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Biomedical subjects

P Davidson

Publications and source records attributed to P Davidson.

At least 19 recordsLinked to original sources
PubMed2006

Sex worker health: San Francisco style.

OBJECTIVES: To describe the characteristics of sex workers accessing care at a peer based clinic in San Francisco and to evaluate predictors of sexually transmitted infections (STI). METHODS: We conducted an observational study of sex workers at St James Infirmary. Individuals underwent an initial questionnaire, and we offered screening for STI at each clinic visit. We performed univariate, bivariate, and multivariable analyses to assess for predictors of STI in this population. RESULTS: We saw 783 sex workers identifying as female (53.6%), male (23.9%), male to female transgender (16.1%), and other (6.5%). 70% had never disclosed their sex work to a medical provider. Participants represented a wide range of ethnicities, educational backgrounds, and types of sex work. The most common substance used was tobacco (45.8%). Nearly 40% reported current illicit drug use. Over half reported domestic violence, and 36.0% reported sex work related violence. Those screened had gonorrhoea (12.4%), chlamydia (6.8%), syphilis (1.8%), or herpes simplex virus 2 (34.3%). Predictors of STI included African-American race (odds ratio (OR) 3.3), male gender (OR 1.9), and sex work related violence (OR 1.9). In contrast, participants who had only ever engaged in collective sex work were less likely to have an STI (OR 0.4). CONCLUSIONS: The majority of sex workers have never discussed their work with a medical provider. Domestic violence is extremely prevalent as is work related violence. Working with other sex workers appears to be protective of STIs. STI prevention interventions should target African-American and male sex workers. Addressing violence in the workplace and encouraging sex workers to work collectively may be effective prevention strategies.

Adolescent↗
PubMed2006

Magnetic-field-induced orientational order in the isotropic phase of hard colloidal platelets.

The magnetic-field-induced orientational order in the isotropic phase of colloidal gibbsite [Al(OH)3] platelets is studied by means of optical birefringence and small-angle x-ray scattering (SAXS) techniques. The suspensions display field-induced ordering at moderate field strengths (a few Tesla), which increases with increasing particle concentration. The gibbsite particles align their normals perpendicular to the magnetic field and hence possess a negative anisotropy of their diamagnetic susceptibility Delta(chi). The results can be described following a simple, Onsager-like approach. A simplified model is derived that allows one to obtain the orientational distribution function directly from the scattering data. However, it leads to an underestimate of the diamagnetic susceptibility anisotropy Delta(chi). This accounts for the difference between the Delta(chi) values provided by the two experimental techniques (SAXS and magneto-optics). The order of magnitude Delta(chi) approximately 10(-22) J/T(2) lies in between that of goethite suspensions and that of suspensions of organic particles.

Journal Article↗
PubMed2006

Adefovir dipivoxil and pegylated interferon alfa-2a for the treatment of chronic hepatitis B: a systematic review and economic evaluation.

