“An urgent systemic review”
Dr. Nancy A. McNamara
Dr. McNamara’s research drilled down into the interaction of CBD and VPA. “Over the past several months we have made observations that several patients that had been started on CBD, also known as Epidiolex, had developed thrombocytopenia, some of which were symptomatic,” she said. Symptoms included hematuria, easy bruising, and gingival bleeding.
That prompted what Dr. McNamara called “an urgent systemic review” of all patients on CBD. Of 83 patients started on CBD for LGS from January to August 2019, 9 (11%) developed thrombocytopenia. “All of these patients were on concurrent VPA and no patients started on CBD without VPA developed thrombocytopenia,” she said. In all, 23 patients were taking CBD concurrently with VPA. Four of nine cases were symptomatic.
“The thrombocytopenia was reversible in all patients with reduction of medication and one patient recovered spontaneously without intervention,” Dr. McNamara noted.
“This was an important finding because this was not something that had come out of the clinical trials prior to FDA approval,” Dr. McNamara said. “This requires closer monitoring for patients who are started on CBD who are already on VPA.”
Of the 23 patients taking concurrent VPA, 10 had low platelet counts after starting CBD. In six patients, platelet counts dropped from normal before CBD therapy to low afterward.
The study used a McNemar test to determine if an observed adverse event occurred by chance or was related to starting a drug, which yielded a P value of .125, Dr. McNamara said. “While this did not achieve statistical significance, we suggest that prescribers closely monitor platelet levels after starting CBD, particularly when a patient is also on concurrent VPA,” she said.
Her group obtained a complete blood count at baseline and then at 1, 3, and 6 months after starting the patient on CBD, along with evaluation of alanine aminotransferase and aspartate aminotransferase. “We believe that this is helpful because most of the patients that develop low platelets did so within 3 months of starting cannabidiol,” Dr. McNamara said.
She acknowledged the limits of the single-center study. “Future research will need to be done with larger cohorts with standardized surveillance labs,” she said in an interview.
Dr. Patel disclosed financial relationships with GW Research and Greenwich Biosciences. Dr. McNamara has no relevant disclosures.