Current Drug Delivery - Volume 4, Issue 3, 2007

One of the possible sites of action of the analgesic effect of morphine is the Nucleus Raphe Magnus, as morphine injected into this structure induces analgesia in transient pain models. In order to test if morphine in the Nucleus Raphe Magnus is also analgesic in a tonic pain model, 5 μg of morphine or saline (control) were microinjected into the Nucleus Raphe Magnus of the rat. Analgesic effects were assessed following nociceptive stimulation using transient heating of the tail (phasic pain) and subcutaneous orofacial injection of 1.5 % formalin (tonic pain). While morphine was strongly analgesic for the tail-flick response (p <0.0001 compared to control), analgesia on the response to formalin was also observed for both early (p = 0.007) and late responses (p = 0.02). However, the response to formalin was not completely blunted. These results suggest that the Nucleus Raphe Magnus is not the exclusive site of action of morphineinduced analgesia in clinical conditions.

The present study was aimed at developing a sustained release formulation of Nimodipine (NIM) nanoparticles using the biodegradable polymers, poly (lactide-co-glycolide) (PLGA 50:50 and 85:15) as carrier. NIM is a widely used calcium channel blocker which has to be administered as an intravenous infusion for a prolonged period of 1-2 weeks in the treatment of cerebral vasospasm. A sustained release biodegradable formulation would serve to replace this conventional therapy of continuous intravenous administration. PLGA nanoparticles were prepared by a modified precipitation method using high pressure homogenizer at 10, 000 to 14,000 psi. A 32 factorial design was applied for optimization of the formulation parameters and for studying the effect of two independent variables [drug: polymer ratio and concentration of surfactant (Pluronic F 127)] on entrapment efficiency and mean particle size (response variables). Contour plots were plotted which gave a visual representation of the two variables on the dependent variables and also indicated nonlinear relationship between them. The nanoparticles had particle size of 131±1.9 nm for PLGA 50:50 and196±2.2 nm for PLGA 85:15. Scanning Electron Microscopy studies indicated that nanoparticles had spherical shape with a regular surface. The nanoparticles had high entrapment efficiency (96.42±2.09 % for PLGA 50:50 and 94.50±1.25 % for PLGA 85:15). DSC thermograms indicated that NIM was dispersed as an amorphous state in the nanoparticles. In vitro drug release from the lyophilized nanoparticles showed 94.35 ± 3.8 % NIM release from PLGA (50:50) nanoparticles and 63.32 ± 4.6 % release from PLGA (85:15) nanoparticles in 25 days. The release was first ordered and fickian diffusion kinetics in both the cases. These preliminary results indicate that NIM loaded PLGA nanoparticles could be effective in sustaining its release for a prolonged period. However, further studies are needed to confirm its performance in vivo.

Chronic wounds display aberrant wound healing or wound healing that deviates from normal. The term ‘chronic wounds’, implies that these wounds do not heal in a timely fashion. They are often predisposed to infection, and not uncommonly result in amputation. Growth factors and cytokines play a pivotal role in cutaneous wound healing. It has been noted that some growth factors are deficient in chronic wounds, therefore it has been suggested that local or topical application of these factors may compensate for any deficiency and allow normal wound healing to progress. This paper reviews current work on the application of topical growth factors to wounds. Some potential problems are identified and suggestions are made for future areas where research may improve the effectiveness of this form of therapy.

Six new 1-alkylazacycloalkan-2-one esters of ketorolac (1-6) were synthesized and evaluated as potential dermal prodrugs. In vitro experiments were carried out to evaluate their chemical and enzymatic stability and permeation through excised human skin. Furthermore, partition coefficients n-octanol-water of ketorolac and its esters were determined to obtain information about their lipophilicity. Esters 1-6 showed increased lipophilicity compared to the parent drug, good stability in phosphate buffer pH 7.4, and were readily hydrolyzed in human plasma. Results from in vitro percutaneous absorption studies showed that, among all esters synthesized, only for esters 2 and 4 did a higher cumulative amount of drug penetrate through the skin, compared with that obtained after topical application of ketorolac.

Mitochondrion, the energy generating organelle of the cell, is a subject of interest for selective targeting of therapeutic molecules, both Drugs and DNA, since it is found to be involved in numerous disorders like diabetes, neurodegenerative disease and cancer etc. Mitochondrial therapy can be made possible if the bioactive molecule is selectively delivered to the mitochondria of correct cell type, using cell specific ligands and mitochondriotropic molecules in designing of cell selective mitochondria specific carrier system. In this present review we will elaborate the role of mitochondria in human disease, cell specific ligands, mitochondriotropic molecules and their utilization in construction of such cell selective and mitochondria specific delivery systems that will make mitochondrial medicine practically possible.