OBJECTIVES: To assess the clinical effectiveness and cost-effectiveness of adefovirdipivoxil (ADV) and pegylated interferon alfa-2a (PEG) for the treatment of adults with chronic hepatitis B infection (CHB). DATA SOURCES: Electronic databases for the period from 1995-6 to April 2005. Websites of the relevant organisations. REVIEW METHODS: Searches were made for studies of clinical effectiveness, cost-effectiveness, quality of life, resource use/costs and epidemiology/natural history. Randomised controlled trials (RCTs) were included that compared PEG and ADV with currently licensed treatments for CHB, including non-pegylated ('standard') interferon alfa (IFN), lamivudine (LAM), and best supportive care. The trials were reviewed in a narrative synthesis but meta-analysis was not undertaken owing to heterogeneity in the interventions and comparators evaluated. A model was developed to estimate the cost-effectiveness (cost-utility) of PEG and of ADV compared with IFN, LAM and best supportive care in a UK cohort of adults with CHB. The perspective of the cost-effectiveness analysis was that of the NHS and personal social services. A Markov state transition model was constructed, informed by a systematic search of the literature to identify source material on the natural history, epidemiology and treatment of CHB. Interventions were evaluated against their closest comparator (for PEG this is IFN, and for ADV this is LAM). In addition, the cost-effectiveness of sequential treatment scenarios was modelled. RESULTS: A total of 1086 references to clinical effectiveness studies were identified, of which seven fully published RCTs and one systematic review met the inclusion criteria. Four of the RCTs evaluated the effectiveness of ADV and three reported results for PEG. In addition, a conference abstract was included reporting interim results from an on-going Phase II RCT of ADV in combination with LAM. The published trials were of good quality, although details of randomisation and allocation of concealment were poorly reported. ADV was significantly more effective than placebo. Response rates were in the range 21-51% compared with 0%, respectively. For patients resistant to LAM, response rates were significantly higher for those treated with ADV in addition to on-going LAM (35-85%) than those who continued on LAM with placebo (0-11%). Significant alanine aminotransferase (ALT) reductions to normal levels were observed in all studies. For treatment-naive patients, seroconversion rates were 12-14% for ADV compared with 6% for placebo (statistically significant), rates were higher for LAM-resistant patients who received ADV in addition to on-going LAM (8%) than those who continued on LAM with placebo (2%) (no significance value was reported), and rates were higher for LAM-resistant patients who switched to ADV than those who continued on LAM with placebo (11 versus 0%, respectively; not statistically significant). HBsAg loss or seroconversion was observed in less than 5% of patients taking ADV. Two ADV studies reported changes in liver histology. In general, histological improvement and necroinflammatory activity/fibrosis scores were significantly better in ADV groups than in placebo groups. Dose discontinuations for safety reasons were low for patients receiving ADV. With the exception of headache, the most commonly reported adverse events were often seen in the placebo groups in similar proportions to the ADV groups, with different trials reporting conflicting results. PEG/LAM dual therapy and PEG monotherapy were similar in effect on HBV DNA and ALT levels, and both were significantly superior to LAM monotherapy. Response rates were higher for HBeAg-negative patients than for HBeAg-positive patients. HBeAg seroconversion rates at follow-up were significantly higher for PEG monotherapy patients than for those receiving either a combination of PEG and LAM or LAM monotherapy (32, 27 and 19%, respectively). For the comparison between PEG and IFN-2a, there was a significant difference in the combined outcome of ALT normalisation, HBV DNA response and HBeAg seroconversion at follow-up (24 versus 12%, respectively). Changes in liver histology were reported by two studies. There was no statistically significant difference in histological improvement between the PEG monotherapy groups, the LAM monotherapy groups and the dual therapy groups. Two PEG trials reported small percentages (up to 5%) of HBsAg loss or seroconversion among patients receiving PEG either as monotherapy or in combination with LAM, but no HBsAg loss or seroconversion was reported in those receiving LAM monotherapy. Health-related quality of life (HRQoL) scores, as measured by the Short Form with 36 Items, decreased during treatment, but returned to at least baseline levels at follow-up (based on unpublished data). For HBeAg-positive patients, there were no significant differences in scores between treatment groups. Dose discontinuations for safety reasons were significantly higher for patients receiving PEG than for patients receiving LAM monotherapy. The most commonly reported adverse events in the PEG studies were headache, pyrexia, fatigue, myalgia and alopecia. Only one fully published economic evaluation was identified, reporting a US cost-effectiveness study of ADV as salvage therapy for chronic hepatitis B with LAM resistance. A Markov model was used to estimate cost-effectiveness of interferon alfa (6-12 months), LAM and LAM followed by ADV when resistance occurs. ADV generated the most (undiscounted) life-years, but at highest costs, with an incremental cost-effectiveness ratio (ICER) of US$14,204 per life-year gained. Using our model, incremental cost per QALY estimates (baseline cohort of all patients) were: 5994 pounds for IFN compared with best supportive care, 6119 pounds for PEG compared with IFN, 3685 pounds for LAM compared with best supportive care, and 16,569 pounds for ADV compared with LAM. Incremental cost per QALY estimates (HBeAg-positive patients only) were: 7936 pounds for IFN (24 weeks) compared with best supportive care, 16,166 pounds for PEG (48 weeks) compared with IFN (24 weeks), 3489 pounds for LAM compared with best supportive care, and 15,289 pounds for ADV compared with LAM. Incremental cost per QALY estimates (HBeAg-negative patients only) were: 3922 pounds for IFN (48 weeks) compared with best supportive care, 2162 pounds for PEG (48 weeks) compared with IFN (24 weeks), 4131 pounds for LAM compared with best supportive care, and 18,620 pounds for ADV compared with LAM. For the sequential treatment strategies, incremental cost per QALY estimates ranged from 3604 pounds (IFN followed by LAM versus IFN alone) to 11,402 pounds (IFN followed by LAM with adefovir salvage versus IFN followed by LAM). In all of these cases, the ICERs are well within the range that would conventionally be regarded as being cost-effective. The probabilistic sensitivity analysis found that LAM is a cost-effective option at lower willingness-to-pay thresholds for health outcomes, but as the threshold is increased adefovir is increasingly likely to be the optimal intervention. Where a willingness-to-pay threshold of above 10,000 pounds per QALY is employed, PEG is highly likely to be the optimal intervention compared with IFN (based on a cohort of HBeAg-positive and -negative patients). Interferon alfa (non-pegylated or pegylated) followed by LAM would be the optimal strategy at lower willingness-to-pay thresholds. As the threshold increases, the sequential treatment strategy of PEG followed by LAM with adefovir added as salvage therapy is increasingly likely to be the optimal intervention. CONCLUSIONS: ADV and PEG are associated with significant improvements in a number of biochemical, virological and histological outcomes in both HBeAg-positive and -negative patients. For a small proportion of patients this is associated with resolution of infection. For another proportion it leads to remission and a reduced risk of progressing to cirrhosis, hepatocellular carcinoma, liver transplant and death. For others who do not respond or who relapse, retreatment with another agent is necessary. The results of our cost-effectiveness analysis demonstrate that incremental costs per QALY for a range of comparisons were between 5994 pounds and 16,569 pounds and within the range considered by NHS decision-makers to represent good value for money. When subjected to sensitivity analysis, most costs per QALY estimates remained under 30,000 pounds. Further RCT evidence of the effectiveness of anti-viral treatment is required, particularly for subgroups of patients with different genotypes, patients with cirrhosis, patients from different ethnic groups, patients with co-infections (e.g. HIV, HCV) and co-morbidities, liver transplant patients and children and adolescents.

