Characterisation and in vitro stability of low-dose, lidocaine-loaded poly(vinyl alcohol)-tetrahydroxyborate hydrogels.

Poly(vinyl alcohol) hydrogels cross-linked with the tetrahydroxyborate anion possess textural and rheological properties that can be used as novel drug-loaded vehicles for application to traumatic wounds. However, addition of soluble drug substances causes concentration-dependent phase separation and rheological changes. The aim of this work was to investigate the effect of adding a local anaesthetic, but keeping the concentration low in an attempt to prevent these changes. Cross-linked hydrogels prepared from three grades of poly(vinyl alcohol) were characterised rheologically. Temperature sweep studies showed an elevated complex viscosity upon moving from 25°C to 80°C, which remained high for 48 h following completion of the cycle. Adhesion to model dermal surfaces achieved a maximum of 2.62 N cm(-2) and were greater than that observed to epidermal substrates, with a strong dependence on the rate of detachment used during testing. An optimised formulation (6% w/w PVA (31-50; 99) and 2% w/w THB) containing lidocaine hydrochloride loaded to an upper maximum concentration of 1.5% w/w was assessed for phase separation and drug crystallisation. After six months, crystallisation was present in formulations containing 0.7% and 1.5% lidocaine HCl. Changes in pH in response to increases in lidocaine loading were low. Drug release was shown to operate via a non-Fickian process for all three concentrations, with 60% occurring after approximately 24h. It can be concluded that using a low concentration of lidocaine hydrochloride in hydrogels based on poly(vinyl alcohol) will result in crystallisation. Furthermore, these hydrogels are unlikely to induce rapid anaesthesia due to the low loading and slow release kinetics.

State of the art in benefit-risk analysis: medicines.

Benefit-risk assessment in medicine has been a valuable tool in the regulation of medicines since the 1960s. Benefit-risk assessment takes place in multiple stages during a medicine's life-cycle and can be conducted in a variety of ways, using methods ranging from qualitative to quantitative. Each benefit-risk assessment method is subject to its own specific strengths and limitations. Despite its widespread and long-time use, benefit-risk assessment in medicine is subject to debate and suffers from a number of limitations and is currently still under development. This state of the art review paper will discuss the various aspects and approaches to benefit-risk assessment in medicine in a chronological pathway. The review will discuss all types of benefit-risk assessment a medicinal product will undergo during its lifecycle, from Phase I clinical trials to post-marketing surveillance and health technology assessment for inclusion in public formularies. The benefit-risk profile of a drug is dynamic and differs for different indications and patient groups. In the end of this review we conclude benefit-risk analysis in medicine is a developed practice that is subject to continuous improvement and modernisation. Improvement not only in methodology, but also in cooperation between organizations can improve benefit-risk assessment.

Clinical and immunohistochemical assessment of vulval intraepithelial neoplasia following photodynamic therapy using a novel bioadhesive patch-type system loaded with 5-aminolevulinic acid.

BACKGROUND: The work in this study appraised photodynamic treatment (PDT) as a treatment method for vulval intraepithelial neoplasia (VIN) using a novel bioadhesive patch to deliver aminolevulinic acid. An analysis of changes in expression of apoptotic and cell cycle proteins (p53, p21, Mdm2, Blc-2, Bax, Ki-67) in response to PDT was evaluated. METHODS: PDT was performed using non-laser light, either as a one or two-cycle treatment, with clinical and pathological assessment following after 6 weeks. Twenty-three patients with 25 VIN lesions underwent 49 cycles of PDT. Patches were designed to conform to uneven vulval skin and contained 38 mg cm(-2) aminolevulinic acid. Assessment was carried out at 6 weeks post-treatment. Patient-based treatment assessment, along with clinical and pathological changes, were monitored. Immunohistochemical staining was used to elucidate a possible biomolecular basis for induced cellular changes. RESULTS: Most patients (52%) reported a symptomatic response, with normal pathology restored in 38% of lesions. The patch was easy to apply and remove, causing minimal discomfort. Fluorescence inspection confirmed protoporphyrin accumulation. Pain during implementation of PDT was problematic, necessitating some form of local analgesia. Changes in expression of cell cycle and apoptotic-related proteins suggested involvement of apoptotic pathways. Down regulation of p21 and inverse changes in Bcl-2 and Bax were key findings. CONCLUSION: Treatment of VIN lesions using a novel bioadhesive patch induced changes in cell cycle and apoptotic proteins in response to PDT with possible utilisation of apoptotic pathways. The efficacy of PDT in treating VIN could be improved by a better understanding of these apoptotic mechanisms, the influence of factors, such as HPV status, and of the need for effective pain management.

Comparison of the cidal activity of tea tree oil and terpinen-4-ol against clinical bacterial skin isolates and human fibroblast cells.

