Desmond B. Williams

Rosemary and Cancer Prevention: Preclinical Perspectives

Colorectal cancer is the second leading cause of cancer death in Australia. Nutrition, particularly intake of vegetables and certain plant components, has been reported to have a major role in cancer risk reduction. Recently, there has been a growing research interest in rosemary, a common household plant grown in many parts of the world. This study aims to review scientific evidence from all studies, published from 1996 to March 2010 that examined the protective effects of rosemary on colorectal cancer and other types of cancer. Literature evidence from animal and cell culture studies demonstrates the anticancer potential of rosemary extract, carnosol, carnosic acid, ursolic acid, and rosmarinic acid. No evidence for other rosemary constituents was found. The reported anticancer properties were found to arise through the molecular changes in the multiple-stage process of cancer development, which are dose related and not tissue or species specific. This is evidenced by the ability of rosemary to suppress the development of tumors in several organs including the colon, breast, liver, stomach, as well as melanoma and leukemia cells. The results suggested that the different molecular targets modulated by rosemary and its active constituents are useful indicators of success in clinical cancer chemo-prevention trials.

Medication-overuse headache and opioid-induced hyperalgesia: A review of mechanisms, a neuroimmune hypothesis and a novel approach to treatment

Introduction Patients with chronic headache who consume large amounts of analgesics are often encountered in clinical practice. Excessive intake of analgesics is now considered to be a cause, rather than simply a consequence, of frequent headaches, and as such the diagnosis “medication-overuse headache” (MOH) has been formulated. Despite the prevalence and clinical impact of MOH, the pathophysiology behind this disorder remains unclear and specific mechanism-based treatment options are lacking. Discussion Although most acute headache treatments have been alleged to cause MOH, here we conclude from the literature that opioids are a particularly problematic drug class consistently associated with worsening headache. MOH may not be a single entity, as each class of drug implicated may cause MOH via a different mechanism. Recent evidence indicates that chronic opioid administration may exacerbate pain in the long term by activating toll-like receptor-4 on glial cells, resulting in a pro-inflammatory state that manifests clinically as increased pain. Thus, from the available evidence it seems opioid-overuse headache is a phenomenon similar to opioid-induced hyperalgesia, which derives from a cumulative interaction between central sensitisation, due to repeated activation of nociceptive pathways by recurrent headaches, and pain facilitation due to glial activation. Conclusion Treatment strategies directed at inhibiting glial activation may be of benefit alongside medication withdrawal in the management of MOH.

Low-dose endotoxin potentiates capsaicin-induced pain in man: evidence for a pain neuroimmune connection

Despite the wealth of evidence in animals that immune activation has a key role in the development and maintenance of chronic pain, evidence to support this in humans is scant. We have sought such evidence by examining the effect of a subtle immunological stimulus, low dose intravenous endotoxin, on the allodynia, hyperalgesia, flare and pain produced by intradermal capsaicin in healthy volunteers. Here we provide evidence of immune priming of this neuropathic-like pain response in humans. Specifically, in 12 healthy volunteers, activation of Toll-Like Receptor 4 by endotoxin (0.4ng/kg IV) caused significant 5.1-fold increase in the 90-min integral of areas of capsaicin-induced allodynia (95% CI 1.3-9.1), 2.2-fold increase in flare (95% CI 1.9-2.6) and 1.8-fold increase in hyperalgesia (95% CI 1.1-2.5) following 50μg intradermal capsaicin injected into the forearm 3.5h after endotoxin. These data demonstrate clinically a significant role for the neuroimmune pain connection in modifying pain, thus providing evidence that immune priming may produce pain enhancement in humans and hence offer a novel range of pharmacological targets for anti-allodynics and/or analgesics. Additionally, the simplicity of the model makes it suitable as a test-bed for novel immune-targeted pain therapeutics.

Estimating the sorption of pharmaceuticals based on their pharmacological distribution

Pharmaceuticals released into aquatic systems are expected to sorb to sediments to varying degrees. Their sorption is likely to influence their fate and, ultimately, the risk they pose to aquatic organisms. This has led to the European Medicines Agency requiring an assessment of affinity to solids, using batch sorption methods, for the environmental risk assessment (ERA) of new human medicines. However, a large body of data is generated before pharmaceuticals are released onto the market, including their extent of distribution throughout the human body, measured by the volume of distribution (VD). In the present study, batch sorption experiments were undertaken using 12 different soils and sediments to determine whether VD was a good indicator of experimental Kd values for 21 pharmaceuticals. The r2 values obtained from the regressions ranged from 0.39 to 0.76 (with a median value of 0.5) and all regressions were found to be significant. The use of this more comprehensive set of soils and sediments was consistent with previous studies comparing VD and Kd, despite the Kd values of the selected pharmaceuticals varying greatly between soils. The relationship between Kd and VD was greatly improved when zwitterionic antibiotics and carbamazepine were not included, possibly due to complex sorption or pharmacokinetic behavior. There are likely to be a number of factors affecting the sorption of pharmaceuticals that cannot be explained by VD. However, further work may elucidate how these factors can be accounted for, enabling VD to be effectively used to facilitate the ERA of human pharmaceuticals with already available information.

