Among a series of methylated histamine derivatives, (R) alpha, (S) beta,-dimethylhistamine has been identified as a novel potent and selective H3-receptor agonist, even slightly more potent than (R) alpha-methylhistamine and displaying similar properties in vivo. Several studies suggesting that (R) alpha-methylhistamine might find various clinical applications, it was submitted to toxicological studies and initial clinical trials. The drug seems to display a very low animal toxicity, and, in humans, is well absorbed orally and metabolized via ring methylation before urinary excretion.