Investigating the KNDy hypothesis in humans by co-administration of kisspeptin, neurokinin B and naltrexone in men

Context: A subpopulation of hypothalamic neurons co-localise three neuropeptides namely kisspeptin, neurokinin B (NKB) and dynorphin collectively termed KNDy neurons. Animal studies suggest they interact to affect pulsatile GnRH release (KNDy hypothesis); kisspeptin stimulates, NKB modulates and dynorphin (an opioid) inhibits. Objective: To investigate the KNDy hypothesis in humans, we assessed for the first time the effects of co-administration of kisspeptin-54, NKB and an opioid receptor antagonist, naltrexone on LH pulsatility (surrogate marker for GnRH pulsatility) and gonadotropin release. Design, setting and participants: Ethically approved prospective, single-blinded placebo-controlled study. Healthy male volunteers (n=5/group) attended our research facility for 8 study visits. Intervention and main outcome measure: After 1h baseline blood sampling, participants received a different intervention at each visit: oral 50mg naltrexone (NAL), 8h intravenous infusions of vehicle, 2.56nmol/kg/h NKB (NKB), 0.1nmol/kg/h kissspeptin-54 (KP) alone and in combination. Frequent blood sampling to measure plasma gonadotropins and sex steroids was conducted and LH pulsatility was determined using blinded deconvolution analysis. Results: All kisspeptin and naltrexone containing groups potently increased LH and LH pulsatility (p<0.001 vs vehicle). NKB alone did not affect gonadotropins. NKB+KP had significantly lower increases in gonadotropins compared with kisspeptin alone (p<0.01). NAL+KP was the only group to significantly increase LH pulse amplitude (p<0.001 vs vehicle). Conclusions: Our results suggest significant interactions between the KNDy neuropeptides on LH pulsatility and gonadotropin release in humans. This has important implications for improving our understanding of GnRH pulse generation in humans

Pharmacokinetics of secnidazole in healthy volunteers after single oral dose

Introduction: Secnidazole is an anti infective agent which belongs to the 5-nitroimidazole class. Method: The objective of the trial was to characterize the pharmacokinetics of secnidazole after oral administration of a 2g dose, as microgranules formulation in healthy subjects. Blood samples were collected before, 1, 2, 3, 6, 9, 12, 24, 36, 48, 72, 96, 120, 168 and 240 h after dosing. Urines were collected in 24-h-fractions for the first five days and in 48 h-fraction for the last sample. The cumulative urinary excretion was captured for each subject from urine concentration (lg/L). Pharmacokinetic parameters were obtained by a non-compartmental approach (WinNonlin Pharsight). The assay was performed by ultra-performance liquid chromatography coupled with mass spectrometry detection (UPLC-MS/MS, Quattro Premier, Waters) after simple protein precipitation of 50 lL plasma sample. Chromatographic separation was done on a C18 Acquity column (50 mm · 2.1 mm, id 1.7 lm, Waters), in isocratic mode (80% water/0.1% formic acid and 20% acetonitrile). Ornidazole was used as internal standard. The detection was operated in positive mode and multiple reaction monitoring was used for quantification (186 &gt; 128 ion transition for secnidazole). The lower limit of quantification was 10 and 100 lg/L for plasma and urine samples respectively. Results: Sixteen subjects (8 female, 8 male) were included. Population characteristics such as: age ranged from 23 to 50 years (mean ± SD: 38 ± 9.2 years), weight ranged from 51 to 90 Kg (mean ± SD = 64.6 ± 10.1 Kg) and body mass index (BMI) ranged from 19.9 to 24.2 Kg/m 2 (mean ± SD = 21.9 ± 1.5 Kg/m 2 ;). Secnidazole exposure achieved a maximal concentration (Cmax) with a mean of 37.9 ± 8.5 mg/L (range 20–56 mg/L) and at a median time associated with the Cmax (Tmax) of 6 h (range 3–6 h). The area under the curve to the last measurable time (AUC0_t) and the total area under the curve (AUC0_¥) were 1281.9 ± 416.4 mg h/L and 1304.2 ± 444.1 mg h/L (mean ± SD) respectively. The Cl/F and V/F were 1.7 ± 0.5 L/h and 40.2 ± 9.2 L respectively and the elimination half-life (t1/2) was 17.5 ± 4.3 h (mean ± SD). The mean amount of secnidazole excreted in the 168-h urine collection was 310.47 mg (15.5% of the administered dose). For example, for the subject number 5, the observed parameters are: Cmax 37.3 mg/L, Tmax 3 h, AUC0_¥ 1029.5 mg h/L and t1/2 15.6 h. Conclusion: After a 2 g single oral dose, secnidazole presents a good absorption profile and relatively long elimination half life ensuring probable sufficient exposure with once a day administration

