- Patients taking medications known to have significant drug-drug interactions with the prescribed drug and study drugs, Dronabinol and Ondansetron, will be reviewed in Micromedex. Micromedex is a medication database used by Central Arkansas Veterans Healthcare System (CAVHS). If the drug could have a drug-drug interaction with either dronabinol or ondansetron the patients will NOT be entered into the study. If a drug is confirmed via Micromedex not to have a drug-drug interaction, the patient will be eligible for study participation.