Idazoxan hydrochloride

Development of a radioimmunoassay for idazoxan hydrochloride.[Pubmed:2100607]

J Pharm Biomed Anal. 1990;8(8-12):685-9.

To facilitate the measurement of idazoxan in clinical trials an immunoassay capable of detecting low ng ml-1 concentrations was required. A stable derivative was prepared which, after linking to keyhole limpet hemocyanin (KLH), was subsequently immunized into sheep. Early assay development was carried out with both fluorescent (1-FITC) and iodinated (I-125) labels. The assay methodology was the same in both cases, using magnetizable solid-phase particles to which the antibody was linked. The sensitivity of the assay was such that a large sample volume was required, which in turn, led to problems of increased protein interference. The use of pepsin to digest the protein was used effectively after several blocking agents were unsuccessfully used. The limit of detection was in the region of 3 ng ml-1. Cross-reactivity studies showed that the antibody was specific for idazoxan. Intra- and inter-assay precision was 7 and 12%, respectively. Correlation with the analytical GC-MSD method was in the order of 0.90.

Evaluation of xylazine hydrochloride as the sole immobilizing agent in moose and caribou--and its subsequent reversal with idazoxan.[Pubmed:2563404]

J Wildl Dis. 1989 Jan;25(1):95-8.

Xylazine hydrochloride was used as the sole immobilizing agent in moose and caribou. The animals were free-ranging and immobilization was accomplished from a helicopter using powered darts. Following a period of immobilization during which radiotelemetry collars were fitted, the animals were revived using idazoxan (RX 781094) or its methoxy analogue RX 821002. Xylazine was administered at dose rates of approximately 3.0 mg/kg and 5.0 mg/kg to the moose and caribou, respectively. Moose received 430 +/- 27 mg of xylazine and a mean dose of 10 mg idazoxan (RX 781094). Caribou received 485 +/- 30 mg xylazine and a mean dose of 4 mg idazoxan (RX 821002). This technique gave adequate immobilization with rapid recovery of consciousness in both species.

Antineoplastic activity of idazoxan hydrochloride.[Pubmed:19308411]

Cancer Chemother Pharmacol. 2009 Nov;64(6):1157-63.

PURPOSE: Idazoxan hydrochloride (IDA) is a 241 molecular weight imidazoline and adrenoreceptor ligand. It binds to mitochondrial membranes and promotes apoptosis of pancreatic beta cells. Since IDA has not been tested against tumor cells, the purpose of our study was to determine if IDA has antineoplastic activity. METHODS: We used the conversion of a soluble tetrazolium salt to an insoluble formazan precipitate and differential staining cytotoxicity assays to determine if IDA was cytotoxic to cell lines of murine lung cancer and human prostate cancer, as well as to a variety of fresh human tumor samples. We used flow cytometry to analyze cell death and calreticulin expression. RESULTS: IDA is cytotoxic to both cell lines and against aliquots of specimens of breast, gastric, lung, ovarian and prostate cancers as well as non-Hodgkin's lymphoma. It produces apoptotic cell death and promotes calreticulin expression, suggesting that IDA might be immunomodulatory in vivo. CONCLUSION: We anticipate that IDA will be clinically useful in cancer treatment.

Field immobilization of bighorn sheep with xylazine hydrochloride and antagonism with idazoxan.[Pubmed:1979085]

J Wildl Dis. 1990 Oct;26(4):522-7.

Xylazine hydrochloride was used to immobilize 124 Rocky Mountain bighorn sheep (Ovis canadensis canadensis) between 1983 and 1988. Doses of xylazine for free-ranging lambs ranged from 70 to 130 mg with amounts increasing with lamb age. Average doses for 11 free-ranging adult males and 21 adult females darted from the ground were (means +/- SE) 363 +/- 16 and 251 +/- 7 mg, respectively. Adult females captured in "Stevenson's " box traps (n = 7) could be immobilized with significantly (P less than 0.001) less xylazine (93 +/- 9 mg) than free-ranging females but had similar induction times. Long recovery times associated with xylazine immobilization were eliminated with the intravenous administration of idazoxan (RX 781094) at an approximate dosage of 0.1 mg/kg. Eighteen sheep given idazoxan appeared fully recovered within 3 min of injection (means +/- SE = 1.2 +/- 0.2 min). Four mortalities (three lambs, one yearling male) (3% of total) occurred before idazoxan was available for trial.

