Chlorpromazine bioavailability from a topical gel formulation in volunteers.

Background: Symptom management medications are often compounded into topical gel formulations providing an alternative route of administration for hospice and palliative care patients. Though commonly used, transdermal absorption and bioavailability studies of these gel products are lacking. Chlorpromazine was studied because it is FDA approved for treatment of nausea and vomiting and is used off-label for treatment of agitation and delirium.

Objective: The objective of this study is to determine the transdermal absorption of chlorpromazine PLO gel in healthy adults.

Methods: Twenty-five milligrams of chlorpromazine in PLO gel was applied to 10 subjects' wrists and 100 mg was applied to 1 subject's wrist. Blood draws were completed preapplication and 1, 2, and 4 hours postapplication. This single-center unblinded study recruited healthy adults between 18 and 70 years of age. Participants were not pregnant, did not have an allergy to any component of the study medication, and were not taking a phenothiazine medication.

Results: Chlorpromazine was undetected in any of the 11 subjects' blood samples.

Limitations: There is an assumption of equivalent medication absorption in healthy patients and palliative care or hospice patients.

Conclusion: Rapid relief of symptoms at end of life is essential. Chlorpromazine in PLO gel may not be an effective treatment option since blood levels were undetectable at 1, 2, and 4 hours after topical application.