Dextrorphan (tartrate) (Synonyms: d-3-hydroxy-N-Methylmorphinan tartrate, NIH 4591)

Dextrorphan (tartrate) is a phencyclidine-like metabolite of dextromethorphan, kwoun as an antitussive in cough medicines ^[1]. Dextrorphan (tartrate) is a noncompetitive N-methyl-d-aspartate (NMDA) antagonist that is neuroprotective in experimental models of focal brain ischemia ^[2]. Dextrorphan (tartrate) concentrations producing IC50 of K+-stimulated 45Ca 2+ uptake into brain synaptosomes was 200±27µM ^[3].

Dextrorphan (tartrate) inhibit excitatory amino acid (EAA) evoked neuronal responses 3, apparently by acting at a site on the NMDA-preferring EAA receptor or its associated Ca 2+ channel. Dextromethorphan and dextrorphan (tartrate) protect neurons from EAA-induced cytotoxicity ^[3].

In dextrorphan-treated patients, transient and reversible adverse effects, including nystagmus, nausea, vomiting, somnolence, hallucinations, and agitation, commonly occurred. Loading-dose escalation was stopped because of rapid-onset, reversible, symptomatic hypotension in 7 of 21 patients treated with doses of 200 to 260 mg/h. Maximum plasma levels of 750 to 1000 ng/mL were obtained in 9 patients ^[2].

References:
[1]. Shin, E.J., Lee, P.H., Kim, H.J., et al. Neuropsychotoxicity of abused drugs: Potential of dextromethorphan and novel neuroprotective analogs of dextromethorphan with improved safety profiles in terms of abuse and neuroprotective effects. Journal of Pharmacological Sciences 106(1), 22-27 (2008).
[2]. Albers GW, Atkinson RP, Kelley RE, Rosenbaum DM; Dextrorphan Study Group. Safety, tolerability, and pharmacokinetics of the N-methyl-d-aspartate antagonist dextrorphan in patients with acute stroke.Stroke. 1995; 26:254-258.
[3]. Carpenter CL, Marks SS, Watson DL, Greenberg DA. Dextromethorphan and dextrorphan as calcium channel antagonists. Brain Res.1988; 439:372-375.