From the FDA Drug Label
Gastrointestinal: The most commonly reported side effects at the initiation of therapy are nausea, vomiting, and indigestion. The FDA drug label does not answer the question.
From the Research
For patients taking sodium valproate, ondansetron (Zofran) is generally the preferred antiemetic due to its favorable safety profile and minimal drug interactions. The typical adult dosage is 4-8 mg orally or intravenously every 8 hours as needed for nausea and vomiting. For children, weight-based dosing applies. Ondansetron works by blocking serotonin 5-HT3 receptors in the chemoreceptor trigger zone and gastrointestinal tract, effectively reducing nausea signals to the brain. This mechanism is distinct from valproate's action, minimizing the risk of adverse interactions.
Some key points to consider when choosing an antiemetic for patients on sodium valproate include:
- Avoiding metoclopramide when possible, as it may lower the seizure threshold and potentially interfere with valproate's antiepileptic effects 1
- Using prochlorperazine cautiously due to its potential for causing extrapyramidal symptoms 1
- Monitoring for sedation when adding any antiemetic to valproate therapy, as central nervous system depression can be additive
- Considering alternative options such as granisetron or palonosetron if ondansetron is not tolerated
The most recent and highest quality study supporting the use of ondansetron as an antiemetic is from 2020, which highlights the effectiveness of serotonin antagonists, such as ondansetron, in treating nausea and vomiting 1. Another study from 2021 also supports the use of ondansetron as a second-line antiemetic, although it was a pilot trial that did not progress beyond the pilot phase due to slow recruitment 2.
Overall, the evidence suggests that ondansetron is a safe and effective antiemetic option for patients taking sodium valproate, with a low risk of adverse interactions and a favorable safety profile 3, 1, 4.