Phenoxybenzamine hydrochloride (NCI-c01661) is the hydrochloride salt form of phenoxybenzamine, a synthetic, dibenzamine alpha-adrenergic antagonist with antihypertensive and vasodilatory properties. Phenoxybenzamine non-selectively and irreversibly blocks the postsynaptic alpha-adrenergic receptor in smooth muscle, thereby preventing vasoconstriction, relieving vasospasms, and decreasing peripheral resistance. Reflex tachycardia may occur and may be enhanced by blockade of alpha-2 receptors which enhances norepinephrine release. Phenoxybenzamine is reasonably anticipated to be a human carcinogen.

The IC50 (100 nM) derived from the blockade of [3H]yohimbine binding by Phenoxybenzamine hydrochloride is significantly less than the IC50 (550 nM) for the corresponding reversal by Phenoxybenzamine hydrochloride of the effects of norepinephrine on cyclic AMP accumulation[1]. Phenoxybenzamine hydrochloride (50 nM) in conbination with Phenoxybenzamine hydrochloridetolamine (1000 nM) enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with pretreatment with Phenoxybenzamine hydrochloride (50 nM) alone in endothelium-intact aortae. Combined treatment with either dexmedetomidine (300 or 1000 nM) and Phenoxybenzamine hydrochloride (50 nM) or Phenoxybenzamine hydrochloridetolamine (1000 nM) and Phenoxybenzamine hydrochloride (50 nM) enhance Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with Phenoxybenzamine hydrochloride alone (50 nM). In addition, combined treatment with Phenoxybenzamine hydrochloridetolamine and Phenoxybenzamine hydrochloride enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with dexmedetomidine (1000 nM) and Phenoxybenzamine hydrochloride combined treatment. Combined treatment with high concentrations of dexmedetomidine (1000 nM) and Phenoxybenzamine hydrochloride enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with combined treatment with low concentrations of dexmedetomidine (300 nM) and Phenoxybenzamine hydrochloride[2].

Phenoxybenzamine hydrochloride (20 nM, s.c.) effectively suppresses the tumorigenesis of glioma cells in mice and the cell density in Phenoxybenzamine hydrochloride-U87 mg xenografts decreases significantly[3]. Phenoxybenzamine hydrochloride (1 mg/kg, i.v.) treated rats shows significant improvements in NSS and foot fault scoring[4].

Phenoxybenzamine hydrochloride is dissolved in DMSO. After cytometry, 1×3 cells are implanted in a 96-well plate in 100 μL DMEM supplemented with 10 % FBS. Ten microliter (10 % of the total volume) WST-1 (Water Soluble Tetrazolium) is added to cells and incubated at 37°C for 30 min before colorimetric assay with 450 nm excitation and 630 nm emission at 24 h intervals up to 96 h. The mean fluorescence value is counted, and the cell number is determined using the standard curve.