Adenine↗
PubMed2005

Systematic review of the Sugarbaker procedure for pseudomyxoma peritonei.

BACKGROUND: Pseudomyxoma peritonei, a rare progressive disease process within the peritoneum, is characterized by an abundance of mucinous fluid; if left untreated, the condition is fatal. The aim of this article is to assess the clinical effectiveness and costs of the Sugarbaker procedure for pseudomyxoma peritonei. METHODS: A systematic review of the literature up to April 2004 was undertaken, with modelling of costs. RESULTS: Five retrospective case-series reports met the inclusion criteria. Survival after operation was approximately 95 per cent at 2 years and 60-68 per cent at 10 years, with 41-52 per cent of patients having no evidence of disease at the end of follow-up. A Monte Carlo simulation model estimated the marginal cost for one patient over a maximum of 5 years to be about pound 9700 (standard deviation pound 1300). CONCLUSION: Evidence of the effectiveness of the Sugarbaker procedure for pseudomyxoma peritonei is limited in quantity and quality, but suggests there may be some benefit for patients. The marginal cost of the operation is about pound 9700, provided that trained and experienced staff are available to perform the procedure.

Costs and Cost Analysis↗
PubMed2005

Topical corticosteroids for atopic eczema: clinical and cost effectiveness of once-daily vs. more frequent use.

BACKGROUND: Topical corticosteroids remain the mainstay of treatment for atopic eczema, yet there is uncertainty over the frequency of their use in terms of clinical and cost effectiveness. OBJECTIVES: To assess the clinical and cost effectiveness of once-daily vs. more frequent use of same-potency topical corticosteroids in atopic eczema. METHODS: A systematic review of the clinical and cost-effectiveness literature was undertaken, together with a cost-minimization analysis. RESULTS: The review identified a sparse literature, comprising one previous systematic review and 10 randomized controlled trials (RCTs). No published cost-effectiveness studies were identified. RCTs were focused on potent topical corticosteroids (eight RCTs), with no trials (RCTs/controlled clinical trials) identified on mild potency products. There was broad heterogeneity in trial methods, and therefore we considered outcomes according to: (i) at least a good response or 50% improvement, and (ii) eczema rated as cleared or controlled. Studies found little difference between once-daily and more frequent use of topical corticosteroids. The literature on moderately potent and potent corticosteroids offered no basis for favouring once-daily or more frequent use, although some significant differences favouring twice-daily treatment were identified. One RCT on very potent products favoured three times daily use on the basis of clinical response, but reported no difference in the numbers with at least a good response. Given the similar outcomes seen in clinical effectiveness a cost-minimization approach was adopted to consider cost effectiveness, in order to identify the least-cost option. However, cost-minimization analysis proved complex due to wide variations in product price, with the relative cost of product comparisons by frequency proving the most important factor in determining the least-cost alternative. CONCLUSIONS: This review has not identified any clear differences in outcomes between once-daily and more frequent application of topical corticosteroids. We would encourage prescribing clinicians to consider the once-daily use of topical corticosteroids when making treatment decisions for patients with atopic eczema. However, we find that the literature on clinical effectiveness is limited and a broader understanding of compliance and phobia associated with topical steroids is needed to inform on this issue.