AIMS: The aim of this study was to compare both the antimicrobial activity of terpinen-4-ol and tea tree oil (TTO) against clinical skin isolates of meticillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS) and their toxicity against human fibroblast cells. METHODS AND RESULTS: Antimicrobial activity was compared by using broth microdilution and quantitative in vitro time-kill test methods. Terpinen-4-ol exhibited significantly greater bacteriostatic and bactericidal activity, as measured by minimum inhibitory and bactericidal concentrations, respectively, than TTO against both MRSA and CoNS isolates. Although not statistically significant, time-kill studies also clearly showed that terpinen-4-ol exhibited greater antimicrobial activity than TTO. Comparison of the toxicity of terpinen-4-ol and TTO against human fibroblasts revealed that neither agent, at the concentrations tested, were toxic over the 24-h test period. CONCLUSIONS: Terpinen-4-ol is a more potent antibacterial agent against MRSA and CoNS isolates than TTO with neither agent exhibiting toxicity to fibroblast cells at the concentrations tested. SIGNIFICANCE AND IMPACT OF THE STUDY: Terpinen-4-ol should be considered for inclusion as a single agent in products formulated for topical treatment of MRSA infection. However, further work would initially be required to ensure that resistance would not develop with the use of terpinen-4-ol as a single agent.

Incorporation of novel 1-alkylcarbonyloxymethyl prodrugs of 5-fluorouracil into poly(lactide-co-glycolide) nanoparticles.

Incorporation of 1-alkylcarbonyloxymethyl prodrugs of 5FU into poly(lactide-co-glycolide) nanoparticles using nanoprecipitation methods gave increased loading efficiencies over that obtained using the parent drug substance. SEM studies revealed spherical nanoparticles of around 200nm in diameter, corresponding well with measurements made using photon correlation spectroscopy. The C(7) prodrug gave the best mean loading of 47.23%, which compared favourably to 3.68% loading achieved with 5FU. Loading efficiency was seen to follow the hydrophilic-lipophilic balance in the homologue series, where increases in lipophilicities alone were not good predictors of loading. Drug release, in terms of resultant 5FU concentration, was monitored using a flow-through dissolution apparatus. Cumulative drug release from nanoparticles loaded with the C(5) prodrug was linear over 6h, with approximately 14% of the total available 5FU dose released and with no evidence of a burst effect. The flux profile of the C(5)-loaded nanoparticles showed an initial peak in flux in the first sampling interval, but became linear for the remainder of the release phase. C(7)-loaded nanoparticles released considerably less (4% in 6h) with a similar flux pattern to that seen with the C(5) prodrug. The C(9)-loaded nanoparticles released less than 1% of the available 5FU over 6h, with a similar zero-order profile. The C(7) prodrug was deemed to be the prodrug of choice, achieving the highest loadings and releasing 5FU, following hydrolysis, in a zero-order fashion over a period of at least 6h. Given the lack of burst effect and steady-state flux conditions, this nanoparticulate formulation offers a better dosing strategy for sustained intravenous use when compared to that arising from nanoparticles made by direct incorporation of 5FU.

Sustained release of 5-fluorouracil from polymeric nanoparticles.

The use of biodegradable nanoparticles loaded with 5-fluorouracil was investigated as a potential means to sustain the release of this drug. Nanoparticles prepared from four biodegradable polymers were loaded with 5-fluorouracil using three loading concentrations of drug and three different concentrations of added polymer. Washing particles using a centrifugation/re-suspension with ultrasound protocol was found to dislodge the majority of drug, resulting in an over-estimation of incorporation efficiency and low levels of strongly entrapped drug. Increasing the initial 5-fluorouracil concentration before polymer/monomer addition increased the drug loading in both washed and unwashed particles. Increasing the amount of polymer used to make nanoparticles did not increase loadings, but did produce increased amounts of unusable polymer waste. Drug release from nanoparticles was evaluated using a Franz cell diffusion apparatus, which showed an initial burst effect followed by a slower release phase over 24 h. Indeed, nanoparticles prepared from poly(lactide-co-glycolide) released 66% of their 5-fluorouracil payload over this period. It was concluded that 5-fluorouracil-loaded nanoparticles could be readily included into a hydrogel-based delivery system to provide sustained drug release for trans-epithelial drug-delivery applications.

Response surface methodology as a predictive tool for determining the effects of preparation conditions on the physicochemical properties of poly(isobutylcyanoacrylate) nanoparticles.