'Seeing through a glass darkly': casting light on imidazoline 'I' sites.[Pubmed:9786027]

Trends Pharmacol Sci. 1998 Sep;19(9):381-90.

Although imidazoline sites have been the subject of research for several years, there is still controversy about their structure, diversity and physiology. The I1 site is thought to exist principally as a binding site and is widely purported to play a role in controlling systemic blood pressure, although this is still unclear. The majority of I2 sites are widely accepted as being allosteric sites on monoamine oxidase; however, even with selective ligands, their exact function remains to be determined. A putative I3 site modulates insulin secretion and could represent the first functional site to be pharmacologically defined with selective agonists and antagonists. The structure and relevance of the proposed endogenous ligand 'clonidine-displacing substance' remains elusive. A potential candidate for this substance is agmatine; however, although it is capable of displacing bound clonidine from imidazoline sites, it lacks the functionality ascribed to the clonidine-displacing substance. In this review, Richard M. Eglen and colleagues assess our knowledge of imidazoline sites in the light of recent data.

Evidence for two different imidazoline sites on pancreatic B cells and vascular bed in rat.[Pubmed:7774667]

Eur J Pharmacol. 1995 Feb 24;275(1):91-8.

The relative potencies of imidazoline compounds to induce insulin secretion and vascular resistance were compared in the isolated perfused rat pancreas. On insulin secretion, only the two imidazolines, antazoline and efaroxan, induced a concentration-dependent response, antazoline being 10 times more potent than efaroxan. In contrast, idazoxan, a blocker of imidazoline I1 sites, at concentrations up to 30 microM, antagonized the insulin response to 10 microM efaroxan (IC50 approximately equal to 14 +/- 2 microM) without affecting that to 3 microM tolbutamide. On pancreatic vessels, not only antazoline and efaroxan but also idazoxan induced a concentration-dependent vasoconstriction; the rank order of agonist potency was antazoline > efaroxan > idazoxan. In addition, cimetidine, an imidazole known to bind imidazoline I1 sites, ineffective per se, partially reversed the insulin stimulatory effect of efaroxan without affecting its vasoconstrictor effect. This study demonstrates that the insulin secretory and vasoconstrictor actions of imidazolines involve different imidazoline sites in rat pancreas. The results provide evidence for an I1 type mediating insulin secretion on B cells and an I2 type mediating vasoconstriction in vessels.

Idazoxan: a novel pharmacological tool for the study of alpha 2-adrenoceptors.[Pubmed:2875218]

J Pharmacol. 1986 Apr-Jun;17(2):113-8.

The pharmacological properties of idazoxan, 2-[2-(1,4-benzodioxanyl)]-2-imidazoline, were first described four years ago; since then, this compound has been revealed to be one of the most selective alpha 2-adrenoceptor blocking agent presently available. At peripheral sites, idazoxan antagonized the effects of alpha 2 agonists such as azepexole, B-HT 920, M 7, UK 14,304, alpha-methylnoradrenaline, clonidine but was ineffective against alpha 1 agonists such as cirazoline and phenylephrine. At presynaptic sites idazoxan increased the tachycardia due to the stimulation of the cardioaccelerator nerve of the dog and antagonized the inhibitory effects of alpha 2 agonists in dogs and rats. As compared to the classical alpha 2-adrenoceptor blocking agents, idazoxan was more selective and as potent as yohimbine, rauwolscine, RS 21361, Wy 26703. At central sites, idazoxan has been found to antagonize the sympathoinhibitory effects of alpha 2 agonists. Therefore, idazoxan is a potent and probably the most selective alpha 2-adrenoceptor blocking agent presently available and is now frequently used for the investigation of peripheral and central alpha 2-adrenoceptors.

Idazoxan hydrochloride (RX 781094 hydrochloride) is an α2-adrenoceptor antagonist and is also a imidazoline receptors (IRs) antagonist competitively antagonized the centrally induced hypotensive effect of imidazoline-like drugs (IMs). Idazoxan hydrochloride also improves motor symptoms in Parkinson’s disease, L-DOPA-induced dyskinesias, and experimental Parkinsonism.

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