Administration, Cutaneous↗
PubMed2005

Clinical effectiveness and cost-effectiveness of immediate angioplasty for acute myocardial infarction: systematic review and economic evaluation.

OBJECTIVES: To review the clinical evidence comparing immediate angioplasty with thrombolysis, and to consider whether it would be cost-effective. DATA SOURCES: Electronic databases. Experts in the field. REVIEW METHODS: For clinical effectiveness, a comprehensive review of randomised control trials (RCTs) was used for efficacy, and a selection of observational studies such as case series or audit data used for effectiveness in routine practice. RCTs of thrombolysis were used to assess the relative value of prehospital and hospital thrombolysis. Observational studies were used to assess the representativeness of patients in the RCTs, and to determine whether different groups have different capacity to benefit. Clinical effectiveness was synthesised through a narrative review with full tabulation of results of all included studies and a meta-analysis to provide a precise estimate of absolute clinical benefit. Consideration was given to the effect of the growing use of stents. The economic modelling adopted an NHS perspective to develop a decision-analytical model of cost-effectiveness focusing on opportunity costs over the short term (6 months). RESULTS: The results were consistent in showing an advantage of immediate angioplasty over hospital thrombolysis. The updated meta-analysis showed that mortality is reduced by about one-third, from 7.6% to 4.9% in the first 6 months, and by about the same in studies of up to 24 months. Reinfarction is reduced by over half, from 7.6% to 3.1%. Stroke is reduced by about two-thirds, from 2.3% with thrombolysis to 0.7% with percutaneous coronary intervention (PCI), with the difference being due to haemorrhagic stroke. The need for coronary artery bypass graft is reduced by about one-third, from 13.2% to 8.4%. Caution is needed in interpreting some of the older trials, as changes such as an increase in stenting and the use of the glycoprotein IIb/IIa inhibitors may improve the results of PCI. There is little evidence comparing prehospital thrombolysis with immediate PCI. Research on thrombolysis followed by PCI, known as 'facilitated PCI', is underway, but results are not yet available. Trials may be done in select centres and results may not be as good in lower volume centres, or out of normal working hours. In addition, much of the marginal mortality benefit of PCI over hospital thrombolysis may be lost if door-to-balloon time were more than an hour longer than door-to-needle time. Conversely, within the initial 6 hours, the later patients present, the greater the relative advantage of PCI. Results suggest that PCI is more cost-effective than thrombolysis, providing additional benefits in health status at some extra cost. In the longer term, the cost difference is expected to be reduced because of higher recurrence and reintervention rates among those who had thrombolysis. CONCLUSIONS: If both interventions were routinely available, the economic analysis favours PCI, given the assumptions of the model. However, very few units in England could offer a routine immediate PCI service at present, and there would be considerable resource implications of setting up such services. Without a detailed survey of existing provision, it is not possible to quantify the implications, but they include both capital and revenue: an increase in catheter laboratory provision and running costs. The greatest problem would be staffing, and that would take some years to resolve. A gradual incrementalist approach based on clinical networks, with transfer to centres able to offer PCI, may be used. In rural areas, one option may be to promote an increase in prehospital thrombolysis, with PCI for thrombolysis failures. There is a need for data on the long-term consequences of treatment, the quality of life of patients after treatment, and the effects of PCI following thrombolysis failure.

Angioplasty↗
PubMed2005

Regulated deficit irrigation (RDI) to save water and improve Sauvignon Blanc quality?

