IV Cyclizine 50mg TDS for Antiemetic Purposes
IV cyclizine 50mg three times daily is an appropriate antiemetic dose for patients with nausea and vomiting, particularly in palliative care settings where oral administration is not feasible.
Dosing and Administration
- The standard dose of cyclizine for antiemetic purposes is 50mg administered three times daily 1, 2
- This dosing regimen is consistent with clinical practice for antihistamine antiemetics
- Intravenous administration is appropriate when oral intake is compromised due to persistent vomiting 3
Efficacy and Evidence
- Cyclizine has demonstrated effectiveness as an antiemetic agent in clinical studies, with approximately 75% of patients experiencing benefit in palliative care settings 2
- A comparative study showed cyclizine 50mg was as effective as perphenazine 5mg in reducing emetic effects of opioids 1
- In a randomized trial examining post-operative nausea and vomiting, cyclizine showed different efficacy compared to other antiemetics like ondansetron and metoclopramide 4
Position in Antiemetic Therapy
While cyclizine is an appropriate antiemetic option, it's worth noting that current guidelines for chemotherapy-induced nausea and vomiting prioritize other agents:
- For highly emetogenic chemotherapy, guidelines recommend combinations of 5-HT3 antagonists (like ondansetron), dexamethasone, and NK-1 receptor antagonists 5
- For moderate to severe nausea and vomiting in cancer patients, first-line therapy typically includes ondansetron, dexamethasone, and olanzapine 3
- Cyclizine may be considered as an alternative or additional agent when first-line therapies are insufficient
Potential Side Effects and Monitoring
- Common side effects include:
- Constipation (13% of patients)
- Somnolence (9% of patients)
- Confusion (7% of patients) 2
- These side effects are generally tolerable, with only about one-third of patients experiencing adverse effects
- Monitor for potential abuse/misuse, as there have been reports of cyclizine misuse in cancer patients 6
Administration Considerations
- Around-the-clock administration (TDS) is preferred over PRN dosing to maintain consistent antiemetic effect 3
- Consider transitioning to oral cyclizine once vomiting is controlled and oral intake is possible 3
- For persistent nausea and vomiting despite cyclizine, consider adding or switching to a different antiemetic class (5-HT3 antagonists, NK-1 receptor antagonists, or dopamine antagonists) 5, 3
Clinical Pearls
- Evaluate for other causes of nausea and vomiting (constipation, bowel obstruction, metabolic disorders) if symptoms persist despite appropriate cyclizine dosing 5, 3
- Cyclizine may be particularly useful in opioid-induced nausea and vomiting 1
- Consider bioequivalence between different cyclizine formulations when transitioning between IV and oral routes 7
In summary, IV cyclizine 50mg TDS is an appropriate antiemetic dose with established efficacy and a generally favorable side effect profile, particularly when oral administration is not feasible.