ABSTRACT
Acute attacks occur more commonly in women than in men and rarely before puberty. Acute attacks include abdominal pains (see Chapter 61), peripheral neuropathies, and changes in mental status that can be triggered by drugs, most notoriously the barbiturates. An unrecognized attack can be fatal (Table 87.2). In addition to drugs, fasting, infection, alcohol intake, psychological stress, menstruation, and pregnancy can precipitate attacks. Most porphyria -inducing drugs decrease haem levels by three possible mechanisms. First, they can stimulate cytochrome P450 synthesis, which leads to greater incorporation of haem. Second, they can destroy cytochromes, requiring more haem to be utilized in cytochrome production and thereby preventing haem from acting as the enzyme inhibitor. Last of all, they can alter the haem molecule such that it cannot negatively influence d-ALA synthase.
