Current Drug Delivery - Volume 8, Issue 5, 2011

The aim of the current study was to develop osmotically controlled release system of freely water soluble drug phenylephrine hydrochloride by use of asymmetric membrane capsules to reduce the dosing frequency and consequently improve the patient compliance. Ethyl cellulose asymmetric membrane capsules were developed by phase inversion process and solubility modulation was accomplished by common ion effect wherein sodium chloride was included in the formulation that also served as an osmogen. The effect of formulation variables namely level of polymer (ethyl cellulose), level of pore former (glycerol) and level of osmogen (sodium chloride) on the in vitro release of the drug was evaluated by 23 factorial design. Effects of environmental factors on the release rate of the drug from asymmetric membrane capsules were also evaluated. Membrane characterization by scanning electron microscopy showed an outer dense region with less pores and inner porous region for the prepared asymmetric membrane. The dimensional analysis of asymmetric membrane capsule documented the capsules to be of uniform cap and body size comparable to commercial hard gelatin capsules. In vitro release studies results showed that incorporation of higher amount of osmogen not only increased the osmotic pressure but also controlled the drug release for a period of 12 hr. The drug release was inversely proportional to the level of polymer in asymmetric membrane capsule but directly related to the level of pore former in the membrane. The optimized asymmetric membrane capsule (F5) was able to provide zero order release of phenylephrine hydrochloride independent of agitation rate, intentional defect in the membrane and pH of dissolution medium but was dependent on the osmotic pressure gradient between inside and outside of the delivery system.

Depression is a common mental disorder discerns with depressed mood, loss of interest, the primary treatment methods are drug therapy, electroconvulsive therapy, psychotherapy, light therapy, vagus nerve stimulation, etc. A number of innovative delivery systems have been developed to address suboptimal therapy outcomes by enhancing drug delivery, assuring efficacy of treatment, reducing side effects, improving compliance and drug targeting specific locations resulting in a higher efficiency. Depot delivery offers the advantage of a very high loading, controlled release of drug for an extended period of time and reduces frequency of dosing. The increase in AUC and decrease in Cmax reflects that the depot formulations could reduce the toxic complications and limitations of conventional and oral therapies. Products at preclinical and clinical stages include formulations of naltrexone and buprenorphine for alcoholism/drug abuse, GLP-1 peptides for diabetes, r-hFSH for fertility, dopamine for nerve growth, dexamethasone for ocular treatment, melanotan for cancer prevention, plasmid DNA for cancer prevention, a variety of vaccines, octreotide generics, etc. Most depot formulations are comprised of biodegradable polymer-excipients that control the rate of drug release and resorbs during/after drug release. The major advantage of depot antipsychotics over oral medication was facilitation of compliance in medication taking. One class of biodegradable polymers that has gained wide acceptance and still attractive today is lactide/ glycolide polymers. The greatest advantage of these degradable polymers is that they are broken down into biologically acceptable molecules that are metabolized and removed from the body via normal metabolic pathways. This versatile delivery system offers the advantage of a very high loading and controlled release of various drug for an extended period of time compared with plain delivery system. New formulations of depression can offer advantages over older formulations in terms of convenience, side effect profiles, efficacy, and/or a fast onset of action.

Oral delivery of the drug is the most preferable route of drug delivery due to the ease of administration, patient compliance and flexibility in the formulations. Recent technological advancements have been made in controlled oral drug delivery systems by overcoming physiological difficulties, such as short gastric residence time and highly variable gastric emptying time. Gastroretentive dosage forms have been designed over the past three decades to overcome these difficulties. Several technical approaches are currently utilized in the prolongation of gastric residence time, including highdensity, swelling and expanding, polymeric mucoadhesive, ion-exchange, raft forming, magnetic and floating drug delivery systems (FDDS), as well as other delayed gastric emptying devices. In this review, the current technological developments of FDDS including patented delivery systems and marketed products, and their advantages and future potential for oral controlled drug delivery are discussed.

Quick-release bromocriptine (bromocriptine-QR) (Cycloset) was approved in 2009 for the treatment of type 2 diabetes. The exact anti-diabetic mechanism of action of bromocriptine-QR has not been elucidated, but the drug may help resetting the circadian dopamine signal. Randomized placebo-controlled trials showed that the mean reduction in hemoglobin A1c (HbA1c) levels by bromocriptine-QR was 0.0-0.2% when compared to baseline and 0.4-0.5% when compared with placebo after 24 weeks of therapy. Withdrawal rates due to adverse effects in patients receiving bromocriptine- QR and placebo were 24% and 11%, respectively. The most common adverse effect of bromocriptine-QR was nausea reported by 32% of patients compared with 7% of patients randomized to placebo. The advantages of bromocriptine- QR were minimal risk of hypoglycemia, neutral effect on weight, and reassuring cardiovascular safety over 1 year of use. However, the drug had multiple drawbacks including modest efficacy, high rates of nausea, lack of long-term efficacy and safety data, and considerable cost. Bromocriptine-QR may be used in patients with type 2 diabetes with mild hyperglycemia (HbA1c close to 7.5%) either as adjunctive treatment to metformin and sulfonylurea (SU) or as monotherapy in patients who are intolerant to both agents.

