Lecithin vesicles for topical delivery of diclofenac.

Skin penetration of topically applied diclofenac is important for the treatment of rheumatic diseases and actinic keratoses. We have studied the permeation of diclofenac across human cadaver epidermis in-vitro from four lecithin vesicle formulations and a few marketed semi-solid preparations. The lecithin vesicle formulations were prepared by dissolving the lipid contents (lecithin and sodium cholate) in a 1:1 mixture of methanol-chloroform, evaporating the solvents under vacuum, and hydrating the lipid layer with the drug solution in water or 10% ethanol. The vesicles were sonicated for 5 min to reduce the vesicle size and their size and Zeta potential were characterized. The cumulative amount and maximum flux of diclofenac was 69.7+/-40.3 micrograms and 4.77+/-3.16 micrograms/hcm(2) from lecithin vesicles containing sodium cholate and 10% ethanol, and is the highest of all formulations studied. The cumulative amount and mean maximum flux obtained from other formulations were in the range of 2.46+/-1.98-29.9+/-10.1 micrograms and 0.53+/-0.46-3.61+/-0.86 micrograms/hcm(2). Based on the results, lecithin vesicles of diclofenac appear to be advantageous for the topical delivery of diclofenac.     

The effect of varying impact energy on diffuse axonal injury in the rat brain: a preliminary study

Diffuse axonal injury (DAI) is seen as widespread damage in the white matter of brain characterized by morphological changes to axons throughout the brain and brain stem. The current study attempted to investigate the effect of increasing impact energy on the presence and severity of DAI in corpus callosum (CC). DAI was induced in adult male Sprague-Dawley rats using an injury model adapted from Marmarou et al. in 1994. A 450-g cylindrical brass weight was dropped from three different heights (2.0 m, 1.5 m and 1.0 m) on to a metal helmet affixed to the skull of the rats. In the sham group, rats underwent a surgical procedure with no impact. After a 24-h survival period the animals were transcardially perfused. The brain was removed and the cerebral hemispheres were sectioned with a vibrotome and stained by silver impregnation technique. The CC of all the impacted rats showed DAI in the form of beaded axons, retraction balls and vacuole-like enlargements. The axonal injury was most severe in the 2-m group, while mildest in the 1-m group. In the sham group, axons appeared to be normal. This study demonstrates evidence of graded DAI depending on the impact energy. Such data is useful for mathematical modeling of axonal injury in rat brain using the same impact parameters and potential determination of injury thresholds for neural trauma. Electronic Publication     

Pharmacokinetics of pentoxifylline after oral administration of a sustained release tablet at two different times of the day.

The pharmacokinetics of pentoxifylline (CAS-6493-05-6) was studied in healthy subjects by orally administering a 400 mg sustained release tablet (Trental) at two different times (10:00 or 22:00 h) of the day in a crossover design. Pentoxifylline concentrations in serum samples were estimated by using high performance liquid chromatography. The mean values of Cmax (326.38 +/- 39.77 vs 266.35 +/- 36.0 ng/ml, p < 0.01, n = 8), AUC0-t (2424 +/- 382 vs 2141 +/- 300 ng/ml/h, p < 0.05, n = 8) were significantly higher and Vss/f (16537 +/- 2869 vs 20136 +/- 5006 ml/kg), Vd/f (11807 +/- 2704 vs 15801 +/- 5960 ml/kg) were significantly (p < 0.05, n = 8) lower following morning (10:00 h) administration than in the night (22:00 h). These variations should be considered while designing sustained release dosage forms.     

LC determination and purity evaluation of nefazodone HCl in bulk drug and pharmaceutical formulations

A thin layer chromatographic-densitometric method for identification and quantitation of neomycin sulfate, polymixin B sulfate, zinc bacytracin and auxiliary substances (methyl and propyl hydroxybenzoates) in ophthalmic ointment was developed. To separate these constituents the silica gel coated TLC plates and two mobile phases were used. The suitable mobile phases were: methanol-n-butanol-ammonia 25%-chloroform (14:4:9:12, v/v/v/v) for determination of antibiotics and n-pentane-glacial acetic acid (66:9, v/v) for methyl and propyl hydroxybenzoates. The antibiotic chromatograms were detected by using ninhydrin ethanol solution, while densitometric measurements were made at lambda = 550 nm. Hydroxybenzoates were identified by UV measurements at lambda = 260 nm. The constituents under consideration were well separated at sufficient detection level. The recovery for all constituents ranged from 98.08% to 104.95%.     

Neurophysiological and biomechanical characterization of goat cervical facet joint capsules.

Cervical facet joints have been implicated as a major source of pain after whiplash injury. We sought to identify facet joint capsule receptors in the cervical spine and quantify their responses to capsular deformation. The response of mechanosensitive afferents in C5-C6 facet joint capsules to craniocaudal stretch (0.5 mm/s) was examined in anaesthetized adult goats. Capsular afferents were characterized into Group III and IV based on their conduction velocity. Two-dimensional strains across the capsules during stretch were obtained by a stereoimaging technique and finite element modeling. 17 (53%) Group III and 14 (56%) Group IV afferents were identified with low strain thresholds of 0.107+/-0.033 and 0.100+/-0.046. A subpopulation of low-strain-threshold afferents had discharge rate saturation at the strains of 0.388+/-0.121 (n=9, Group III) and 0.341+/-0.159 (n=9, Group IV). Two (8%) Group IV units responded only to high strains (0.460+/-0.170). 15 (47%) Group III and 9 (36%) Group IV units could not be excited even by noxious capsular stretch. Simple linear regressions were conducted with capsular load and principal strain as independent variables and neural response of low-strain-threshold afferents as the dependent variable. Correlation coefficients (R2) were 0.73+/-0.11 with load, and 0.82+/-0.12 with principal strain. The stiffness of the C5-C6 capsules was 16.8+/-11.4 N/mm. Our results indicate that sensory receptors in cervical facet joint capsules are not only capable of signaling a graded physiological mechanical stimulus, but may also elicit pain sensation under excessive deformation.     

