Objectives To describe the contemporary real-world use of cyclizine for nausea or vomiting, and the associated benefits and harms.

Methods This was a prospective, consecutive case series of routine clinical use of cyclizine for nausea or vomiting in palliative care conducted across 19 sites in Australia, Aotearoa/New Zealand and the UK. Clinical outcomes were graded using the National Cancer Institute Common Terminology Criteria for Adverse Events at baseline and 72 hours after initiation of cyclizine. Ad hoc safety reporting continued for 2 weeks.

Results Data were collected from 101 patients between May 2018 and December 2020. Cyclizine was mostly used in combination with another antiemetic. Overall, 79 patients benefited and 32 experienced harm (56 had benefit without harm; 9 had harm without benefit). The most common harms were constipation (13%), somnolence (9%) and confusion (7%), adding to the already high rates of these symptoms at baseline. For the four patients with serious harms (grade ≥3), these were exacerbations of existing symptoms. Nine patients stopped cyclizine at 72 hours and a further 20 patients within 2 weeks. The most common reasons for stopping were lack of benefit and symptom resolution; none stopped because of harms.

Conclusions When used as described in a palliative care setting, cyclizine benefits about three-quarters of patients, with about one-third experiencing tolerable harms.