Do dopamine partial agonists have partial efficacy as antipsychotics?

CNS Spectr 13:4 April 2008 279 NEW TREND IN PSYCHOPHARMACOLOGY Dopamine (D)2 partial agonists (DPAs) activate D2 receptors in a manner that is less than the full agonist dopamine yet more than full antagonists (eg, most known antipsychotics). Various DPAs span the spectrum between full agonist at one end and antagonists at the other, with the antipsychotic aripiprazole close to the antagonist end of this spectrum, and with the antiparkinsonian/restless legs syndrome agents pramipaxole and ropinirole close to the full agonist end of this spectrum (Figure). Numerous DPAs have been tested as antipsychotics, but most have proven to have limited efficacy as antipsychotics or even to be psychotomimetic. Recent experience with a number of DPAs now suggests that although these agents may have less efficacy as antipsychotics than D2 antagonists, their novel pharmacologic actions may have important clinical utility in mood disorders and as augmenting agents to reduce the side effects of D2 antagonists (Table).