A case report of clonidine induced syncope: a review of central actions of an old cardiovascular drug

Evaluation of cilnidipine-loaded self-micro-emulsifying drug delivery system (SMEDDS) by quantification of comparative pharmacokinetic parameters using validated LC-ESI-MS/MS bioanalytical method and pharmacodynamic assessment

OBJECTIVE

Regardless of having desired therapeutic properties many of the recently approved drugs are removed from the developmental pipeline for their clinical use due to low solubility and permeability. Conventional dosage forms are found relatively unsuitable for achieving desired pharmacokinetic and pharmacodynamics profiles. Cilnidipine is 1,4 dihydropyridine derivative calcium channel blocker used for the treatment of hypertension.

METHOD

The aim and objective of this study was to develop a precise and significant method in LC-MS/MS for quantification of pharmacokinetic parameters of a cilnidipine-loaded self-micro-emulsifying drug delivery system in rat plasma and simultaneously assessed pharmacodynamic characters in comparison with the marketed cilnidipine tablet. Another potential aim of this study is to reduce the dose of the drug in order to counter the dose-dependent toxicities related to chronic use. In the present study, the parent and product ion of cilnidipine was m/z 491.3\237.1.

RESULT

The plasma was extracted by protein precipitation technique. The calibration standard concentrations were 1.875, 3.75, 7.50, 15.00, 30.00, 60.00ng/mL and LLOQ, low-quality control, middle-quality control and high-quality control were 1.87, 5.62, 22.50, 45.00ng/mL, respectively. The mobile phase composition was 0.1% formic acid in Milli Q water with 10mM Ammonium acetate as an aqueous solvent and 0.1% formic acid in methanol as an organic solvent. Following oral administration of optimized formulation Cmax (peak plasma concentration) was achieved 21.02±3.17ng/mL at 0.866±0.11h (Tmax), whereas in the case of marketed tablet Cmax (peak plasma concentration) was achieved 10.16±0.89ng/mL at 0.93±0.11h (Tmax).

DISCUSSION

The in-vivo characterizations of the optimized SMEDDS showed significantly better pharmacokinetic parameters in Wistar rats and showed almost 2.4 times enhanced relative bioavailability as compared to the marketed tablet of cilnidipine which was observed to be correlating to our findings with noninvasive blood pressure parameter of Wistar rats.

Vestibular neurons with direct projections to the solitary nucleus in the rat

Anterograde and retrograde tract tracing were combined with neurotransmitter and modulator immunolabeling to identify the chemical anatomy of vestibular nuclear neurons with direct projections to the solitary nucleus in rats. Direct, sparsely branched but highly varicose axonal projections from neurons in the caudal vestibular nuclei to the solitary nucleus were observed. The vestibular neurons giving rise to these projections were predominantly located in ipsilateral medial vestibular nucleus. The cell bodies were intensely glutamate immunofluorescent, and their axonal processes contained vesicular glutamate transporter 2, supporting the interpretation that the cells utilize glutamate for neurotransmission. The glutamate-immunofluorescent, retrogradely filled vestibular cells also contained the neuromodulator imidazoleacetic acid ribotide, which is an endogenous CNS ligand that participates in blood pressure regulation. The vestibulo-solitary neurons were encapsulated by axo-somatic GABAergic terminals, suggesting that they are under tight inhibitory control. The results establish a chemoanatomical basis for transient vestibular activation of the output pathways from the caudal and intermediate regions of the solitary nucleus. In this way, changes in static head position and movement of the head in space may directly influence heart rate, blood pressure, respiration, as well as gastrointestinal motility. This would provide one anatomical explanation for the synchronous heart rate and blood pressure responses observed after peripheral vestibular activation, as well as disorders ranging from neurogenic orthostatic hypotension, postural orthostatic tachycardia syndrome, and vasovagal syncope to the nausea and vomiting associated with motion sickness.NEW & NOTEWORTHY Vestibular neurons with direct projections to the solitary nucleus utilize glutamate for neurotransmission, modulated by imidazoleacetic acid ribotide. This is the first direct demonstration of the chemical neuroanatomy of the vestibulo-solitary pathway.