Quantification of cyclic AMP and cyclic GMP levels in Krebs-Henseleit solution by LC-MS/MS: Application in washed platelet aggregation samples.

Cyclic Nucleotides are important in regulating platelet function. Increases in 3'5'-cyclic adenosine monophosphate (cAMP) and 3'5'-cyclic guanosine monophosphate (cGMP) inhibit platelet aggregation and are pharmacological targets for antiplatelet therapy. Here we report an improved method for determining cAMP and cGMP concentrations and, for the first time, in washed platelet supernatants by combining high-performance liquid chromatography and tandem mass spectrometry (LC-MS/MS). Characteristic peaks of the substrates, cGMP or cAMP and their internal standards were identified in negative-ion electrospray ionisation using multiple reaction monitoring. Compared with previously reported methods, the method presented here shows high precision with the lowest lower limit of quantification (LLoQ) to date (10 pg/mL). The effect of a novel catecholamine, 6-nitrodopamine, on cyclic nucleotide levels was quantified. Our results showed that this new method was fast, sensitive, and highly reproducible.

Quantification of 6-nitrodopamine in Krebs-Henseleit's solution by LC-MS/MS for the assessment of its basal release from Chelonoidis carbonaria aortae in vitro.

In this study, the development and validation of a method for quantification of 6-nitrodopamine in Krebs-Henseleit's solution by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with positive ion electrospray ionization is described. Aortic rings taken from tortoise were either denuded or left with endothelium intact (15 mm, N = 6) and were incubated for 30 min in 5 mL Krebs-Henseleit's solution in an organ bath. Solid phase extraction (SPE) was performed for aliquots of 1 mL of the supernatant. The separation of 6-nitrodopamine was obtained on a 150 mm × 3 mm Shim-pack GIST-HP C18 column, using 75% of mobile phase A consisted of deionized water with 0.1% formic acid (v/v) and 25% of mobile phase B consisted of acetonitrile/deionized water (50/50, v/v) + 0.1% formic acid at a flow rate of 350 µL/min in an isocratic mode. The method was linear over the concentration range of 0.1-20 ng/mL. The method was sensitive, precise and accurate for the assessment of the basal release of 6-nitrodopamine from Chelonoidis carbonaria aortae in vitro. The mean ± SEM concentrations of 6-nitrodopamine released from endothelium-intact and endothelium-denuded aortae were 0.44 ± 0.06 ng/mL and 0.18 ± 0.05 ng/mL, respectively. These results indicate that tortoise's aortae display a basal endothelium-derived 6-nitrodopamine release.

Quantification of estradiol cypionate in plasma by liquid chromatography coupled with tandem mass spectrometry: Application in a pharmacokinetic study in healthy female volunteers.

The combination of medroxyprogesterone acetate 25 mg + estradiol cypionate 5 mg is a highly effective, monthly injectable contraceptive. For the first time, this study presents the development and validation of a sensitive method for estradiol cypionate analysis in human plasma by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Aliquots (500 µL) of plasma were extracted with ethyl ether (100%) and derivatized with dansyl chloride. Its separation was performed on a Jones Chromatography Genesis C8 column and the quantification was performed with a mass spectrometer equipped with an electrospray interface operating in negative ion mode. The run time was 6 min and the calibration curve was linear over the range of 0.005-0.15 ng/mL. The method was applied to evaluate the pharmacokinetics of estradiol cypionate in plasma collected up to 1008 h (42 days) after a single intramuscular administration of 25 mg/mL medroxyprogesterone acetate +5 mg/mL estradiol cypionate to healthy female volunteers (n = 12). The estradiol cypionate maximum plasma concentration (Cmax) was 0.14 ± 0.08 ng/mL reached at 16.83 ± 21.07 h and the area under the plasma concentration versus time curve (AUC0-last) was 14.07 ± 6.32 ng.h/mL. Elimination half-life (t½), apparent volume of distribution (Vd/F), apparent clearance (CL/F) and mean residence time (MRT) were 89.65 ± 76.04 h, 28038 ± 9636 L, 49.02 ± 10.62 L/h and 576.05 ± 238.32 h, respectively, showing that the estradiol cypionate release from the administration site was prolonged and there was no drug accumulation.