With a fast change of land use in Marlborough from extensive pastoral farming to intensive irrigated viticulture, a need has risen to investigate the sustainable use of the available water. In 2001 a 5 ha irrigation research project was installed in a Marlborough Sauvignon Blanc vineyard. Irrigation treatments installed were control (compensate 100% for crop evapotranspiration (ET(O)), 80%, 70% and 60% of ET(O). During the two years that the Regulated Deficit Irrigation (RDI) trial has run so far, very different climatic conditions created much greater differences in yield and vegetative growth, than up to 40% reduction in irrigation, none of which were significant. The use of sap flow in the vines has been fine-tuned and is now giving reliable results on which to base vine water need.

Agriculture↗
PubMed2004

Magnetic-field-induced nematic-columnar phase transition in aqueous suspensions of goethite (alpha-FeOOH) nanorods.

Colloidal aqueous suspensions of goethite lath-shaped nanorods form nematic and isotropic phases. We show that they also display a 2D rectangular (c2mm) columnar phase at volume fractions phi larger than 15%. Interestingly, the nematic-columnar first-order transition can also be triggered by applying to the nematic phase a magnetic field of intensity decreasing with phi (1 T at 8.5%; 0.5 T at 12%). Single domains of the columnar phase were thus produced and their structure investigated by synchrotron x-ray scattering. This magnetic-field-induced transition is fully reversible and reproducible.

Journal Article↗
PubMed2004

Physical properties of aqueous suspensions of goethite (alpha-FeOOH) nanorods. Part I: In the isotropic phase.

Depending on volume fraction, aqueous suspensions of goethite (alpha-FeOOH) nanorods form a liquid-crystalline nematic phase (above 8.5%) or an isotropic liquid phase (below 5.5%). In this article, we investigate by small-angle X-ray scattering, magneto-optics, and magnetometry the influence of a magnetic field on the isotropic phase. After a brief description of the synthesis and characterisation of the goethite nanorod suspensions, we show that the disordered phase becomes very anisotropic under a magnetic field that aligns the particles. Moreover, we observe that the nanorods align parallel to a small field (< 350 mT), but realign perpendicular to a large enough field (> 350 mT). This phenomenon is interpreted as due to the competition between the influence of the nanorod permanent magnetic moment and a negative anisotropy of magnetic susceptibility. Our interpretation is supported by the behaviour of the suspensions in an alternating magnetic field. Finally, we propose a model that explains all experimental observations in a consistent way.

Journal Article↗
PubMed2004

Physical properties of aqueous suspensions of goethite (alpha-FeOOH) nanorods. Part II: In the nematic phase.

At volume fractions larger than 8.5%, aqueous suspensions of lath-like goethite (alpha-FeOOH) nanorods form a lyotropic nematic phase. In this article, we first discuss the nematic ordering within statistical-physics models of the isotropic/nematic phase transition. We then describe the influence of a magnetic field on the nematic phase. Because the nanorods bear permanent magnetic moments, the nematic suspensions have dipolar order and very low Frederiks thresholds. Moreover, the nematic phase aligns parallel to a small magnetic field but realigns perpendicular to a high field because of a competition between the permanent moments of the nanorods and their negative anisotropy of magnetic susceptibility. This magneto-optical study of the nematic phase is completely consistent with that of the isotropic phase of the same suspensions published in Part I (this issue, p. 291). Besides, we demonstrate the field-induced biaxiality of a nematic single domain aligned perpendicular to the field. We also describe here preliminary experiments where an a.c. electric field is applied to the nematic phase. Both field amplitude and frequency were found to control the alignment direction and homeotropic-to-planar alignment transitions were observed. From this data, simple models were used to estimate some physical constants of the nematic phase.

Journal Article↗
PubMed2004

Clinical effectiveness and costs of the Sugarbaker procedure for the treatment of pseudomyxoma peritonei.

