Overcoming barriers to implementing precision dosing with 5-fluorouracil and capecitabine.

Despite advances in targeted cancer therapy, the fluoropyrimidines 5-fluorouracil (5FU) and capecitabine continue to play an important role in oncology. Historically, dosing of these drugs has been based on body surface area. This approach has been demonstrated to be an imprecise way to determine the optimal dose for a patient. Evidence in the literature has demonstrated that precision dosing approaches, such as DPD enzyme activity testing and, in the case of intravenous 5FU, pharmacokinetic-guided dosing, can reduce toxicity and yield better patient outcomes. However, despite the evidence, there has not been uniform adoption of these approaches in the clinical setting. When a drug such as 5FU has been used clinically for many decades, it may be difficult to change clinical practice. With the aim of facilitating change of practice, issues and barriers to implementing precision dosing approaches for 5FU and capecitabine are identified and discussed with possible solutions proposed.

Pharmacokinetics in neonatal prescribing: evidence base, paradigms and the future.

Paediatric patients, particularly preterm neonates, present many pharmacological challenges. Due to the difficulty in conducting clinical trials in these populations dosing information is often extrapolated from adult populations. As the processes of absorption, distribution, metabolism and excretion of drugs change throughout growth and development extrapolation presents risk of over or underestimating the doses required. Information about the development these processes, particularly drug metabolism pathways, is still limited with weight based dose adjustment presenting the best method of estimating pharmacokinetic changes due to growth and development. New innovations in pharmacokinetic research, such as population pharmacokinetic modelling, present unique opportunities to conduct clinical trials in these populations improving the safety and effectiveness of the drugs used. More research is required into this area to ensure the best outcomes for our most vulnerable patients.

Advances in oral nano-delivery systems for colon targeted drug delivery in inflammatory bowel disease: selective targeting to diseased versus healthy tissue.

Colon targeted drug delivery is an active area of research for local diseases affecting the colon, as it improves the efficacy of therapeutics and enables localized treatment, which reduces systemic toxicity. Targeted delivery of therapeutics to the colon is particularly advantageous for the treatment of inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease. Advances in oral drug delivery design have significantly improved the bioavailability of drugs to the colon; however in order for a drug to have therapeutic efficacy during disease, considerations must be made for the altered physiology of the gastrointestinal (GI) tract that is associated with GI inflammation. Nanotechnology has been used in oral dosage formulation design as strategies to further enhance uptake into diseased tissue within the colon. This review will describe some of the physiological challenges faced by orally administered delivery systems in IBD, the important developments in orally administered nano-delivery systems for colon targeting, and the future advances of this research. FROM THE CLINICAL EDITOR: Inflammatory Bowel Disease (IBD) poses a significant problem for a large number of patients worldwide. Current medical therapy mostly aims at suppressing the active inflammatory episodes. In this review article, the authors described and discussed the various approaches current nano-delivery systems can offer in overcoming the limitations of conventional drug formulations.

Paclitaxel and Therapeutic Drug Monitoring with Microsampling in Clinical Practice.

Paclitaxel is an anticancer agent efficacious in various tumors. There is large interindividual variability in drug plasma concentrations resulting in a wide variability in observed toxicity in patients. Studies have shown the time the concentration of paclitaxel exceeds 0.05 µM is a predictive parameter of toxicity, making dose individualization potentially useful in reducing the adverse effects. To determine paclitaxel drug concentration, a venous blood sample collected 24 h following the end of infusion is required, often inconvenient for patients. Alternatively, using a microsampling device for self-sampling would facilitate paclitaxel monitoring regardless of the patient's location. We investigated the feasibility of collecting venous and capillary samples (using a Mitra® device) from cancer patients to determine the paclitaxel concentrations. The relationship between the venous plasma and whole blood and venous and capillary blood (on Mitra®) paclitaxel concentrations, defined by a Passing-Bablok regression, were 0.8433 and 0.8569, respectively. Demonstrating a clinically acceptable relationship between plasma and whole blood paclitaxel concentration would reduce the need to establish new target concentrations in whole blood. However, in this study, comparison of venous and capillary blood using Mitra® for sampling displayed wide confidence intervals suggesting the results from the plasma and whole blood on this device may not be interchangeable.