Food, gastrointestinal pH, and models of oral drug absorption

Graphical abstract Figure. No caption available. Abstract This article reviews the major physiological and physicochemical principles of the effect of food and gastrointestinal (GI) pH on the absorption and bioavailability of oral drugs, and the various absorption models that are used to describe/predict oral drug absorption. The rate and extent of oral drug absorption is determined by a complex interaction between a drug’s physicochemical properties, GI physiologic factors, and the nature of the formulation administered. GI pH is an important factor that can markedly affect oral drug absorption and bioavailability as it may have significant influence on drug dissolution & solubility, drug release, drug stability, and intestinal permeability. Different regions of the GI tract have different drug absorptive properties. Thus, the transit time in each GI region and its variability between subjects may contribute to the variability in the rate and/or extent of drug absorption. Food‐drug interactions can result in delayed, decreased, increased, and sometimes un‐altered drug absorption. Food effects on oral absorption can be achieved by direct and indirect mechanisms. Various models have been proposed to describe oral absorption ranging from empirical models to the more sophisticated “mechanism‐based” models. Through understanding of the physicochemical and physiological rate‐limiting factors affecting oral absorption, modellers can implement simplified population‐based modelling approaches that are less complex than whole‐body physiologically‐based models but still capture the essential elements in a physiological way and hence will be more suited for population modelling of large clinical data sets. It will also help formulation scientists to better predict formulation performance and to develop formulations that maximize oral bioavailability.

Efficacy of butyrate analogues in HT‐29 cancer cells

1. Butyrate is a well known product of starch fermentation by colonic bacteria and is of interest owing to its ability to induce in vitro apoptosis and cell differentiation, as well as to inhibit cell growth in colorectal and other cancer cells. Synthetic analogues of butyrate may also possess cellular activities in a variety of cultured cells. The aim of the present study was to evaluate the effects of butyrate analogues on apoptosis, proliferation and histone deacetylase (HDAC) activity in HT‐29 colorectal cancer cells. In addition, the effects of these analogues on lactate dehydrogenase leakage, as a measure of non‐specific cytotoxicity, were evaluated in HT‐29 cells.

Development and Optimization of Micro/Nanoporous Osmotic Pump Tablets

Micro/nanoporous osmotic pump tablets coated with cellulose acetate containing polyvinylpyrolidone (PVP) as pore formers were fabricated. Propranolol hydrochloride was used as a model drug in this study. Formulation optimization based on USP 31 requirements was conducted following a central composite design using a two-level factorial plan involving two membrane variables (pore former and coating levels). Effect of molecular weight of pore former (PVP K30 and PVP K90) was also evaluated. Responses of drug release to the variables were analyzed using statistical software (MINITAB 14). Scanning electron microscopy and atomic force microscopy showed that the pores formed by PVP. The drug release was dependent on the molecular weight and concentration of PVP and the level of coating. The results showed that acceptable 12-h profile could be achieved with only specific range of PVP K30-containing membrane at the defined membrane thickness. However, satisfactory 24-h profile could be accomplished by both PVP K30 and PVP K90-containing membrane at the range and membrane thickness tested. Preparation and testing of the optimized formulation showed a good correlation between predicted and observed values.

The Effects of Pregabalin and the Glial Attenuator Minocycline on the Response to Intradermal Capsaicin in Patients with Unilateral Sciatica