Pain generation in lumbar and cervical facet joints

Facet joints are implicated as a major source of neck and low-back pain. Both cervical and lumbar facet syndromes have been described in the medical literature. Biomechanical studies have shown that lumbar and cervical facet-joint capsules can undergo high strains during spine-loading. Neuroanatomic studies have demonstrated free and encapsulated nerve endings in facet joints as well as nerves containing substance P and calcitonin gene-related peptide. Neurophysiologic studies have shown that facet-joint capsules contain low-threshold mechanoreceptors, mechanically sensitive nociceptors, and silent nociceptors. Inflammation leads to decreased thresholds of nerve endings in facet capsules as well as elevated baseline discharge rates. Recent biomechanical studies suggest that rear-end motor-vehicle impacts give rise to excessive deformation of the capsules of lower cervical facet joints. Still unresolved is whether this stretch is sufficient to activate nociceptors in the joint capsule. To answer this question, recent studies indicate that low stretch levels activate proprioceptors in the facet-joint capsule. Excessive capsule stretch activates nociceptors, leads to prolonged neural afterdischarges, and can cause damage to the capsule and to axons in the capsule. In instances in which a whiplash event is severe enough to injure the joint capsule, facet capsule overstretch is a possible cause of persistent neck pain.     

A validated stability indicating ion-pair RP-LC method for zoledronic acid

The present paper describes the development of a stability indicating high performance liquid chromatographic (HPLC) assay method for zoledronic acid in the presence of its impurities and degradation products generated from forced decomposition studies. The drug substance was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The degradation of zoledronic acid was observed under oxidative stress at higher temperature. The drug was found to be stable in other stress conditions attempted. Successful separation of the drug from the degradation products formed under stress conditions was achieved on a C18 column using a mixture of phosphate buffer that contains 7 mM tetra butyl ammonium hydrogen sulphate, an ion-pairing agent and methanol (95:5) as mobile phase. The developed HPLC method was validated with respect to response function, precision, accuracy, specificity and robustness. The developed HPLC method to determine the related substances and assay determination of zoledronic acid can be used to evaluate the quality of regular production samples. It can be also used to test the stability samples of zoledronic acid.     

Tensile stretching of cervical facet joint capsule and related axonal changes

This study examines axonal changes in goat cervical facet joint capsules (FJC) subjected to low rate loading. Left C5–C6 FJC was subjected to a series of tensile tests from 2 mm to failure using a computer-controlled actuator. The FJC strain on the dorsal aspect was monitored by a stereo-imaging system. Stretched (n = 10) and unstretched (n = 7) capsules were harvested and serial sections were processed by a silver impregnation method. The mean peak actuator displacement was 21.3 mm (range: 12–30 mm). The average peak strain encompassing various regions of the capsule was 72.9 ± 7.1%. Complete failure of the capsule was observed in 70% of the stretched capsules. Silver impregnation of the sections revealed nerve fibers and bundles in all the regions of the capsule. A blinded analysis of digital photomicrographs of axons revealed a statistically significant number of swollen axons with non-uniform caliber in stretched FJCs. Axons with terminal retraction balls, with occasional beaded appearance or with vacuolations were also observed. Stretching the FJC beyond physiological range could result in altered axonal morphology that may be related to secondary or delayed axotomy changes similar to those seen in central nervous system injuries where axons are subjected to stretching and shearing. These may contribute to neuropathic pain and are potentially related to neck pain after whiplash events.     

Development and validation of a stability indicating LC method for the assay and related substances determination of Exemestane, an aromatase inhibitor

A selective stability indicating HPLC method was developed and validated for quantification of impurities (process related and degradants) and assay determination of Exemestane. Stability indicating power of the method was established by forced degradation experiments and mass balance study. The chromatographic separation was achieved with Hypersil BDS-C-18 using gradient elution. The developed method is validated for parameters like accuracy, linearity, LOD, LOQ, ruggedness. Box–Behnken experimental design was applied to check the robustness of the method.     

Spatial alterations in endothelin receptor expression are temporally associated with the altered microcirculation after brain trauma

OBJECTIVES: To study the cellular distribution of endothelin receptors A and B (ETrA and ETrB) in the post-traumatic sensorimotor cortex and hippocampus. MATERIALS AND METHODS: We inflicted closed head trauma to male Sprague-Dawley rats and visualized ETrA and ETrB immunoreactivity with 3,3'-diaminobenzidine. RESULTS: ETrA immunolabeling was the most prominent in pyramidal neurons 24 and 48 hours post-trauma, while it reached its peak in the microvasculature at hour 4. ETrB immunolabeling was observed in endothelial cells, perivascular neurons, smooth muscle cells (SM) and pericytes, the expression being the most pronounced 24 hours post-trauma. DISCUSSION: The results suggest that the vasoconstrictor effect of endothelin-1 (ET-1) is mediated primarily by ETrA. The dual effects of ETrB are reflected in its vasoconstrictor role at the vascular bed and conversely, in the attenuation of ET-1 availability and synthesis. We conclude that both receptors play a role in the disturbed microvascular autoregulation and in the sustained reduction of blood flow following trauma to the brain.