Measurement of 5- fluorouracil, capecitabine and its metabolite concentrations in blood using volumetric absorptive microsampling technology and LC-MS/MS.

5-fluorouracil (5-FU) and its oral formulation, capecitabine, are widely used in treating a range of malignancies, either alone or in combination with other antineoplastic drugs. Body surface area-based dosing is used for these agents, despite this approach leading to substantial variability in drug exposure and often resulting in either toxicity or treatment failure. Tailoring therapeutic regimens for individual patients using therapeutic drug monitoring (TDM) has been shown to significantly reduce toxicity and improve cancer outcomes. However, for optimum TDM, sample timing is crucial, along with the need for a venepuncture blood sample to obtain the plasma currently used for 5-FU measurement. In addition to complex blood sample handling requirements, large sample volume and frequent sampling required for pharmacokinetic analysis is another barrier to successfully implementing TDM in a healthcare setting. Microsampling is an alternative collection method to venepuncture, which, combined with the now readily available liquid chromatography mass spectrometry (LC-MS/MS) technology, overcomes the plasma-associated issues. It also has the significant advantage of enabling at home and remote sampling, thus facilitating 5-FU TDM in clinical practice. A LC-MS/MS method for simultaneous measurement of capecitabine, 5'-deoxy-5-fluorocytidine, 5'-deoxy-5-fluorouridine and 5-FU using Mitra® microsampling devices for sample collection was developed. A Shimadzu 8060 LC-MS/MS equipped with electrospray ionisation source interface, operated in positive and negative ion modes, with reversed-phase chromatographic separation was employed for sample analysis. Samples were extracted from Mitra® devices using acetonitrile containing stable isotope-labelled internal standards, sonicated, evaporated under vacuum and resuspended in 0.1 % formic acid before injection into the LC-MS/MS. Chromatographic separation was on a Luna Omega Polar C18 (100 × 2.1 mm, 1.6 µm) column with gradient elution of 0.1 % formic acid in water and acetonitrile. Total run time was 5 min, with the injection volume of 1 µL. The intra and inter-day imprecision ranged from 3.0 to 8.1 and 6.3-13.3 % respectively. Accuracy ranged from 95 -114 % for all analytes. Lower limit of quantification with imprecision of < 19 % and accuracy between 89 and 114 % was 0.05 mg/L for 5-FU and 10 µg/L for other analytes. Assays were linear from 0.05 to 50 mg/L for 5-FU and 10-10,000 µg/L for all other analytes. Analytes were stable on Mitra® devices for up to 9 months at room temperature, 2 years at -30 ℃ and 3 days at 50 ℃. The method was successfully applied for the analysis of samples from patients undergoing cancer treatment with 5-FU and capecitabine. Microsampling using volumetric absorptive microsampling proved to be as reliable as conventional blood collection for 5-FU and capecitabine. This sampling technique may lead to less invasive and better-timed sample collection for TDM, supporting dose optimization strategy.

Clinic- and Hospital-Based Home Care, Outpatient Parenteral Antimicrobial Therapy (OPAT) and the Evolving Clinical Responsibilities of the Pharmacist.

