The serotonin syndrome scale: first results on validity.

As a modification of the diagnostic criteria of the serotonin syndrome proposed by Sternbach, we developed the Serotonin syndrome scale for the operationalized assessment of both the presence and the severity of the core symptoms of the serotonin syndrome. In a first study on the validity of this scale, the relationships between the serotonin syndrome score (SSS) and both the paroxetine plasma levels (n = 42) and the loudness dependence of the auditory evoked potentials (LDAEP; n = 24) were investigated in depressed patients treated with paroxetine. A strong LDAEP is supposed to indicate low central serotonergic neurotransmission, and vice versa. The SSS was positively related to paroxetine plasma levels and negatively to the LDAEP. Both results support the validity of the serotonin syndrome scale. Using a SSS > 6 as diagnostic criterion, mild serotonin syndromes were diagnosed in 5 of our 42 patients. The Serotonin syndrome scale may become a useful tool for clinicians and scientists dealing with the serotonin syndrome.