PRL and serotonin syndrome: Supportive evidence comes from two other aspects of this trial: firstly, a patient took a monoamine oxidase inhibitor prior to treatment with DMXAA at 1650 mg m−2 and developed clinical features of the serotonin syndrome; and secondly an acute increase in plasma prolactin levels seen in many patients treated with DMXAA at ⩾2000 mg m−2 (unpublished results).