Determination of selamectin in dog plasma by high performance liquid chromatography with automated solid phase extraction and fluorescence detection

A method is described for the determination of selamectin in dog plasma, using High-Performance Liquid Chromatography (HPLC) with fluorescence detection (excitation and emission wavelengths fixed at 355 and 465 nm, respectively). The fluorescent derivative was obtained by condensation reaction with trifluoroacetic anhydride and N-methylimidazole. The method employs 1 mL plasma samples and gives linear calibration graphs ($r = 0.999$) over the concentration range studied ($0.5 - 50$ ng$\cdot$mL$^{-1}$). Automatic solid phase extraction using the benchmate procedure was used for sample preparation. This method permits the determination of selamectin at levels as low as 0.1 ng$\cdot$mL$^{-1}$ and its suitability was demonstrated by a pharmacokinetic study on a dog receiving the therapeutic dose (Spot-on administration).Dosage de la sélamectine dans le plasma de chien par chromatographie liquide haute performance avec une extraction en phase solide automatisée et une détection fluorimétrique. Cet article décrit une technique analytique qui permet de doser la sélamectine dans le plasma par chromatographie liquide haute performance, après formation d'un dérivé fluorescent ($\lambda_{{\rm max}}$ excitation = 355 nm et $\lambda_{{\rm max}}$ émission = 465 nm). Ce dernier composé est obtenu grâce à une réaction de condensation utilisant l'anhydride de l'acide trifluoroacétique et le N-méthylimidazole. La technique requiert 1 mL de plasma et la courbe de calibration obtenue est linéaire dans la gamme de concentrations étudiée ($0.5 - 50$ ng$\cdot$mL$^{-1}$). Une extraction en phase solide automatisée a été employée pour traiter les échantillons. Cette méthode présente une limite de détection de 0.1 ng$\cdot$mL$^{-1}$ et apparaît efficace pour conduire des études de pharmacocinétique dans différentes espèces. Un exemple de cinétique plasmatique chez le chien ayant reçu une dose thérapeutique de sélamectine (Spot-on) est décrite

ML modulation of the GABA-gated currents.

a<p>Concentration that evoked 50% of the maximal response for each ML.</p>b<p>Maximum potentiation relative to GABA alone.</p>c<p>n = 4 for calculation of concentration to reach E_max and E_max (%) for MOX, because for one egg, it was not possible to calculate the MOX E_max (%) from the fitted curve.</p>*<p>p<0.05 vs IVM;</p>***<p>p<0.001 <i>vs</i> IVM.</p

IVM and MOX concentrations in brain and brain-to-plasma ratio at increasing dose rates in Mdr1ab(−/−) and wild-type mice.

<p>IVM or MOX was administered to Mdr1ab(−/−) mice (6 per dose rate) or to wild-type mice (3 per dose rate) at increasing doses below the LD₅₀ to ensure a non-lethal effect of the administration. Drug concentrations were determined in brain and plasma after animals were sacrificed at 24 h post-treatment. Absolute brain accumulation was plotted against the plasma concentration to determine brain concentration at LD₅₀, brain-to-plasma concentration ratio calculated and R².</p>a<p>LD₅₀ determined graphically from <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001883#pntd-0001883-g001" target="_blank">Figure 1</a>.</p>b<p>LD₅₀ for IVM and MOX determined from the literature <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001883#pntd.0001883-Shoop1" target="_blank">[20]</a>, <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001883#pntd.0001883-WHO1" target="_blank">[21]</a>.</p>c<p>Brain concentration reached at LD₅₀, determined graphically from <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001883#pntd-0001883-g003" target="_blank">Figure 3A</a>.</p>d<p>Brain concentration reached at LD₅₀, determined graphically from <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001883#pntd-0001883-g003" target="_blank">Figure 3B</a>.</p>e<p>Brain-to-plasma concentration ratio calculated and R² obtained from the slope of the linear relationship between brain concentration and plasma concentration, which quantifies blood-brain transport.</p

Acute toxicity of IVM and MOX in Mdr1ab(−/−) mice.

