Effect of UK-52,046, an alpha 1-adrenoceptor antagonist, on baroreflex function in man

Dose-dependent alpha 1-adrenoceptor antagonist activity of the anti-arrhythmic drug, abanoquil (UK-52,046), without reduction in blood pressure in man

1. The dose-dependency of the alpha 1-adrenoceptor antagonist activity of the anti-arrhythmic abanoquil (UK-52,046) was investigated in 10 healthy male subjects who received serially increasing infusions of phenylephrine before and 2, 4, 8, 12, 24 and 48 h after single oral doses of abanoquil 0.25, 0.5 and 1 mg and placebo in a double-blind randomised manner. 2. The doses of phenylephrine required to increase systolic BP by 20 mm Hg (PS20) were calculated using a quadratic fit to the individual dose-response curves. 3. Abanoquil 0.25, 0.5 and 1 mg increased the PS20 in a dose-dependent manner with effects which were maximal at 2 to 8 h and lasted for 24 to 48 h (P less than 0.05). Maximal dose ratios were: abanoquil 0.25 mg 2.0 +/- 0.9, 0.5 mg 2.4 +/- 1.3, 1 mg 3.4 +/- 1.1. 4. No change occurred in supine BP but a small increase (P less than 0.01) occurred in supine HR 8 h post-dosing (64 +/- 9, 58 +/- 6 beats min-1 for abanoquil 1 mg and placebo respectively). 5. Therefore abanoquil 0.25, 0.5 and 1 mg showed dose-dependent alpha 1-adrenoceptor antagonist activity with no effect on supine BP.

Studies with abanoquil (UK-52,046) a novel quinoline alpha 1-adrenoceptor antagonist: II. Duration of action, pharmacokinetics and concentration-effect relationships in normotensive subjects

1. This study further examines the quinoline-derivative abanoquil with particular respect to the duration of its alpha 1-adrenoceptor antagonist activity and its concentration-effect relationship following a single intravenous bolus dose of 0.5 micrograms kg-1 in young, normotensive males. 2. alpha 1-adrenoceptor antagonism (as assessed by phenylephrine pressor responses) was detectable for up to 12 h post dosing: at 12 h there was a significant 1.5-fold rightward shift (95% CI: 2.2 to 1.1) of the pressor dose-response curve for diastolic blood pressure. 3. Despite evidence of substantial alpha 1-adrenoceptor antagonism abanoquil had no significant effect on blood pressure, supine and erect, but there were small and statistically significant increments in heart rate. 4. The degree of alpha 1-adrenoceptor antagonism was related to whole blood concentrations abanoquil: the PD-ratios of phenylephrine pressor responses performed at 1, 6, and 12 h post dosing were significantly correlated with log drug concentrations (r = 0.57 for systolic (P less than 0.05) and r = 0.78 for diastolic blood pressure (P less than 0.005). 5. In conclusion, abanoquil produced significant alpha 1-adrenoceptor antagonism which was related to circulating drug concentrations. The absence of other significant cardiovascular effects suggests that abanoquil warrants further clinical study as an antiarrhythmic agent.