Preparation conditions of nanoparticles greatly influence their physicochemical characteristics. A factorial design was used to evaluate the influence of these conditions on the particle diameter, zeta potential, polydispersity, percentage recovery, and molecular weight of poly(isobutylcyanoacrylate) nanoparticles. The relationship between these responses and the effects of simultaneously varying three preparation factors (monomer concentration, surfactant concentration, pH of the polymerization medium) were modelled by response-surface methodology. Three levels were chosen for each factor, giving 27 trials. The responses obtained in the experimental design were found to be modelled by either a reduced quadratic or second-order model. Particle diameter was found to be a function of the pH, whereas zeta potential depended on pH and to a lesser extent of the monomer concentration. Polydispersity depended on the pH and an interaction term between pH and the surfactant concentration. The particle recovery was significantly influenced by all three factors, whereas the pH was the primary influence on the molecular weight. Thus, response surface methodology gave detailed information on the predicted physicochemical characteristics found on poly(isobutylcyanoacrylate) nanoparticles prepared using a wide range of experimental conditions.

A randomised controlled trial evaluating a novel cytotoxic drug delivery system for the treatment of cervical intraepithelial neoplasia.

OBJECTIVE: To investigate the efficacy of a novel method for the treatment of cervical intraepithelial neoplasia. A cytotoxic drug delivery system using a bilaminar bioadhesive polymeric film was applied directly to the cervix. This cytotoxic drug delivery system allowed the dose, the site and the duration of application of the cytotoxic drug (5-fluorouracil) to be controlled. DESIGN: A prospective, double-blind randomised controlled trial. SETTING: The Departments of Obstetrics and Gynaecology and Pathology of Belfast City Hospital and The Queen's University of Belfast, and the Department of Pharmacy of The Queen's University of Belfast. PARTICIPANTS: One hundred and four patients who had been referred to the colposcopy outpatient clinic because of abnormal cervical cytology were recruited into the trial. They were assessed colposcopically and biopsies for histopathology were obtained. Only patients with cervical intraepithelial neoplasia lesions Grades 1 and 2 were recruited. INTERVENTIONS: All patients were re-assessed one, three, and six months after application of the cytotoxic drug delivery system by colposcopy. Clinical endpoints were noted. MAIN OUTCOME MEASURES: Pre-treatment histopathological biopsy results were compared with those obtained after treatment. RESULTS: The cytotoxic drug delivery system fulfilled the requirements for treatment of cervical intraepithelial neoplasia without causing any architechtural damage, but the chemotherapeutic agent, 5-fluorouracil, did not provide effective treatment of disease. CONCLUSIONS: This study showed that the delivery system was effective, and further studies using this mechanism are now possible.

Autoradiographic imaging of the distribution of 5-fluorouracil through cervical tissue following in vitro surface application of a bioadhesive cervical patch.

The distribution of 5-fluorouracil through cervical tissue has been assessed following the in vitro application of a bioadhesive patch to excised human cervix. The bioadhesive matrix contained a total of 20 mg of 5-fluorouracil spiked with 5-fluorouracil-6-3H and was applied for fixed periods of either 4 or 24 hours. Tissue slices were sectioned perpendicular to the plane of the applied patch and the autoradiographic image developed by placing a frozen tissue slice on Hyperfilm with subsequent instant thawing and refreezing, the resulting bilayer being maintained at -18 degrees C for 24 hours. The developed image was analysed by scanning densitometry and raster scans were visualised with three-dimensional contouring software. The autoradiograms showed darker areas surrounding tissue ducts, suggesting that 5-FU was spilling from the lumen into the surrounding stroma. Transport of 5FU via aqueous channels may thus make an important contribution to the rapid penetration of the drug through the cervical stroma. Three-dimensional autoradiographic images showed that, for a 4-hour patch application, there were areas of relatively low drug concentration within the upper 5 mm of tissue, where CIN lesions can exist in the glandular tissue or cervical crypts. However, extending the application time to 24 hours produced areas of high drug concentration extending throughout this region.

Liquid scintillation spectrometry of 5-fluorouracil in cervical tissue following in vitro surface application of a bioadhesive cervical patch.

The potential use of bioadhesive technology for the treatment of cervical intraepithelial neoplasia was investigated. A cervical patch was designed containing 5-fluorouracil in a bioadhesive matrix and polyvinyl chloride as the backing layer. The concentration of 5-fluorouracil at specified tissue depths from the cervical surface was determined in vitro in relation to the ability of the drug to reach precancerous foci in cervical crypts up to 4 mm below the tissue surface. Thus, tissue was exposed to drug-loaded patches spiked with 5-fluorouracil-6-3H and subsequently sectioned to obtain tissue slices at different depths. The concentration of 5-fluorouracil was determined by liquid scintillation spectrometry. Drug penetration into cervical tissue exceeded a depth of 5.5 mm. Furthermore, the concentration in the tissue depended on the drug loading in the patch. Patches containing 10 and 20 mg of 5-fluorouracil produced a linear drug gradient that was established after a 4 hour application of the patch and persisted over 24 hours. However, patches containing 3.5 mg of 5-fluorouracil displayed signs of drug exhaustion after 24 hours. The penetration characteristics of 5-fluorouracil through cervical tissue using the cervical patch delivery system were sufficiently favourable to warrant further clinical investigations.