<p>Acute toxicity was determined by observing survival during a 14-day period after subcutaneous administration of IVM (black square) or MOX (open square) to small groups (2–8 animals) of Mdr1ab(−/−) mice. Extrapolation from the graph yields an estimated LD₅₀ of 0.46 µmol/kg (0.40 mg/kg) and 2.3 µmol/kg (1.47 mg/kg) for IVM and MOX, respectively.</p

Absolute brain accumulation of MLs in Mdr1ab(−/−) and wild-type mice as a function of the administrated dose.

<p>IVM (filled squares) or MOX (empty squares) was administered to Mdr1ab(−/−) mice or to wild-type mice at increasing doses. Highest doses used for each ML were below the LD₅₀ to ensure a non-lethal effect of the administration. Mice in each group were sacrificed 24 h after treatment and drug concentrations were determined in brain and plasma. Absolute brain accumulation was plotted against the administrated dose in (<b>A</b>) Mdr1ab(−/−) or (<b>B</b>) wild-type mice. A positive and significant linear correlation was observed between brain uptake and the administered dose rate (R²>0.94 in all cases). All measurements are expressed as mean ± S.D. of six animals.</p

Comparison of chemical structures of ivermectin and moxidectin.

<p>Ivermectin is a mixture of B1a (substituent butyl on C25) and B1b (substituent isopropyl on C25) forms. The majority (more than 90%) of the drug is present as the B1a form.</p

Concentration-response curves of rat GABA(A) receptor expressed in <i>Xenopus</i> oocytes.

<p>(<b>A</b>) Average concentration-response curve for the reference agonist GABA alone. Data were normalized to the maximum GABA-evoked response and fitted to the Hill equation (EC₅₀ = 12.8±0.3 µM, Hill slope = 1.30±0.02. Data are given as mean ± S.E.M. from 3 independent oocytes batches (n = 4 oocytes for each batch). (<b>B</b>) Concentration-dependent potentiation of the GABA receptor, presented as the percentage of the GABA-evoked response at EC₁₀ (2 µM). To analyse the potentiation of the GABA-evoked current induced by IVM or MOX, GABA-responsive oocytes were exposed to 2 µM GABA, followed by washing and then 2 µM GABA in association with increasing concentrations of IVM (n = 8) or MOX (n = 5). Data were fitted to the Hill equation and are given as mean ± S.E.M.</p

Drug concentration in plasma and brain 2 and 24 h after SC administration of an equivalent molar dose rate of MLs in Mdr1ab(−/−) mice.

<p>Ivermectin (IVM) or moxidectin (MOX) was administered subcutaneously in Mdr1ab(−/−) mice (6 per drug) at similar molar dose rate (0.23 µmol/kg, corresponding to 0.20 mg/kg and 0.15 mg/kg for IVM and MOX, respectively). Mice were sacrificed at 2 or 24 h after treatment. Drug concentrations were determined in plasma and brain, and the brain/plasma concentration ratios were calculated.</p>*<p>p<0.05,</p>**<p>p<0.01,</p>***<p>p<0.001 <i>vs</i> IVM.</p

Neurological symptoms observed after IVM or MOX administration in Mdr1ab(−/−) mice.

<p>The Mdr1ab(−/−) mice (3 per dose rate) injected subcutaneously at dose rates of 0.11, 0.40 and 0.69 µmol/kg bw for IVM and 1.27, 1.64 and 2.56 µmol/kg bw for MOX were observed and the development of symptoms evoking neurologic signs (rapid breathing, balance problems, tremor, ataxia, sleepiness, lethargy) was recorded over a period of 2 weeks; every 60 min for the first 12 hours and thence minimally twice per day. Mice were euthanized when severe tremors or ataxia or profound lethargy was noted.</p>†<p>Mice were euthanized when severe tremor or ataxia was noted.</p>a<p>Dose rate averaging the LD₅₀ for IVM.</p>b<p>Dose rate averaging the LD₅₀ for MOX.</p>c<p>Ataxia: lack of voluntary <u>coordination of muscle movements</u>, as in walking.</p>d<p>Tremor: rhythmic, <u>muscle contraction</u> and relaxation involving <u>oscillations</u> or twitching.</p

A device to simulate contaminant transfer and surface and subsurface flow through intact soil monoliths

International audienceMany contaminants of agricultural origin are released into rural environments, particularly at the soil surface. Their fate has been extensively investigated in repacked soils, but only few studies have addressed their transport in structurally preserved natural soils. Much remains unknown about their fate and transfer within and between This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited