Determination of the purity of valine by isocratic liquid chromatography coupled with charged aerosol detection (CAD).

A liquid chromatography coupled with charged aerosol detection (LC-CAD) procedure; capable of separating and quantifying the most common impurities of valine at levels as low as 0.05 per cent (m/m), has been developed. The procedure is simple (isocratic), rapid, linear, sensitive and repeatable. It employs a widely available and inexpensive stationary phase (C18).

Current management and recommendations for access to antiviral therapy of herpes labialis.

Herpes labialis is a common skin infective condition, worldwide, which is primarily caused by HSV-1. Recurrent episodes of herpes labialis, also known as cold sores, can be frequent, painful, long-lasting and disfiguring for infected patients. At present, there are two types of antivirals for the treatment of herpes labialis, topical and oral, which are available over the counter or as prescription-only. The aim of antiviral therapy is to block viral replication to enable shortening the duration of symptoms and to accelerate healing of the lesions associated with herpes labialis. This review examines the evidence for the effectiveness of current topical and oral antivirals in the management of recurrent episodes of herpes labialis. In most countries, oral antivirals for herpes labialis are available as prescription-only. However, in early 2010, the oral antiviral famciclovir was reclassified from prescription-only medicine to pharmacist-controlled status in New Zealand. The benefits and risks associated with moving an antiviral therapy for herpes labialis from prescription-only to pharmacist-controlled status are reviewed here, and the implications for patients, general physicians and pharmacists are considered.

Metabolome analysis of gram-positive bacteria such as Staphylococcus aureus by GC-MS and LC-MS.

The field of metabolomics has become increasingly important in the context of functional genomics. Together with other "omics" data, the investigation of the metabolome is an essential part of systems biology. Beside the analysis of human and animal biofluids, the investigation of the microbial physiology by methods of metabolomics has gained increased attention. For example, the analysis of metabolic processes during growth or virulence factor expression is crucially important to understand pathogenesis of bacteria. Common bioanalytical techniques for metabolome analysis include liquid and gas chromatographic methods coupled to mass spectrometry (LC-MS and GC-MS) and spectroscopic approaches such as NMR. In order to achieve metabolome data representing the physiological status of a microorganism, well-verified protocols for sampling and analysis are necessary. This chapter presents a detailed protocol for metabolome analysis of the Gram-positive bacterium Staphylococcus aureus. A detailed manual for cell sampling and metabolite extraction is given, followed by the description of the analytical procedures GC-MS and LC-MS. The advantages and limitations of each experimental setup are discussed. Here, a guideline specified for S. aureus metabolomics and information for important protocol steps are presented, to avoid common pitfalls in microbial metabolome analysis.

Characterization of two new potential impurities of Valsartan obtained under photodegradation stress condition.

A photostability study of Valsartan (VAL) is reported. Exposure of the drug to UV-vis radiation (λ > 320 nm) yielded two previously unknown compounds, which were detected by HPLC. Preparative amounts of the new potential degradation products (DP-1 and DP-2) were obtained by submitting VAL bulk drug to extensive photodegradation. The impurities were isolated by preparative normal phase column chromatography. Analytical information from the infrared, nuclear magnetic resonance and mass spectral data of the degradation products revealed their structures as N-[2'-(1H-tetrazol-5-yl)-biphenyl-4-ylmethyl]-N-isobutylpentanamide (DP-1) and N-(diazirino[1,3-f]phenanthridin-4-ylmethyl)-N-isobutylpentanamide (DP-2). DP-1 arose from decarboxylation of VAL, while DP-2 results from further loss of nitrogen from the tetrazole motif of DP-1, with concomitant cyclization to yield a tetracyclic diazacyclopropene derivative.

Do placebo based validation standards mimic real batch products behaviour? Case studies.