Polymers have become an indispensable part in the design of a conventional as well as novel drug delivery system. Gum Copal (GC), a novel biomaterial obtained from Agathis species, is evaluated in the present study for its potential application as a matrix former in transdermal drug delivery systems. GC was initially characterized for various physicochemical properties and then mechanical characterization of the Plasticized films of GC was investigated. Verapamil hydrochloride (VH), owing to its pharmacokinetic properties, was selected as the model drug for the present work. Matrix type transdermal films of VH with GC, alone and in combination with polyvinyl pyrrolidone (PVP K-30), were developed and evaluated for various physicochemical properties. In-vitro drug release study was carried out using paddle over disk method and in-vitro skin permeation study was performed using human cadaver skin. On the basis of physicochemical properties, in-vitro drug release study and permeation performance, formulation F5 containing GC: PVP K-30 (60:40) was selected as an optimized formulation for in vivo study. Animal studies were carried out using Dawley rats and the data obtained from the plasma drug analysis showed that peak drug concentration of about 244.94 ± 1.25 ng/mL was achieved in 6 h after the application of the patch and plasma drug concentration was maintained till 24 h. Skin irritancy test results proved the suitability of the biomaterial for transdermal application. The drug polymer interaction studies carried out using UV, FTIR and TLC analysis indicated that drug and polymer were compatible. Due to reasonably good mechanical properties, low water vapor transmission and sustained release capability, GC seems to be a promising film former for transdermal drug delivery.

The ability of peptide nucleic acids (PNA) to enter and to cross filter-grown MDCK, HEK and CHO cells was studied by means of a protocol based on capillary electrophoresis combined with laser-induced fluorescence detection. The used approach avoided possible errors encountered in protocols based on confocal laserscanning microscopy and FACS analysis. In contradiction to the commonly anticipated unability of PNA to cross biomembranes, extensive translocation of unmodified PNA into and across the investigated cell types was found. The transport mode comprised a variety of energy dependent and -independent as well as temperature sensitive mechanisms being probably destined to natural substrates and hijacked by PNA. The presented results suggest active as well as passive export mechanisms rather than poor penetration into cells to be responsible for the only weak biological activity of unmodified PNA.

Percutaneous coronary intervention (PCI) has become a highly effective alternative for the treatment of coronary artery disease. The use of stents has reduced the rates of restenosis by preventing elastic recoil and negative remodeling, however neointima formation still remains an issue. Local drug delivery is an attractive option to maintain effective drug concentrations at the site of arterial injury without risking systemic toxicity. Drug-eluting stents (DESs) are implanted to provide local drug delivery to combat neointima formation by slowing cell proliferation and migration. However, problems still remain with DES use including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, necessity for longer term anti-platelet drug use, and local hypersensitivity to polymer delivery matrices. This review describes recent advances in local drug delivery for the prevention of restenosis. Many different drug therapeutics have been considered, as well as the material properties of the drug delivery systems. Systems for delivery include DESs, balloon catheters, polymeric cuffs and nanoparticles. Our own experience designing a controlled release device for a new therapeutic agent, Serp-1, an anti-inflammatory protein, is briefly presented. The release of Serp-1 can be extended using diffusion controlled release from physically crosslinked poly(vinyl alcohol) hydrogels, where its release properties can be tuned by the processing parameters of the hydrogel.

The purpose of this work is to characterize microchannels created by polymeric microneedles, applied by hand, and to demonstrate enhanced delivery of topically applied formulations of lidocaine hydrochloride and methylprednisolone sodium succinate (MPSS). 3M's Microstructured Transdermal System (MTS) arrays were applied to domestic swine to demonstrate reliability of penetration, depth of penetration and durability of the structures to repeat application and high force. Tissue levels of lidocaine and MPSS following topical application with and without microneedle pretreatment were determined by HPLC-MS analysis following digestion of biopsies. Almost all microneedles penetrate the stratum corneum upon hand force application. The depth of penetration varies from <100μm to nearly 150μm depending on the application force and the firmness of the underlying tissue. The arrays show excellent durability to repeated in-vivo application, with less than 5% of the structures evidencing even minimal tip bending after 16 applications. Under extreme force against a rigid surface, the microneedles bend but do not break. A lidocaine hydrochloride formulation applied topically in-vivo showed ∼340% increase in local tissue levels when the MTS arrays were used to twice pre-treat the skin prior to applying the drug. Local delivery of a topically applied formulation of MPSS was over one order of magnitude higher when the application site was twice pre-treated with the MTS array. 3M's MTS array (marketed as 3M™ Microchannel Skin System) provides repeatable and robust penetration of the stratum corneum and epidermis and enhances delivery of some formulations such as lidocaine hydrochloride.