Clinic- and hospital-based home care describes models of care where services commonly associated with hospital inpatient care are provided at the patient's home or in an outpatient or community-based clinic. Hospital in the Home (HITH), also termed Hospital at Home (HaH) in parts of Europe and America, is a common and important example of this type of care. Other examples include infusion centers, skilled nursing facilities (particularly in the USA), self-administration models (including home infusion services) and administration through outpatient or community clinics. Different models of HITH care are used internationally and these encompass a wide range of services. Medication administration, particularly outpatient parenteral antimicrobial therapy (OPAT), is an important element in many of these models of care. There is a key role for pharmacists since the provision of medication is integral in this model of patient care outside the hospital setting. Data on the growing importance of HITH and OPAT as well as the administration of medications suited to clinic- and hospital-based home care, including subcutaneous and intramuscular injectables, immunoglobulins and other blood fractions, cancer chemotherapy, total parenteral nutrition, biologicals/biosimilars, vasopressors and enzymes, using differing service models, are described. The pharmacist's role is evolving from that involved primarily with dose preparation and supply of medications. Their clinical expertise in medication management ensures that they are an integral member and leader in these models of care. Their role ensures the safe and quality use of medicines, particularly across transitions of care, with the pharmacist taking on the roles of educator and consultant to patients and health professional colleagues. Activities such as antimicrobial stewardship and ongoing monitoring of patients and outcomes is fundamental to ensure quality patient outcomes in these settings.

Barriers and Challenges in Performing Pharmacokinetic Studies to Inform Dosing in the Neonatal Population.

A number of barriers and challenges must be overcome in order to conduct the pharmacokinetic studies that are urgently needed to inform the selection and dosing of medication in neonates. However, overcoming these barriers can be difficult. This review outlines the common barriers researchers are confronted with, including issues with ethics approval and consent, study design for pharmacokinetic studies and the ability to measure the drug concentrations in the blood samples obtained. Strategies to overcome these challenges are also proposed.

An examination of the cardiovascular effects of an 'Irukandji' jellyfish, Alatina nr mordens.

Irukandji syndrome is usually characterized by delayed severe abdominal, back and chest pain associated with autonomic effects including diaphoresis, hypertension and, in severe cases, myocardial injury and pulmonary oedema. It is most often associated with envenoming by the jellyfish Carukia barnesi, but a number of other jellyfish, including Alatina mordens, are now known to produce Irukandji syndrome. In the present study, nematocyst-derived venom from A. nr mordens (150-250 microg/kg, i.v.) produced a long-lasting pressor effect in anaesthetised rats. This pressor response (250 microg/kg, i.v.) was significantly inhibited by prior administration of the alpha-adrenoceptor antagonist prazosin (200 microg/kg, i.v.) but not by CSL box jellyfish antivenom (300 U/kg, i.v.). A. nr mordens venom 250 microg/kg (i.v.) caused marked increases in plasma adrenaline and noradrenaline concentrations following administration in anaesthetised rats. The venom did not contain appreciable amounts of either adrenaline or noradrenaline. A. nr mordens venom (25 microg/ml) produced a contractile response in rat electrically stimulated vas deferens which was markedly reduced in tissues pre-treated with reserpine (0.1mM) or guanethidine (0.1mM). Sodium dodecyl sulphate (SDS)-PAGE analysis showed that A. nr mordens venom is comprised of multiple protein bands ranging from 10 to 200 kDa. Western blot analysis using CSL box jellyfish antivenom indicated several antigenic proteins in A. nr mordens venom, however, it did not detect all proteins present in the venom. This study characterizes the in vitro and in vivo effects of A. nr mordens venom and indicates that the cardiovascular effects are at least partially mediated by endogenous catecholamine release.

Efficacy of antivenom against the procoagulant effect of Australian brown snake (Pseudonaja sp.) venom: in vivo and in vitro studies.

Snake venom induced consumption coagulopathy (VICC) is a common complication of snake bite due to prothrombin activators or thrombin-like enzymes in the venom. This study aimed to determine the efficacy and dose of antivenom for treating VICC in patients envenomed by brown snakes (Pseudonaja spp.), including in vitro coagulation studies. In serial blood samples from patients with brown snake envenoming, venom and antivenom concentrations were measured using enzyme immunoassays. In vitro mixtures of brown snake venom and antivenom were used to investigate antivenom binding, neutralisation of prothrombin activity, prevention of venom-mediated clotting and effect on thrombin generation parameters using a thrombinoscope. In 27 envenomed patients the median venom concentration was 20 ng/mL (Interquartile range[IQR]:12-44 ng/mL) prior to antivenom and was not detected after antivenom administration, including 9 patients given one vial. In vitro, 200 microg/mL of antivenom bound all free venom at venom concentrations seen in patients. In vitro prothrombinase activity of the venom (using a chromogenic substrate) was not neutralised by antivenom. However, for venom concentrations seen in humans, 100 microg/mL of antivenom prevented venom clotting activity in human plasma and 479 microg/mL neutralised procoagulant venom activity measured by triggering thrombin generation. One vial of antivenom appears to be sufficient to bind and neutralise all venom in patients with severe brown snake envenoming.

