Clinical pharmacology and therapeutics
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Clin. Pharmacol. Ther. · Jul 1988
Comparative StudyThe role of alpha-adrenoceptor blockade in the antihypertensive effects of fenoldopam in humans.
Fenoldopam, a dopamine-1 receptor agonist, has been reported to exhibit alpha-adrenoceptor-blocking actions in intact and isolated animal preparations. To determine whether alpha-adrenoceptor blockade contributes to its antihypertensive properties in humans, the effects of fenoldopam on the pressor responses to norepinephrine and angiotensin II were compared in eight normal volunteers. ⋯ Dose ratios for an increase in mean blood pressure of 10 mm Hg were 3.3 +/- 0.9 for norepinephrine and 3.2 +/- 0.6 for angiotensin II (p not significant). Consequently, fenoldopam is not a selective alpha-adrenoceptor antagonist at therapeutic concentrations in humans.
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Clin. Pharmacol. Ther. · Jul 1988
Comparative StudyCumulative dose-response with infusion: a technique to determine neuromuscular blocking potency of atracurium and vecuronium.
The ability of cumulative dose-response techniques to obtain accurate data is most likely limited by redistribution and elimination of the drug during the study period. Therefore the usefulness of these techniques would be improved by replacing the amount of drug lost. This hypothesis was assessed for the intermediate-duration neuromuscular blockers vecuronium and atracurium, and calculations were made based on a pharmacokinetic model with an effect compartment. ⋯ For atracurium the ED90 was 0.175 +/- 0.009 (SD), 0.206 +/- 0.019 (CD), and 0.179 +/- 0.015 mg/kg (CDI). Calculated values corresponded well with measured values. The calculations predicted that the agreement between single- and cumulative-dose techniques would be improved if (1) the dose increment was increased, (2) the elimination half-life was increased above 20 minutes, or (3) an infusion was added.(ABSTRACT TRUNCATED AT 250 WORDS)