The present work is aimed to develop new oral drug delivery systems of 5-fluorouracil for the treatment of colorectal cancer by using hydrophilic swellable polymer hydroxy propyl methyl cellulose (HPMC) and pH responsive soluble polymer Eudragit L100 (ED) as coating materials. Core tablets containing 50mg of 5-fluorouracil were prepared by direct compression. The core tablets compression coated with different ratios (9:1, 8:2, 7:3, 6:4 and 5:5) of HPMC and ED with a coat weight of 300 and 400mg. All the formulations were evaluated for the hardness, friability, drug content uniformity and in vitro drug release studies in media of different pH 1.2, 7.4 and 6.8. The formulations released 0 to 7% of the drug in physiological environment of stomach and small intestine depending upon proportion of HPMC and ED used in the coat. Among the different ratios used for coating with HPMC:ED combination, ratio 9:1 gave the best release profile with the coat weight of 300mg (1.34% in the initial 5h and 87% in 24 h). Further increase in the coat weight to 400mg with different ratios of 9:1, 8:2, 7:3, 6:4 and 5:5 led to drug release of 0%, 0%, 0%, 3.47% and 6.25%, respectively in the initial 5 h and 73.52%, 87.03%, 92.18%, 96.33% and 97.61%, respectively, in 24 h. Thus, based on the results of in vitro drug release studies, the ratio 7:3 with a coat weight of 400mg was found to be suitable for targeting 5-fluorouracil to the colon without being released in physiological environment of stomach and small intestine. The formulation showed no change in physical appearance, drug content or in vitro release pattern after storage at 40° C / 75% RH for 3 months. The release of 5-fluorouracil from developed formulation was directly proportional to amount of ED used in the coat. The DSC and FTIR studies indicated no possibility of interaction between 5-fluorouracil and excipients.

The aim of this study was to develop a novel colon targeted matrix tablet containing Metronidazole (MTZ) as model drug. Matrix tablets were prepared using Assam Bora rice starch, which is essentially a natural polymer, by wet granulation technique. The granules prepared were subjected to evaluation for angle of repose, bulk density, compressibility index, Hausner's ratio, total porosity, and drug content. The developed tablets were also analysed for thickness, diameter, weight variation tests, tablet crushing strength, friability, and in vitro release studies. The granules displayed satisfactory flow properties, compressibility, Hausnerapos;s ratio and drug content. Almost all the tablet formulations showed acceptable pharmacotechnical properties and complied with the in-house developed specifications for the tested parameters. Drug release study confirmed to the initial fast release in the acidic environment of surface adhered drug followed by slow release in alkaline media subsequently leading to fast and major drug release in the caecal content. Furthermore, the release of drug was unaffected by the hostile environment of GIT which can be ascribed to microbial degradation, promptly followed by enzymatic degradation. Curve fitting proved that the drug release from the tablets followed the Higuchi model. In vitro bacterial inhibition studies illustrated that the released drugs were able to diffuse through agar medium, inhibiting MTZ sensitive Bacteroides fragilis. The selected MTZ matrix tablets (F1-F6) had zones of inhibition paralleling those of the marketed formulation.

A novel approach in target specific molecular prototype drug delivery system concerns the attempt to employ radical affording substances (RAS) or radical quenching substances (RQS) as prodrugs able to produce irreversible damage on the desired target and therefore to stimulate cellular apoptosis. However, radical species generated can react quickly within the chemical environment prior to reaching its proper site of action. In this short communication, we report our investigations towards developing two alternative novel, simple, flexible and effective drug delivery systems that provide optimal dosage of drugs precisely where and when needed and therefore achieve and sustain a complex delivery profile. We have demonstrated the application of two effective molecular prototype delivery systems able to harness free radical reactivity within the laboratory where biological processes can be studied and controlled, leading to the prevention of disease and the development of new treatments for disease states mediated by free radicals.

The present review provides an insight into various potential areas of dentistry that are being invaded by nanotechnology based drugs and drug delivery systems. Current treatments for diseases of dental and oral structures rely on the use of classical pharmacological agents which, in some cases are limited by low efficacy and lack of selectivity to target cells. However, various nanostructures in drug delivery and their challenges in the field of dentistry have not been reviewed so far in the literature. The different treatment opportunities of importance include caries control restorations, tooth remineralisation, management of dentinal hypersensitivity, dental caries vaccine, management of oral biofilm, root canal disinfection, local anaesthesia and periodontal infection. The authors have also identified few dental applications demanding extensive research to emerge as a promising therapeutic strategy. We conclude by claiming that dentistry should follow the trend of probing matter at nanoscale to achieve a predictable treatment outcome.