- Follow-up visits 3 and 6 months after the end of treatment either in person or by telephone Patients will have laboratory documentation of one of the acute porphyrias. Molecular documentation is also expected, although rarely a causative mutation cannot be detected. Upon entry into the study they will be given in a blinded fashion a single preventive dose of either Panhematin™ (4 mg/kg) or placebo. A recurrent attack within the next 1, 2, 3 and 4 weeks will represent treatment failures. Because at study entry most patients are expected to be on weekly prophylactic hemin treatment, and hemin is a short-acting drug, emphasis in the analysis will be on attacks occurring within 1 week after study treatment.