For acute nausea and vomiting associated with chemotherapy granisetron is used in prevention and treatment in similar doses.
In the Kenya, a dose equivalent to 3 mg of granisetron is diluted to a volume of 20 to 50 mL with a suitable infusion solution and given intravenously over 5 minutes before the start of chemotherapy; alternatively this dose may be given in 15 mL of infusion solution as a bolus over not less than 30 seconds. The dose may be repeated up to twice in 24 hours; doses should be given at least 10 minutes apart and a total daily dose of 9 mg should not be exceeded. The efficacy of granisetron may be enhanced by the use of dexamethasone. The recommended oral dose is 1 to 2 mg within one hour before therapy begins, then 2 mg daily as a single dose or in 2 divided doses.
In children, an intravenous infusion of 40 micrograms/kg, up to a maximum total dose of 3 mg, has been recommended, diluted in 10 to 30 mL of infusion fluid and given over 5 minutes. This dose may be repeated once within 24 hours, but at least 10 minutes after the original infusion. Alternatively, children may be given 20 micrograms/kg (up to 1 mg) twice daily by mouth for up to 5 days during therapy; the first dose should be given within 1 hour of the start of chemotherapy.
In the USA, lower intravenous doses of the equivalent of granisetron 10 micrograms/kg are recommended in both adults and children over 2 years of age, beginning within 30 minutes before chemotherapy. Doses by mouth are the same as those described for the UK above.
For the prevention of nausea and vomiting associated with radiotherapy in Kenya the recommended adult dosage is 2 mg daily by mouth taken within 1 hour of irradiation. The drug has also been given intravenously for the treatment and prevention of nausea and vomiting associated with radiotherapy, in similar doses to those recommended above for emetogenic chemotherapy. In the UK, the BNFC has recommended similar oral and intravenous doses to those given above (for chemotherapy-induced nausea and vomiting) in both the treatment and prevention of radiotherapy-induced nausea and vomiting in children.
For the prevention of postoperative nausea and vomiting in adults 1 mg is diluted to 5 mL and given by intravenous injection over 30 seconds. Injection should be completed before induction of anaesthesia. The same dose may be given up to twice daily for the treatment of established postoperative nausea and vomiting.
The manufacturer (Roche) has reported an increased incidence of hepatic neoplasms in rodents given very high doses of granisetron for prolonged periods, but the clinical relevance of these results is unknown in humans. Although mutagenicity and genotoxicity have not been seen in some tests, others have reported an increased incidence of polyploidy or unscheduled DNA synthesis in exposed cells.