Clonidine for anticipatory nausea and vomiting: a pilot study examining dose-toxicity relationships and potential for further study.

In preparation for studies of noradrenergic activity in anticipatory nausea and vomiting, we performed an open-dose study of clonidine to examine dose-toxicity relationships and indications of antiemetic activity. Nine patients, three each at 0.1, 0.2, and 0.4 mg/day, received clonidine twice a day for 5 days before chemotherapy. Unwanted effects, principally blood pressure reduction, dry mouth, and sedation, accumulated between 4 and 5 micrograms/kg/day. Four of eight evaluable patients had no anticipatory symptoms on clonidine. It is concluded that clonidine, at a dose of 4 micrograms/kg/day, might safely probe the role of noradrenergic activity in anticipatory nausea and vomiting.