I have been prescribing mirtazapine (Remeron) and paroxetine (Paxil) to control violence, aggressivity, and psychotic behaviors in young patients with mental retardation. These agents control violence within a few days (not one to two weeks), while neuroleptics fail. Can you explain the effect and the speed of action?
—Truc H. Dao, MD, Rowland Heights, Calif.

It is often difficult to assess the clinical condition driving aggressive or disorganized behavior in patients with mental retardation. The psychiatric differential includes mood and anxiety disorders, schizophrenia, and disorders of impulse control. Medical conditions, such as chronic pain syndromes, may also lead to behavioral disinhibition. In such patients, the putative mechanism of action for selective serotonin reuptake inhibitor (SSRI) and serotonin norepinephrine reuptake inhibitor (SNRI) medications, alone or in combination, might include rapid relief of anxiety (due to enhancement of serotonin), sedation due to antimuscarinic and antihistaminic effects, or drug-drug interaction leading to elevated mirtazapine levels (since SSRIs and SNRIs are CYP2D6 substrates).

The ineffectiveness of antipsychotic medication indicates that the underlying disorder is not a primary psychotic disorder.
—David Brody, MD, physician-in-charge of Psychiatric Outpatient Services, and Michael Serby, MD, associate chairman Department of Psychiatry, Beth Israel Medical Center, New York City (106-2)

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