Randomized, double-blind, phase III clinical study of a novel nanotechnological topical anesthetic formulation containing lidocaine 25 mg/g and prilocaine 25 mg/g (nanorap) in skin phototypes I-III patients with ablative fractional CO2 laser treatment indication in the forehead.

BACKGROUND AND OBJECTIVES: Nanotechnology may increase the speed of penetration into the skin. This study evaluated the efficacy, safety, and pharmacokinetics of a novel topical anesthetic nanocapsule formulation (2 g) containing 2.5% lidocaine and 2.5% prilocaine (nanorap-test formulation) compared to placebo (control formulation) in skin types I-III patients of both sexes submitted to the ablative fractional CO2 laser treatment. METHODS: The patients (n = 120) included in this double-blind, single-center, randomized trial, received topical application of 2 g of the test formulation (50 mg lidocaine + 50 mg prilocaine) and placebo on the forehead region. Efficacy was assessed as pain sensation in four quadrants of each side of the forehead using a visual analogue scale immediately (0 min) and at 30, 60, and 90 minutes after laser application compared to placebo. The safety and tolerability of the test product were evaluated based on the occurrence of systemic adverse events as well as the occurrence of immediate and late skin reactions. Pharmacokinetic evaluation was performed in plasma of eight patients using a validated LC-MS/MS method for drugs quantification. RESULTS: Nanorap induced a clinically significant reduction in the pain assessment at all evaluated times (57.2%, 41.6%, 38.6%, and 37.3% at 0, 30, 60, and 90 minutes after drug application, respectively. Mean values of Cmax were 14.20 and 5.36 ng/ml and tmax were 3.5 and 1.8 hour for lidocaine and prilocaine, respectively. No systemic adverse events were observed. CONCLUSION: The nanorap formulation demonstrated a clinically and statistically significant efficacy providing analgesia after the ablative fractional CO2 laser therapy in the investigated patients, when compared to placebo. The product also presented good safety and tolerability. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Impact of Bariatric Surgery on the Pharmacokinetics Parameters of Amoxicillin.

BACKGROUND: Bariatric surgery leads to several anatomo-physiological modifications that may affect pharmacokinetic parameters and consequently alter the therapeutic effect of drugs, such as antibiotics. The pharmacokinetics of oral amoxicillin after Roux-en-Y gastric bypass (RYGB) surgery is unknown. OBJECTIVES: The objective of this study was to evaluate the impact of bariatric surgery on the pharmacokinetics of amoxicillin. METHODS: This study was performed as a randomized, open-label, single-dose clinical trial, with two periods of treatment, in which obese subjects (n = 8) received an amoxicillin 500 mg capsule orally before and 2 months after the RYGB surgery. The amoxicillin plasma concentration was determined by liquid chromatography coupled to mass spectrometry (LC-MS/MS). RESULTS: After the surgery, the mean weight loss was 17.03 ± 5.51 kg, and mean body mass index (BMI) decreased from 46.21 ± 2.82 to 38.82 ± 3.32 kg/m2. The mean amoxicillin area under the plasma concentration versus time curve from time zero to the time of the last quantifiable concentration (AUC0-tlast) increased significantly (3.5-fold); the maximum plasma concentration (Cmax) increased 2.8-fold after the bariatric surgery. No correlation was found between amoxicillin absorption, BMI, and weight loss percentage. CONCLUSION: The alterations observed in the amoxicillin pharmacokinetics suggest that obese subjects included in this trial had a substantially increase in amoxicillin systemic exposure after RYGB surgery. However, despite this increase, its exposure was lower than the values reported for non-obese volunteers. TRIAL REGISTRATION: Identifiers: NCT03588273.