OBJECTIVES: This systematic review examines the clinical and cost-effectiveness of the Sugarbaker procedure for treating pseudomyxoma peritonei (PMP) and the costs of the procedure in the UK. DATA SOURCES: Electronic databases, bibliographies of related papers and experts in the field were used as sources for English language studies available up to September 2002. REVIEW METHODS: Evidence of the clinical effectiveness of the Sugarbaker procedure for PMP was synthesised through a narrative review with full tabulation of results of all included studies. The economic modelling used a Monte-Carlo simulation model populated with UK price data to estimate likely UK costs. RESULTS: Five retrospective case-series reports assessing the Sugarbaker procedure met the inclusion criteria for the review, although they were found to be of poor quality when judged against standard criteria for assessing methodological standard. There appears to be some benefit for people with PMP who undergo treatment with the Sugarbaker procedure. Commonly reported complications of the Sugarbaker procedure were anastomotic leaks, fistula formation, wound infection, small bowel perforations/obstructions and pancreatitis. One costing study of poor methodological quality and set in the USA was found. This study, together with UK unit price data and expert advice, was used to populate a Monte-Carlo simulation model to estimate the marginal cost of operating a service to provide treatment for PMP using the Sugarbaker technique rather than standard treatment. The results of the Monte-Carlo simulation model showed that the cost for one patient over a maximum of 5 years would be about 9700 British pounds, with a standard deviation of about 1300 British pounds (although costs incurred in setting up the specific service or training the staff were not included). The US study showed a ten-fold higher cost. The Monte-Carlo analysis showed that the variation around the mean was not very high. The most likely factor influencing the variation of the costs was the length of procedure. No sensitivity analysis could be done of the alternative treatment. CONCLUSIONS: The economic results should be seen as merely an example of the likely marginal costs of the Sugarbaker procedure, as more information about the current alternative is required. Trained and experienced staff are required to implement the procedure and inevitably time and cost will be involved in developing the appropriate teams. Although the procedure requires some specialist equipment and maintenance, such as smoke evacuators, these should have limited effect on setting up the service. PMP is a relatively rare condition with approximately 50 new cases per year in the UK and the impact of an increase in the demand for services should be limited. Evidence is needed for the effectiveness of maximal cytoreductive surgery compared with surgical debulking, using different intraoperative intraperitoneal chemotherapy strategies, and for the effectiveness of treatments in patients who have residual disease following maximal efforts at cytoreduction. Further research involving high-quality prospective cohort studies with economic evaluations would be valuable.

Adult↗
PubMed2004

Clinical and cost-effectiveness of once-daily versus more frequent use of same potency topical corticosteroids for atopic eczema: a systematic review and economic evaluation.

OBJECTIVES: To assess the clinical and cost-effectiveness of once-daily use of topical corticosteroids versus more frequent use of same-potency topical corticosteroids in the treatment of people with atopic eczema. DATA SOURCES: Electronic databases. Bibliographies of included studies and related papers. Experts in the field. Manufacturer submissions to the National Institute for Clinical Excellence. REVIEW METHODS: Studies were assessed for inclusion according to predefined criteria by two reviewers. Data extraction and quality assessment were undertaken by one reviewer and checked by a second reviewer. Clinical effectiveness data were synthesised through a narrative review with full tabulation of results. RESULTS: One RCT comparing moderately potent corticosteroids, eight RCTs comparing potent corticosteroids and one RCT comparing very potent corticosteroids were included. No RCTs or CCTs of mild corticosteroids were eligible. Most RCTs were of poor methodological quality, although two were judged to be of good quality. The only study that compared moderately potent corticosteroids found no significant difference between once- and twice-daily application. For potent corticosteroids, some statistically significant differences in numbers of patients responding to treatment were identified favouring twice-daily treatment, but these were inconsistent between physician and patient assessment and outcomes selected for analysis. Two studies found a significant improvement in some symptoms with once-daily mometasone furoate compared with twice-daily application of a different active compound, while a third study found no significant differences. One good-quality study favoured twice-daily application of fluticasone propionate ointment, while other studies found no significant difference or an improvement in one symptom but not others. The only study comparing very potent corticosteroids found a statistically significant difference in comparative clinical response in favour of three-times daily treatment, but no difference in number of patients with at least a good response. There appears to be little difference in the frequency or severity of short-term events, however data are limited. No published economic evaluations were identified. Given findings on clinical effectiveness, where outcomes from the comparators are similar, the relative cost-effectiveness of once-daily versus more frequent application of topical corticosteroids becomes a case of cost-minimisation, where the least-cost alternative should be favoured, all else being equal. Topical corticosteroid products included in this review have a wide variation in price; the cost per 30 g/30 ml varies between GBP0.60 and GBP4.88. Specific decisions on the least-cost alternative, between once-daily and more frequent application of products, will be determined by the relative price of the products being compared. Where patients can be appropriately prescribed once-daily treatment of a similarly priced product, a reduction in the quantity of topical corticosteroid used will be expected. However, issues related to pack size for prescribed products and subsequent waste (unused product) could easily erode any potential saving. The potential cost-savings on prescribed products are very small at a patient level; although given the large numbers of patients with atopic eczema, cost savings in theory could be substantial. The presence of specifically marketed 'once-daily' topical corticosteroids, which are relatively expensive (per unit price), may result in additional costs should there be a general recommendation in favour of once-daily use of topical corticosteroids, compared to more frequent use. CONCLUSIONS: The literature is very limited; that available indicates the clinical effectiveness of once-daily and more frequent application of potent topical corticosteroids is very similar, but it does not offer a basis for favouring either option. The cost-effectiveness of once-daily versus more frequent use will depend on the generalisability of the findings to the specific treatment decision and the relative product prices. The trials included in this review generally refer to moderate to severe atopic eczema, whereas most patients have mild disease, and furthermore most of the included trials report on potent topical corticosteroids (eight of 10 RCTs); therefore the generalisability of the findings is limited. Further research is required on the clinical and cost-effectiveness of once-daily versus more frequent use of same potency corticosteroids, specifically on mild potency products for mild to moderate atopic eczema. Outcomes should include quality of life and compliance.

