No. Emset and Ondem are both brand names for ondansetron, an anti-nausea medicine. Taking them simultaneously duplicates the same drug and can increase adverse effects without improving benefit.

Use only the one that was prescribed, at the prescribed dose and interval. Do not take an extra dose because one brand “didn’t work” without asking the prescriber or pharmacist.

Extra caution is needed if there is a history of long-QT syndrome, fainting/palpitations, heart rhythm disease, low potassium/magnesium, or use of other QT-prolonging drugs. Ondansetron can prolong the QT interval, and ECG monitoring may be appropriate in higher-risk people, according to the FDA prescribing information.

If both have already been taken and there is dizziness, fainting, a fast/irregular heartbeat, severe agitation, tremor, or fever, seek urgent medical advice.