Analytical methods validation is a mandatory step to evaluate the ability of developed methods to provide accurate results for their routine application. Validation usually involves validation standards or quality control samples that are prepared in placebo or reconstituted matrix made of a mixture of all the ingredients composing the drug product except the active substance or the analyte under investigation. However, one of the main concerns that can be made with this approach is that it may lack an important source of variability that come from the manufacturing process. The question that remains at the end of the validation step is about the transferability of the quantitative performance from validation standards to real authentic drug product samples. In this work, this topic is investigated through three case studies. Three analytical methods were validated using the commonly spiked placebo validation standards at several concentration levels as well as using samples coming from authentic batch samples (tablets and syrups). The results showed that, depending on the type of response function used as calibration curve, there were various degrees of differences in the results accuracy obtained with the two types of samples. Nonetheless the use of spiked placebo validation standards was showed to mimic relatively well the quantitative behaviour of the analytical methods with authentic batch samples. Adding these authentic batch samples into the validation design may help the analyst to select and confirm the most fit for purpose calibration curve and thus increase the accuracy and reliability of the results generated by the method in routine application.

Biovalidation of an SPE-HPLC-UV-fluorescence method for the determination of valsartan and its metabolite valeryl-4-hydroxy-valsartan in human plasma.

A simple and fast method for the simultaneous determination of the antihypertensive drug Valsartan and its metabolite in human plasma has been validated. The proposed method deals with SPE, followed by an HPLC separation coupled with fluorimetric and photometric detection. The optimization of the SPE-HPLC method was achieved by an experimental design. The separation was performed on an RP C18 Atlantis 100 mmx3.9 mm column. The mobile phase consisted of a mixture of ACN 0.025% TFA and phosphate buffer (5 mM, pH = 2.5) 0.025% TFA and was delivered in gradient mode at a flow rate of 1.30 mL/min. The eluent was monitored with a fluorescence detector at 234 and 378 nm excitation and emission wavelengths, respectively, and at 254 nm using a photometric detector. The full analytical validation was performed according to the Food and Drug Administration (FDA) 'guidance for industry: bioanalytical method validation' and the recoveries obtained for Valsartan and its metabolite ranged from 94.6 to 108.8%. The validated method was successfully applied to 12 plasma samples obtained from patients under antihypertensive treatment with Valsartan.

Valacyclovir prophylaxis for the prevention of Herpes simplex virus reactivation in recipients of progenitor cells transplantation.

HSV can cause oral lesions that exacerbate chemotherapy-related mucositis. Intravenous acyclovir is effective in preventing HSV reactivations, but expensive. Valacyclovir has good bioavailability and has not been studied for prophylaxis of HSV among PCT patients. We compared the efficacy and costs of valacyclovir in preventing HSV reactivation among HSV seropositive autologous progenitor cell transplantation (APCT) patients with historical controls in whom intravenous acyclovir or no HSV prophylaxis were used. Valacyclovir group: From October 1997 to April 1999 108 adult patients received valacyclovir 500 mg twice daily from day -3 of APCT until neutropenia recovery or day +30. Valacyclovir was switched to intravenous acyclovir in cases of oral intolerance (17 patients) or suspected HSV reactivation (five patients). Intravenous acyclovir group: From January 1996 to October 1997 43 patients received 5 mg/kg twice-daily intravenous acyclovir from day -3 until recovery from neutropenia. No prophylaxis group: 38 patients from January 1996 to October 1997 did not receive HSV prophylaxis. HSV reactivations were seen in 2.7%, 2% and 45% of patients in the valacyclovir, intravenous acyclovir, and no prophylaxis groups, respectively. Valacyclovir was well tolerated and was the least expensive strategy. Oral valacyclovir was as effective as intravenous acyclovir for the prophylaxis of HSV reactivation in APCT patients.

Canadian valsartan study in patients with mild-to-moderate hypertension.

