Dolasetron (dolasetron mesilate) is a pseudopelletierine-derived 5-HT3 antagonist which has recently become available for clinical use. It is rapidly converted in vivo to its active major metabolite, hydrodolasetron, which appears to be largely responsible for its pharmacological activity. In clinical trials, single intravenous or oral doses of dolasetron were effective in preventing acute chemotherapy-induced nausea and vomiting (CINV). Intravenous doses of 1.8 mg/kg achieved complete suppression of vomiting in approximately 50% of patients receiving highly emetogenic cisplatin-containing chemotherapy and in approximately 60 to 80% of patients receiving moderately emetogenic chemotherapy. In the latter setting, oral doses of 200mg achieved similar response rates. In comparative studies, intravenous dolasetron 1.8 mg/kg was as effective as intravenous granisetron 3mg or ondansetron 32mg after highly emetogenic chemotherapy, and oral dolasetron 200mg was equivalent to multiple oral doses of ondansetron (3 or 4 doses of 8mg) after moderately emetogenic chemotherapy. Dolasetron 1.8 mg/kg was superior to metoclopramide in preventing emesis induced by high nose cisplatin or by moderately emetogenic chemotherapy in high risk subgroups. Dolasetron has also shown efficacy in preventing radiotherapy-induced nausea and vomiting (RINV) in preliminary studies. Single intravenous or oral dolasetron doses ranging from 12.5 to 100mg and 25 to 200mg, respectively, were significantly more effective than placebo in preventing postoperative nausea and vomiting (PONV) in female surgical patients. A 50mg intravenous dose was as effective in preventing PONV as ondansetron 4mg in a mixed-gender group. Intravenously administered dolasetron was also effective in treating established PONV although complete suppression of vomiting was achieved in <40% of patients. Dolasetron has a tolerability profile characteristic of this class of compounds, with headache, dizziness and diarrhoea being the most commonly occurring adverse events in clinical trials. Diarrhoea is not thought to be related to dolasetron administration, being experienced mostly by patients receiving chemotherapy, Dolasetron and other 5-HT3 receptor antagonists have been associated with minor changes in ECG intervals, but these generally do not appear to be clinically important. Thus, available evidence suggests that dolasetron will provide an alternative to other 5-HT3 receptor antagonists for the management of CINV and PONV. Further studies are required to determine whether it offers any advantages over other agents in these settings and to determine the optimum dosage for preventing RINV.