Background Patients with unilateral sciatica have heightened responses to intradermal capsaicin compared to pain-free volunteers. No studies have investigated whether this pain model can screen for novel anti-neuropathic agents in patients with pre-existing neuropathic pain syndromes. Aim This study compared the effects of pregabalin (300 mg) and the tetracycline antibiotic and glial attenuator minocycline (400 mg) on capsaicin-induced spontaneous pain, flare, allodynia and hyperalgesia in patients with unilateral sciatica on both their affected and unaffected leg. Methods/Results Eighteen patients with unilateral sciatica completed this randomised, double-blind, placebo-controlled, three-way cross-over study. Participants received a 10 µg dose of capsaicin into the middle section of their calf on both their affected and unaffected leg, separated by an interval of 75 min. Capsaicin-induced spontaneous pain, flare, allodynia and hyperalgesia were recorded pre-injection and at 5, 20, 40, 60 and 90 min post-injection. Minocycline tended to reduce pre-capsaicin injection values of hyperalgesia in the affected leg by 28% (95% CI 0% to 56%). The area under the effect time curves for capsaicin-induced spontaneous pain, flare, allodynia and hyperalgesia were not affected by either treatment compared to placebo. Significant limb differences were observed for flare (AUC) (−38% in affected leg, 95% CI for difference −19% to −52%). Both hand dominance and sex were significant covariates of response to capsaicin. Conclusions It cannot be concluded that minocycline is unsuitable for further evaluation as an anti-neuropathic pain drug as pregabalin, our positive control, failed to reduce capsaicin-induced neuropathic pain. However, the anti-hyperalgesic effect of minocycline observed pre-capsaicin injection is promising pilot information to support ongoing research into glial-mediated treatments for neuropathic pain. The differences in flare response between limbs may represent a useful biomarker to further investigate neuropathic pain. Inclusion of a positive control is imperative for the assessment of novel therapies for neuropathic pain.

Codeine-induced hyperalgesia and allodynia: investigating the role of glial activation

Chronic morphine therapy has been associated with paradoxically increased pain. Codeine is a widely used opioid, which is metabolized to morphine to elicit analgesia. Prolonged morphine exposure exacerbates pain by activating the innate immune toll-like receptor-4 (TLR4) in the central nervous system. In silico docking simulations indicate codeine also docks to MD2, an accessory protein for TLR4, suggesting potential to induce TLR4-dependent pain facilitation. We hypothesized codeine would cause TLR4-dependent hyperalgesia/allodynia that is disparate from its opioid receptor-dependent analgesic rank potency. Hyperalgesia and allodynia were assessed using hotplate and von Frey tests at days 0, 3 and 5 in mice receiving intraperitoneal equimolar codeine (21 mg kg−1), morphine (20 mg kg−1) or saline, twice daily. This experiment was repeated in animals with prior partial nerve injury and in TLR4 null mutant mice. Interventions with interleukin-1 receptor antagonist (IL-1RA) and glial-attenuating drug ibudilast were assessed. Analyses of glial activation markers (glial fibrillary acid protein and CD11b) in neuronal tissue were conducted at the completion of behavioural testing. Despite providing less acute analgesia (P=0.006), codeine induced similar hotplate hyperalgesia to equimolar morphine vs saline (−9.5 s, P<0.01 and −7.3 s, P<0.01, respectively), suggesting codeine does not rely upon conversion to morphine to increase pain sensitivity. This highlights the potential non-opioid receptor-dependent nature of codeine-enhanced pain sensitivity—although the involvement of other codeine metabolites cannot be ruled out. IL-1RA reversed codeine-induced hyperalgesia (P<0.001) and allodynia (P<0.001), and TLR4 knock-out protected against codeine-induced changes in pain sensitivity. Glial attenuation with ibudilast reversed codeine-induced allodynia (P<0.001), and thus could be investigated further as potential treatment for codeine-induced pain enhancement.

A comparison of two formulations of intradermal capsaicin as models of neuropathic pain in healthy volunteers

AIMS To compare the dose-response relationships of two formulations [Tween- or hydroxypropyl-b-cyclodextrin (HP-b-CD)-based] of intradermal capsaicin in healthy volunteers and to assess the effect of potential covariates of response. One, 10, 30 and 100 microg in 10 ml were compared for the outcomes of flare, spontaneous pain, mechanical allodynia and hyperalgesia in eight healthy men and eight healthy women. RESULTS The formulations produced comparable responses at doses 1, 10 and 30 microg, but in all parameters the response was less at 100 microg with the Tween formulation.Mean area for hyperalgesia was 9 cm(2) [95% confidence interval (CI) 5, 13] higher with the HP-beta-CD formulation. Flare area was 5 cm(2) (95% CI 8, 13) greater with the HP-beta-CD formulation. There was a significant difference between pain responses from the injection site on the upper forearm compared with the lower forearm on all four pain assessments. In contrast, significant differences were seen in pain response between nondominant and dominant arm for flare, allodynia and hyperalgesia but not for spontaneous pain. A significant difference in sex was seen only for hyperalgesia. The nominal 100-microg dose of the Tween formulation contained only 39% of label strength in the aqueous phase, which may explain the lower pharmacodynamic response. CONCLUSION The formulations are comparable over the dose range 1-30 microg. The significantly lower pain response at the 100 microg dose in the Tween compared with the HP-beta-CD formulation is likely to be due to limitations in solubility at the 100 microg level. Given the greater ease of formulation and the superior dose-response relationship, the HP-beta-CD formulation is preferable for use in the model in future studies.