REVIEW Fenoldopam is a rapid-acting vasodilator. It is an agonist for D1-like dopamine receptors and binds with moderate affinity to alpha-2-adrenoceptors. It has no significant affinity for D2-like receptors, alpha-1 and beta--adrenoceptors, 5HT1 and 5HT2 receptors, or muscarinic receptors. Fenoldopam is a racemic mixture with the R-isomer responsible for the biological activity. The R-isomer has approximately 250-fold higher affinity for D1-like receptors than does the S-isomer. In non-clinical studies, fenoldopam had no agonist effect on presynaptic D2-like dopamine receptors, or alpha- or beta- -adrenoceptors, nor did it affect angiotensin-converting enzyme activity. Fenoldopam may increase norepinephrine plasma concentration.