Cross-neutralisation of Australian brown and tiger snake venoms with commercial antivenoms: Cross-reactivity or antivenom mixtures?

Recently it has been suggested that the Australian snake antivenoms made by CSL Ltd. are in fact not truly monovalent and may contain antibodies to other snake venoms because the horses are injected with multiple snake venoms. It is unclear to what extent various monovalent antivenoms can neutralise the effect of other venoms, whether this is due to a mixture of antibodies or true cross-reactivity, and whether this has any clinical significance. We aimed to study the immunological and functional properties of brown snake (Pseudonaja spp.) antivenom (BSAV) and tiger snake (Notechis spp.) antivenom (TSAV) against their respective venoms using enzyme immunoassays (EIA) and in vitro clotting studies. There was significant overlap between the two antivenoms with both TSAV and BSAV being detected by EIA on brown snake venom (BSV)-coated and tiger snake venom (TSV)-coated wells, respectively. In a competition EIA, increasing amounts of immunoaffinity-purified hen anti-brown antibodies (IgYp) mixed with TSAV reduced TSAV measured on TSV-coated wells. Both BSAV and TSAV prevented the clotting activity of both venoms. IgYp also prevented the clotting activity of TSV, suggesting true cross-reactivity. The cross-reactivity of TSAV and BSAV with BSV and TSV, respectively, was likely due to each being a mixture of anti-brown and anti-tiger antibodies, but there was partial cross-reactivity demonstrated by the effect of IgYp. Single-polyvalent antivenom for brown snake and tiger snake may be feasible in the future.

Prevalence of clinically actionable genotypes and medication exposure of older adults in the community.

This study analyzed clinically actionable pharmacogenotypes for clopidogrel, warfarin, statins, thiopurines, and tacrolimus using microarray data for 2121 participants (55-85 years) from the Australian Hunter Community Study (HCS). At least 74% of participants (95% confidence interval [CI]: 72%-76%) had strong level evidence for at least one medium- or high-risk actionable genotype that would trigger a change in standard therapy under current international recommendations. About 14% of these participants (95% CI: 12%-16%) were taking medication potentially affected by the genotype in question. Furthermore, ~2.6% of all participants with medication data (95% CI: 1.4%-3.8%) had a high-risk clinically actionable genotype for a medication to which they were exposed. This represents a considerable number of people at the population level. Although relationships between genotype and health outcomes remain contentious, pharmacogenotyping of multiple variants simultaneously may have considerable potential to improve medication safety and efficacy for older people in the community.

Enzyme immunoassays in brown snake (Pseudonaja spp.) envenoming: detecting venom, antivenom and venom-antivenom complexes.

Although a commercial snake venom detection kit (SVDK) is available to distinguish between the five major snake groups in Australia, there is no assay for quantifying venom or antivenom concentrations in envenomed patients. Serum samples were obtained from patients with brown snake (Pseudonaja spp.) envenoming before and after the administration of antivenom and patients with suspected brown snake bites but no evidence of envenoming. Enzyme immunoassays (EIAs) were developed for free venom, free antivenom and the venom-antivenom complex. Standard samples measured in duplicate had a coefficient of variation of less than 10%. The EIA for venom was able to detect brown snake venom down to concentrations of 3 ng/mL. A high baseline absorbance was measured in some patients that did not change with the addition of excess antivenom to the samples. In these patients, the baseline absorbance was subtracted from all measurements to calculate the true venom concentration. The EIA for brown snake antivenom had a limit of detection of 20 microg/mL, but 50 microg/mL was used as a cut-off based on assays in patients who had not received antivenom. The EIA for venom-antivenom complexes was unable to detect these at the low venom concentrations that occurred in patients. Quantification of venom and antivenom will help to determine the dose of antivenom required to bind venom and to establish appropriate end points for antivenom treatment.

