Introduction: Graves’ disease is typically managed with antithyroid drugs (ATDs) and beta-blockers like propranolol. While allergic reactions to ATDs are common, beta-blockers are rarely identified as allergens. Case: A 42-year-old female with Graves’ disease was started on carbimazole 5 mg daily and propranolol 40 mg daily. She developed mild itchiness, which was tolerable. One month later, liver enzyme derangement led to the discontinuation of carbimazole. Propylthiouracil (PTU) 300 mg daily was initiated while continuing propranolol, but caused generalized urticaria, necessitating its cessation. Prednisolone was started, but her thyroid function worsened. Alternative therapies were proposed but declined by the patient. Upon resolution of urticaria, PTU was reintroduced at 50 mg daily without adverse effects, and propranolol was discontinued. Her cutaneous symptoms did not recur, implicating propranolol as the allergen. Conclusion In hyperthyroidism, increased hepatic clearance reduces plasma propranolol levels, minimizing the risk of adverse effects. However, as thyroid function normalizes, propranolol clearance slows, leading to drug accumulation and increased susceptibility to side effects. Clinicians should consider all medications as potential allergens and understand how thyroid states affect drug metabolism to optimize treatment.
Graves Disease ; Allergens