High-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) method for the simultaneous determination of diazepam, atropine and pralidoxime in human plasma

A high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) procedure for the simultaneous determination of diazepam from avizafone, atropine and pralidoxime in human plasma is described. Sample pretreatment consisted of protein precipitation from 100 μl of plasma using acetonitrile containing the internal standard (diazepam D5). Chromatographic separation was performed on a X-Terra® MS C8 column (100 mm × 2.1 mm, i.d. 3.5 μm), with a quick stepwise gradient using a formate buffer (pH 3, 2 mM) and acetonitrile at a flow rate of 0.2 ml/min. The triple quadrupole mass spectrometer was operated in positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges of 1–500 ng/ml for diazepam, 0.25–50 ng/ml for atropine and 5–1000 ng/ml for pralidoxime. The coefficients of variation were always &lt;15% for both intra-day and inter-day precision for each analyte. Mean accuracies were also within ±15%. This method has been successfully applied to a pharmacokinetic study of the three compounds after intramuscular injection of an avizafone–atropine–pralidoxime combination, in healthy subjects

A combined experimental and mathematical approach for molecular-based optimization of irinotecan circadian delivery

Circadian timing largely modifies efficacy and toxicity of many anticancer drugs. Recent findings suggest that optimal circadian delivery patterns depend on the patient genetic background. We present here a combined experimental and mathematical approach for the design of chronomodulated administration schedules tailored to the patient molecular profile. As a proof of concept we optimized exposure of Caco-2 colon cancer cells to irinotecan (CPT11), a cytotoxic drug approved for the treatment of colorectal cancer. CPT11 was bioactivated into SN38 and its efflux was mediated by ATP-Binding-Cassette (ABC) transporters in Caco-2 cells. After cell synchronization with a serum shock defining Circadian Time (CT) 0, circadian rhythms with a period of 26 h 50 (SD 63 min) were observed in the mRNA expression of clock genes REV-ERBα, PER2, BMAL1, the drug target topoisomerase 1 (TOP1), the activation enzyme carboxylesterase 2 (CES2), the deactivation enzyme UDP-glucuronosyltransferase 1, polypeptide A1 (UGT1A1), and efflux transporters ABCB1, ABCC1, ABCC2 and ABCG2. DNA-bound TOP1 protein amount in presence of CPT11, a marker of the drug PD, also displayed circadian variations. A mathematical model of CPT11 molecular pharmacokinetics-pharmacodynamics (PK-PD) was designed and fitted to experimental data. It predicted that CPT11 bioactivation was the main determinant of CPT11 PD circadian rhythm. We then adopted the therapeutics strategy of maximizing efficacy in non-synchronized cells, considered as cancer cells, under a constraint of maximum toxicity in synchronized cells, representing healthy ones. We considered exposure schemes in the form of an initial concentration of CPT11 given at a particular CT, over a duration ranging from 1 to 27 h. For any dose of CPT11, optimal exposure durations varied from 3h40 to 7h10. Optimal schemes started between CT2h10 and CT2h30, a time interval corresponding to 1h30 to 1h50 before the nadir of CPT11 bioactivation rhythm in healthy cells

Pharmacokinetics of secnidazole after single oral dose in healthy volunteers

National audienc

Organophosphorous neurotoxic antidotes : Pharmacokinetic analysis of avizafone hydrolysis and pralidoxime

Date du colloque&nbsp;: 04/2008</p

Pharmacokinetics of voriconazole and posaconazole administered in experimental models of disseminated scedosporiosis with cerebral involvement

International audienc