A 35-year-old man has had recurrent attacks of abdominal pain and proximal motor neuropathy since puberty. The episodes are precipitated by infections and certain medications. During one of the attacks, the plasma porphobilinogen levels were increased. Which of the following medications is not considered safe in patients with this condition?

In patients with acute intermittent porphyria, oral phenothiazines may be used for abdominal or muscle pains, and narcotics may also be used, but barbiturates should be avoided. Sulfonamides are unsafe, but penicillin and its derivatives are safe. Other unsafe medications include alcohol, carbamazepine, valproic acid, and synthetic estrogens and progestagens. Most heterozygotes remain asymptomatic unless a precipitating factor such as a drug or weight loss is present. Poorly localized abdominal pain is the most common symptom