In this review we explore and integrate the knowledge of the plausible pharmacological targets that could explain the new application for the well known semi-synthetic, tetracycline-derivate minocycline as a cytoprotective drug. In doing so, we will analyze the possible mechanisms to elucidate the potential cytoprotective properties of minocycline. We address its anti-oxidant action ranging from its structure to its capacity to modulate the expression of oxidant-related enzymes such as nitric oxide synthase. The pharmacological targets responsible for its anti-inflammatory effects are surveyed. The effects of this antibiotic are making its marks on intracellular pathways related to neurodegenerative processes such as mitochondrially-mediated apoptosis, including minocycline-modulated effects on the expression of apoptotic proteins. Finally, we will explore the effects of minocycline on metalloproteinases, enzymes implicated in the modulation of cerebrovascular post-ischemic oxidative reperfusion injury, and new targets. In conclusion, we shed new light on the shadowy controversy of minocycline's potential cytoprotective mechanisms and targets of action.

Bioresorbable polymers offer the potential to deliver biologically active agents that selectively modulate wound healing in bone and periodontal regeneration. This preliminary study characterizes early wound healing in calvarial defects grafted with demineralized bone matrix (DBM) overlaid with membranes made from a novel class of non-steroidal anti-inflammatory drug (NSAID)-derived poly(anhydride-esters). These polymers chemically incorporate either salicylic acid (SA) or 5-(2',4'-difluorophenyl)salicylic acid (diflunisal) into the polymeric backbone and release the NSAIDs upon hydrolysis. Inflammatory cell infiltrate in response to the novel NSAID-derived polymers was compared to defects grafted with DBM alone at 10 days and to defects grafted with DBM and overlaid with poly(lactic acid) (PLA; Atrisorb®) at 21 days in 8 Wistar rats (350-450 g). Histological analysis of the calvarial sites at 10 days revealed that the NSAIDderived polymers were associated with moderate levels of inflammation similar to defects grafted without polymer (2.3 ± 0.96 versus 2.0 ± 0.82, respectively), consistent with the therapeutic activity of salicylic acid and diflunisal. Defects grafted with DBM and overlaid with NSAID-derived polymers at 21 days exhibited mild inflammation; whereas, defects treated with PLA were consistently associated with moderate to severe inflammatory cell infiltrate (1.8 ± 0.50 versus 2.7 ± 0.58, respectively). Histopathological findings, such as foreign body giant cells or fibrous encapsulation, were not observed in any defects with NSAID-derived polymers. Cellular features consistent with bone formation were found in all grafted defects. This novel class of non-steroidal anti-inflammatory drug-derived poly(anhydride-esters) were well tolerated and elicited no demonstrable increase in inflammation, as shown with PLA, during osseous wound healing in a regenerative application.

The purpose of this preliminary study was to investigate the physico-chemical properties of nimesulide precipitated by continuous supercritical antisolvent (SAS) from different organic solvents like acetone, chloroform and dichloromethane at 40°C and 80, 85 and 88 bar, respectively. Scanning electron microscopy, differential scanning calorimetry, X-Ray diffractometry and in vitro dissolution tests were employed to study how the technological process and the solvent nature would affect the final product. SAS-processed nimesulide particles showed dramatic morphological change in crystalline structure if compared to native nimesulide, resulting in needle and thin rods shaped crystals. The solid state analysis showed that using chloroform or dichloromethane as a solvent the drug solid state remained substantially unchanged, whilst if using acetone the applied method caused a transition from the starting form I to the meta-stable form II. So as to identify which process was responsible for this result, nimesulide was further precipitated from the same solvent by conventional evaporation method (RV-sample). On the basis of this comparison, the solvent was found to be responsible for the re-organization into the different polymorphic form and the potential of the SAS process to produce micronic needle shaped particles, with an enhanced dissolution rate if compared to the to the pure drug, was ascertained. Finally, the stability of the nimesulide form II, checked by DSC analysis, was ruled on over a period of 15 months.

Metformin microspheres with sodium alginate alone and in combination with gellan were prepared using an emulsion-cross linking method. The prepared microspheres were evaluated for their physico-chemical characteristics like particle size, morphology using SEM, incorporation efficiency, equilibrium water content (swelling) and in vitro drug release. The effect of various formulation variables like polymer concentration (sodium alginate; and proportion of gellan in microspheres prepared by a combination of sodium alginate and gellan), drug loading, crosslinking agent concentration and cross-linking time on the in vitro dissolution of the prepared microspheres were evaluated. The results showed that both the particle size and the incorporation efficiency were proportional to the polymer concentration. In case of microspheres containing both sodium alginate and gellan, the mean diameter and the incorporation efficiency were higher than the corresponding microspheres containing only alginate, both increasing with an increase in proportion of gellan. The prepared microspheres were found to be discrete and spherical in shape and were successful in sustaining the drug release for 8 hours. Incorporation of gellan caused a significant decrease in drug release. The release followed a biphasic profile, in all cases, characterized by an initial phase of moderate drug release followed by a phase of higher release. Further, the kinetic treatment of the dissolution data revealed the prevalence of matrix diffusion kinetics.