Administration, Topical↗
PubMed2004

Preventing drug-resistant tuberculosis with a fixed dose combination of isoniazid and rifampin.

SETTING: Los Angeles County Department of Health Services. OBJECTIVE: To determine how well a self-administered fixed dose combination of isoniazid and rifampin (CombinedHR) prevents acquired drug resistance to Mycobacterium tuberculosis despite treatment interruptions. DESIGN: Self-administered CombinedHR was given to approximately 75% of patients and directly observed therapy or separate drugs to 25%. Three quarters of the patients completed the prescribed treatment. We determined 1) how many patients had two drug-susceptible cultures 3 or more months apart as a measure of drug-susceptible failure or relapse, 2) how many patients whose initial culture was drug-susceptible had a subsequent drug-resistant culture as a measure of acquired drug resistance, and 3) what treatment regimen was taken by each patient who developed acquired drug resistance. RESULTS: Among 5337 drug-susceptible tuberculosis patients who were known or presumed to be human immunodeficiency virus (HIV) negative, 152 (2.84%) treatment failures or relapses occurred, of which 25 (0.47%) developed acquired drug resistance. Among approximately 4000 cases taking CombinedHR and primarily CombinedHR, drug resistance occurred in only eight cases (0.2%), and a total of 12 cases (0.3%) when patients with indeterminate treatment histories were added. CONCLUSIONS: Treatment with self-administered CombinedHR results in minimal acquired drug resistance in HIV-seronegative tuberculosis cases despite modest rates of incomplete treatment.

Antibiotics, Antitubercular↗
PubMed2002

Outstanding magnetic properties of nematic suspensions of goethite (alpha-FeOOH) nanorods.

Aqueous suspensions of goethite (alpha-FeOOH) nanorods form a mineral lyotropic nematic phase that aligns in a very low magnetic field (20 mT for samples 20 microm thick). The particles orient along the field direction at intensities smaller than 350 mT, but they reorient perpendicular to the field beyond 350 mT. This outstanding behavior is also observed in the isotropic phase which has a very strong magnetic-field induced birefringence that could be interesting for applications. We interpret these magnetic effects as resulting from a competition between a nanorod remanent magnetic moment and a negative anisotropy of its magnetic susceptibility.

Journal Article↗
PubMed2001

Swollen liquid-crystalline lamellar phase based on extended solid-like sheets.

Ordering particles at the nanometre length scale is a challenging and active research area in materials science. Several approaches have so far been developed, ranging from the manipulation of individual particles to the exploitation of self-assembly in colloids. Nanometre-scale ordering is well known to appear spontaneously when anisotropic organic moieties form liquid-crystalline phases; this behaviour is also observed for anisotropic mineral nanoparticles resulting in the formation of nematic, smectic and hexagonal mesophases. Here we describe a lyotropic liquid-crystalline lamellar phase comprising an aqueous dispersion of planar solid-like sheets in which all the atoms involved in a layer are covalently bonded. The spacing of these phosphatoantimonate single layers can be increased 100-fold, resulting in one-dimensional structures whose periodicity can be tuned from 1.5 to 225 nanometres. These highly organized materials can be mechanically or magnetically aligned over large pH and temperature ranges, and this property can be used to measure residual dipolar couplings for the structure determination of biomolecules by liquid-state NMR. We also expect that our approach will result in the discovery of other classes of mineral lyotropic lamellar phases.

Acids↗