Effect of tubing on loss of clonazepam administered by continuous subcutaneous infusion.

Previous studies have reported loss of clonazepam from solutions administered intravenously from plastic infusion bags and administration sets. In palliative care, clonazepam is sometimes administered through syringe drivers using polyvinyl chloride (PVC) infusion tubing. No data currently exist to show whether use of PVC tubing affects the amount of clonazepam actually received by the patient. This study compared the use of two different types of PVC tubing with a non-PVC tubing. Solutions containing clonazepam or clonazepam and morphine were prepared with either normal saline or water for injection as diluent. Concentrations of morphine and clonazepam were determined using high-performance liquid chromatography. Significant loss of clonazepam (up to 50%) was observed in all solutions infused through PVC tubing. Solutions infused through non-PVC tubing retained greater than 90% of the initial concentration of clonazepam. It is recommended that when administering clonazepam using a syringe driver, non-PVC tubing be used.

Use of high performance liquid chromatography to measure tetrodotoxin in serum and urine of poisoned patients.

Tetrodotoxin (TTX) poisoning is an infrequent but important problem in South-eastern Asia. Despite it being a considerable public health issue in some countries and its potential lethality there continues to be no readily available method for measuring TTX in urine or serum. Previously published methods have used immunoaffinity chromatography, or the conversion of TTX to its C9-base derivative for measurement by mass spectrometry. A simple and reproducible method was developed using solid phase extraction cartridges to clean up serum and urine samples from TTX-poisoned patients, and the subsequent analysis of the samples by high performance liquid chromatography with post-column derivatisation and fluorescence detection. Minimum quantifiable concentrations of TTX were 5 and 20 ng/ml for serum and urine, respectively. Precision and accuracy of the assay were 13 and 15%, respectively. The standard curves were linear in the range of 20-300 ng/ml for urine and 5-20 ng/ml for serum. TTX was quantified in six samples of urine and six samples of serum from seven patients who ingested common toadfish and had clinical effects consistent with TTX poisoning. TTX was detected in all urine samples but in only one serum sample. Using this method confirmation of TTX poisoning will be far simpler and readily available. A 24 h urine collection in the period immediately following poisoning is likely to be the most sensitive test for TTX poisoning. With appropriately collected and timed serum and urine specimens it will be possible to properly define the pharmacokinetics of TTX in humans.

The compatibility and stability of midazolam and dexamethasone in infusion solutions.

The delivery of subcutaneous medication by continuous infusion is common in palliative medicine. Many centers combine multiple medications, but the analytical confirmation of the compatibility and stability of these combinations has rarely been performed. This study examined the compatibility and stability of midazolam and dexamethasone using high performance liquid chromatography. Nine different solutions were prepared in polypropylene syringes by combining these two drugs with 0.9% sodium chloride. When these two drugs were combined in a syringe, there was significant loss of midazolam over 48 hours, with only 60-80% of the initial concentration remaining in syringes stored at 35-39 degrees C. This study demonstrates that cloudiness of a solution is not the only predictor of drug loss and that drug loss may occur even in solutions that remain clear at time of preparation. The clinical implications of these results are that dexamethasone and midazolam should not be combined in syringe driver solutions.

Targeting peripheral opioid receptors to promote analgesic and anti-inflammatory actions.

Mechanisms of endogenous pain control are significant. Increasing studies have clearly produced evidence for the clinical usefulness of opioids in peripheral analgesia. The immune system uses mechanisms of cell migration not only to fight pathogens but also to control pain and inflammation within injured tissue. It has been demonstrated that peripheral inflammatory pain can be effectively controlled by an interaction of immune cell-derived opioid peptides with opioid receptors on peripheral sensory nerve terminals. Experimental and clinical studies have clearly shown that activation of peripheral opioid receptors with exogenous opioid agonists and endogenous opioid peptides are able to produce significant analgesic and anti-inflammatory effects, without central opioid mediated side effects (e.g., respiratory depression, sedation, tolerance, dependence). This article will focus on the role of opioids in peripheral inflammatory conditions and the clinical implications of targeting peripheral opioid receptors.