OBJECTIVE: This study was designed mainly to establish the rates of response to valsartan 80mg once daily (qd) and to valsartan 160mg qd given to non-responders to 80mg qd, as well as to determine the safety of valsartan and the blood pressure control achieved using valsartan over a period of 24 h or more, using ambulatory blood pressure monitoring (ABPM) devices. METHODS: This was a single-blind, single-arm, multicenter study involving 256 out-patients with mild-to-moderate essential hypertension. After previous antihypertensive treatments had been 'washed out', the patients were entered into a 2-week placebo run-in period to confirm the diagnosis of mild-to-moderate hypertension. Patients who, at the end of the placebo run-in period, had a mean sitting diastolic blood pressure of between 95 and 115mmHg inclusive received valsartan 80mg qd for 4 weeks. Non-responders (those not demonstrating a diastolic blood pressure of less than 90mmHg or a decrease in diastolic blood pressure of 10mmHg or more compared with baseline) received valsartan 160mg qd for another 4 weeks. In selected centers, patients who agreed also had their blood pressure monitored for 24 h, provided their blood pressure was shown to be controlled. Of these patients, half skipped one dose of valsartan and were monitored for an additional 24h period. RESULTS: The rate of response to valsartan 80mg was 45.4%, and of those not responding to this dose, 36.3% responded to valsartan 160mg. The response rate to one or other dose was 63.2%. The ambulatory blood pressure data support a consistent reduction of blood pressure with valsartan over a 24h period and for up to 32 h after dosing in those who missed a dose. The overall incidence of adverse experiences per person-year, treatment related or otherwise, was 6.3 and 10.6 for the valsartan and placebo study periods respectively. CONCLUSION: Antihypertensive treatment with valsartan for 8 weeks produced a significant decrease in diastolic blood pressure in hypertensive patients. In addition, the drug may be safely administered, and the results of 24 h/48 h ambulatory monitoring demonstrate that valsartan is a true once-a-day antihypertensive.

Increasing valine, isoleucine, and total branched-chain amino acids for lactating sows.

One hundred eighty-five (n = 24 to 27/group; average parity 1.3) sows (PIC, Line C-15) were used to evaluate effects of the interrelationship between isoleucine and valine on sow and litter performance. Diets were formulated to .90% total lysine with all amino acids other than isoleucine and valine at least 110% of their suggested requirement estimate relative to lysine using ratios derived from the National and Agricultural Research Councils. The control diet was formulated to .50% isoleucine and .72% valine. L-Valine and L-isoleucine replaced cornstarch to provide .72 or 1.07% dietary valine, and .50, .85, or 1.20% isoleucine. A seventh diet contained .50% isoleucine and 1.42% valine. Mean litter size after cross-fostering was 11.1 pigs, and average lactation length was 20.3 d. No valine x isoleucine interactions were observed (P > .10) for most response criteria. Number of pigs weaned (mean = 10.9), sow feed intake (mean = 6.13 kg), and lysine intake (mean = 55 g/d) were not affected by dietary isoleucine or valine. Litter weight and weight gain at weaning increased as dietary valine (P < .07), isoleucine (linear, P < .07), and total branched-chain amino acids (linear, P < .02) increased. Twelve sows per treatment (84 total) were milked manually on either d 17 or 18 of lactation. Increasing dietary valine increased milk DM and fat (linear, P < .01). Milk DM, CP, and fat increased (linear, P < .002) as dietary isoleucine increased. The casein fraction of milk protein increased (linear, P < .01) and whey and nonprotein N fractions decreased (linear, P < .06, P < .01, respectively) as dietary isoleucine increased. Based on these results, valine and isoleucine increased litter weights. The independent increases in litter weaning weights from adding valine and isoleucine suggest separate modes of action in lactating sows.

Valine requirement of the finishing pig.

Pigs weighing approximately 70 kg were used in two experiments to determine the valine requirement during the finishing period. In the first experiment, 10 gilts were allotted in two 5 x 5 Latin square designs to five semipurified diets that ranged in valine concentration from .35 to .55%. Urinary urea excretion was measured during each of the 3-d periods of the Latin square. Urea N excretion in relation to N intake and to creatinine N excretion was minimized (quadratic effect, P < .10) at valine concentrations of .45 to .50%. In Exp. 2, 36 barrows and 36 gilts were fed one of six diets containing .35 to .60% valine. The highest weight gains (not significant) and feed efficiencies (quadratic effect, P < .05) were achieved by the pigs that consumed .45% valine. Plasma urea concentration at the end of the experiment was lowest (quadratic effect, P < .05) in pigs that consumed .50% valine. Estimates of the valine requirement based on breakpoint and quadratic equation analyses ranged from .40 to .50% total valine (.33 to .43% ileal digestible valine). Pigs in Exp. 2 consumed approximately 2.5 kg/d (8,850 kcal/d of ME). Thus, the estimate of the valine requirement is approximately 11 g/d. These estimates of the valine requirements of finishing pigs are slightly higher than the National Research Council requirements when expressed as a percentage of the diet but are similar when expressed on a grams per day basis.