Q. A 35-year-old woman comes to the emergency room with acute, diffuse abdominal pain, nausea, and confusion. She is a known case of acute intermittent porphyria. She had had the same attacks before and was treated with the administration of hemin; however, recently, the frequency of attacks has increased, and she had five attacks during the past year. She has no peripheral neuropathy, seizure, or bladder dysfunction. You start emergency treatment with hemin. What is the best plan for long-term control of her attacks?