From the Guidelines
Yes, you can give ondansetron to a patient who is still vomiting despite being on metoclopramide. These medications work through different mechanisms - metoclopramide is primarily a dopamine antagonist that also increases gastric emptying, while ondansetron is a serotonin (5-HT3) receptor antagonist. Using both medications together is a common approach for managing persistent nausea and vomiting, as supported by the AGA clinical practice update on management of medically refractory gastroparesis 1. For adults, a typical ondansetron dose is 4-8 mg orally or intravenously every 8-12 hours as needed, as outlined in the treatment options for refractory gastroparesis symptoms 1. When adding ondansetron, monitor the patient for potential side effects including headache, constipation, and QT interval prolongation on ECG, especially in patients with cardiac conditions or electrolyte abnormalities. Some key points to consider when using ondansetron in this context include:
- The dose and frequency of ondansetron administration, which can be adjusted based on patient response and tolerance
- The potential for drug interactions, particularly with other medications that may affect the QT interval
- The importance of ongoing monitoring and evaluation to assess the effectiveness of the treatment and identify any potential side effects or complications
- The need for further evaluation if vomiting persists despite both medications, as this could indicate a more serious underlying condition requiring different management. It's also worth noting that other treatment options, such as domperidone, granisetron, and aprepitant, may also be considered for patients with refractory gastroparesis symptoms, as discussed in the AGA clinical practice update 1. However, the use of these medications should be guided by the individual patient's needs and circumstances, and should be based on the best available evidence and clinical judgment.
From the Research
Patient on Metoclopramide but Still Vomiting
- Can ondansetron be given to a patient on metoclopramide who is still vomiting?
Efficacy of Ondansetron and Metoclopramide
- A study published in 2014 2 compared the efficacy of ondansetron and metoclopramide with placebo for adults with undifferentiated emergency department nausea and vomiting, and found that reductions in nausea severity were similar for both drugs.
- Another study published in 2018 3 compared the effectiveness of bromopride, metoclopramide, and ondansetron for treating vomiting in children, and found that ondansetron was superior to both other agents in preventing vomiting six hours and 24 hours after treatment.
- A study published in 2018 4 compared the efficacy of metoclopramide and ondansetron in improving nausea and vomiting in patients with renal colic, and found that ondansetron was more effective than metoclopramide in preventing and improving vomiting.
Combination Therapy
- A pilot study published in 2021 5 investigated the use of ondansetron and metoclopramide as second-line antiemetics in women with nausea and vomiting in pregnancy, but was unable to provide evidence to support clinician decisions due to slow recruitment.