Sulfasalazine-Associated Thrombocytopenia

Incidence and Risk Factors

• The Toronto Consensus Guidelines list thrombocytopenia among the most common adverse events, occurring in up to 15% of patients taking 5-ASA compounds, which includes sulfasalazine, in patients with ulcerative colitis 1
• The American Gastroenterological Association notes that rare but serious hematologic toxicity is possible with sulfasalazine, requiring laboratory monitoring of complete blood counts in patients with inflammatory bowel disease 2

Management and Monitoring

• The American College of Rheumatology recommends holding or decreasing sulfasalazine immediately when clinically relevant thrombocytopenia occurs alongside other laboratory abnormalities in patients with rheumatoid arthritis 3
• Complete blood counts should be performed frequently during sulfasalazine therapy, with a monitoring protocol of CBC every 2 weeks for the first 3 months, monthly CBC for the second 3 months, and every 3 months thereafter 4
• The American College of Rheumatology recommends rechecking CBC within 1-2 weeks to confirm improvement after discontinuing sulfasalazine due to thrombocytopenia 3
• Considering alternative 5-ASA medications such as mesalamine or balsalazide if sulfasalazine must be discontinued for inflammatory bowel disease 5