Signal transduction pathways and tyrosine hydroxylase regulation in the adrenal medulla following glucoprivation: an in vivo analysis.

The regulation of tyrosine hydroxylase (TH, the rate limiting enzyme involved in catecholamine synthesis) is critical for the acute and sustained release of catecholamines from adrenal medullary chromaffin cells, however the mechanisms involved have only ever been investigated under in vitro/in situ conditions. Here we explored the effects on, TH phosphorylation and synthesis, and upstream signalling pathways, in the adrenal medulla evoked by the glucoprivic stimulus, 2-deoxy-d-glucose (2DG) administered intraperitoneally to conscious rats. Our results show that 2DG evoked expected increases in plasma adrenaline and glucose at 20 and 60min. We demonstrated that protein kinase A (PKA) and cyclin dependent kinases (CDK) were activated 20min following 2DG, whereas mitogen activated protein kinase (MAPK) was activated later and PKC was not significantly activated. We demonstrated that phosphorylation of Ser40TH peaked after 20min whereas phosphorylation of Ser31TH was still increasing at 60min. Serine 19 was not phosphorylated in this time frame. TH phosphorylation also occurred on newly synthesized protein 24h after 2DG. Thus 2DG increases secretion of adrenaline into the plasma and the consequent rise in glucose levels. In the adrenal medulla 2DG activates PKA, CDK and MAPK, and evokes phosphorylation of Ser40 and Ser31 in the short term and induces TH synthesis in the longer term all of which most likely contribute to increased capacity for the synthesis of adrenaline.

Expression of tyrosine hydroxylase increases the resistance of human neuroblastoma cells to oxidative insults.

In this study, we demonstrate that human neuroblastoma SH-SY5Y cells transfected with human tyrosine hydroxylase isoform 1 (SH + TH cells) were substantially more resistant to cell death induced by hydrogen peroxide and 6-hydroxydopamine when compared to wild-type SH-SY5Y cells (SH cells). SH + TH cells exhibit increased levels of dopamine (DA) compared to SH cells. Incubation with hydrogen peroxide or 6-hydroxydopamine (10-100microM) for 24 h caused a significant reduction in cell viability and increased apoptosis in both cell types. However, these effects were significantly reduced in the SH + TH cells when compared to the SH cells. The SH + TH cells showed an improved ability to detoxify peroxide, which correlated with an increase in glutathione peroxidase and glutathione reductase activities, while catalase activity was unchanged. Our data suggest that a preconditioning-like mechanism linked to higher DA levels increased the resistance of SH + TH cells against oxidative insults, which is at least in part related to an augmentation in the activity of glutathione-related antioxidant enzymes.

Cross-neutralisation of Australian brown snake, taipan and death adder venoms by monovalent antibodies.

An understanding of the cross-neutralisation of snake venoms by antibodies is important for snake antivenom development. We investigated the cross-neutralisation of brown snake (Pseudonaja textilis) venom, taipan (Oxyuranus scutellatus) venom and death adder (Acanthophis antarcticus) with commercial antivenoms and monovalent anti-snake IgG, using enzyme immunoassays, in vitro clotting and neurotoxicity assays. Each commercial antivenom bound all three venoms, and neutralised clotting activity of brown snake and taipan venoms and neurotoxicity of death adder venom. The 'in-house' monovalent anti-snake venom IgG raised against procoagulant brown snake and taipan venoms, did not neutralise the neurotoxic effects of death adder venom. However, they did cross-neutralise the procoagulant effects of both procoagulant venoms. This supports the idea of developing antivenoms against groups of snake toxins rather than individual snake venoms.