Not Medical Advice: If you mean white round G 4 pill, it has been identified as Ondansetron hydrochloride (orally disintegrating) 4 mg.
Ondansetron is used to prevent nausea and vomiting that is caused by cancer medicines (chemotherapy) or radiation therapy.
It is also used to prevent nausea and vomiting that may occur after surgery. Ondansetron works in the stomach to block the signals to the brain that cause nausea and vomiting. This medicine is available only with your doctor's prescription.
US Brand Names: