aqueous medium but a negligible amount of glycerol was released even after exposure to the medium for 20 days. 13C solid-state and high-resolution NMR studies indicated that a fraction of the added glycerol participated in the cross-linking reaction of the polymer. The effect of the initial molecular weight of PDMS and the effect of the concentration of the cross-linker on the kinetics of drug release were investigated.