Which drug is contraindicated in a patient with acute intermittent porphyria undergoing anesthesia?

Which drug is contraindicated in a patient with acute intermittent porphyria undergoing anesthesia?

• A. Pyridostigmine
• B. Isoflurane
• C. Propofol
• D. Thiopental

Answer: (D)

In acute intermittent porphyria, certain drugs trigger attacks by increasing the heme synthesis pathway. The key issue is whether a drug induces hepatic ALA synthase, the rate-limiting enzyme in porphyrin production. Thiopental is a barbiturate and a strong inducer of hepatic enzymes; it upregulates ALA synthase and boosts porphyrin precursor formation, which can precipitate a porphyric crisis during anesthesia. That makes it contraindicated in patients with acute intermittent porphyria. The other options are considered safer in porphyria because they do not significantly induce ALA synthase. Pyridostigmine, isoflurane, and propofol are not known to provoke porphyrin synthesis in a clinically meaningful way, so they are acceptable choices for anesthetic management in these patients.

In acute intermittent porphyria, certain drugs trigger attacks by increasing the heme synthesis pathway. The key issue is whether a drug induces hepatic ALA synthase, the rate-limiting enzyme in porphyrin production. Thiopental is a barbiturate and a strong inducer of hepatic enzymes; it upregulates ALA synthase and boosts porphyrin precursor formation, which can precipitate a porphyric crisis during anesthesia. That makes it contraindicated in patients with acute intermittent porphyria.

The other options are considered safer in porphyria because they do not significantly induce ALA synthase. Pyridostigmine, isoflurane, and propofol are not known to provoke porphyrin synthesis in a clinically meaningful way, so they are acceptable choices for anesthetic management in these patients.