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Introduction
Cyclizine is a histamine H1 receptor antagonist, prescribed as an antiemetic, that can be administered off-label via continuous subcutaneous infusion (CSCI).
Current guidance suggests a conversion ratio of oral to subcutaneous cyclizine of 2:1, and recommended starting dose of 75 mg over 24 hours via CSCI.1 A study established an approximate bioavailability of 50% following administration of a single dose of cyclizine in six healthy volunteers. However, the pharmacokinetics of cyclizine have not been clearly defined within the palliative population or via the subcutaneous route.2
We conducted a retrospective survey to determine current prescribing practice. We aimed to establish whether a conversion ratio of oral to subcutaneous cyclizine of 2:1, (thus starting dose of 75 mg) was in use, and to review subsequent dose titration.
Methods
Patients prescribed cyclizine via CSCI between November 2022 and June 2022 were identified. Data were obtained from electronic records and included: indication, starting dose, subsequent dose titration, and documented evidence of symptom benefit and adverse effects.
Standards were based on current guidelines for prescription of subcutaneous cyclizine, which recommend ratio of oral to subcutaneous cyclizine of 2:1, and starting dose of 75 mg, (maximum 200 mg) over 24 …
Footnotes
Contributors FV conducted the survey, analysed the data and wrote the manuscript. MP reviewed the data and contributed to the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.