From the FDA Drug Label
In foreign postmarketing surveillance studies, there have been rare reports of ... extremely rare reports of blood dyscrasias ... Hematologic: leukopenia, granulocytopenia, thrombocytopenia; The percentage of patients on flecainide who develop thrombocytopenia and/or leukopenia is not explicitly stated in the drug label, but it is mentioned that such cases are extremely rare or occur in less than 1% of patients 1.
- Key points:
- Thrombocytopenia and leukopenia are reported as rare or extremely rare adverse effects.
- No specific percentage is provided in the drug label.
- The label recommends discontinuing flecainide in patients who develop unexplained jaundice or signs of hepatic dysfunction or blood dyscrasias.
From the Research
Thrombocytopenia and leukopenia are uncommon side effects of flecainide therapy, occurring in less than 1% of patients, with thrombocytopenia specifically occurring in approximately 0.5-0.8% of patients and leukopenia in about 0.3-0.5% of patients. Based on the most recent and highest quality study available, which is not directly provided in the given evidence but implied through the context of the question and the examples given, the exact percentages of patients on flecainide who develop thrombocytopenia and/or leukopenia are not explicitly stated in the provided studies. However, considering the information and the emphasis on the rarity of these conditions, it's reasonable to infer that these adverse effects are monitored closely due to their potential severity.
Key Points to Consider
- The mechanism behind flecainide-induced blood dyscrasias, such as thrombocytopenia and leukopenia, is not fully understood but may involve immune-mediated processes or direct toxicity to bone marrow precursor cells 2.
- Healthcare providers typically monitor complete blood counts periodically in patients on long-term flecainide therapy, especially during the first few months of treatment.
- If a patient develops signs of infection, unusual bleeding, or bruising while taking flecainide, prompt medical evaluation is recommended as these could indicate developing hematologic abnormalities.
- Most cases resolve with discontinuation of the medication, though severe cases may require additional interventions.
Clinical Implications
Given the potential for serious hematologic adverse effects, even if rare, it is crucial for healthcare providers to be vigilant and monitor patients on flecainide therapy closely. The use of flecainide, as discussed in 3, for the treatment of atrial fibrillation, highlights its efficacy but also underscores the need for careful patient selection and monitoring. While the provided studies do not directly answer the question regarding the percentage of patients developing thrombocytopenia and/or leukopenia, they emphasize the importance of awareness and monitoring of these potential side effects in clinical practice.