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For patients allergic to iodine contrast media (ICM), dexamethasone premedication prior to adrenal venous sampling (AVS) is a safe and more effective alternative to prednisone and other approaches when classifying primary aldosteronism (PA).

That's according to recent findings published in the .

Researchers at Centre Hospitalier of the University of Montreal in Canada identified 177 patients with confirmed PA who underwent bilateral simultaneous basal and post-adrenocorticotropic hormone (ACTH) bolus AVS. A total of 7 patients (4%) with previous allergic reactions to ICM were prepared with 3 doses of 7.5 mg of dexamethasone premedication rather than the usual 50 mg of prednisone, which can pose challenges when interpreting AVS results.

No breakthrough allergic reactions occurred in the 7 patients. Despite dexamethasone administration, cortisol response to ACTH was adequate.

Study co-author, Andre Lacroix, MD, is an endocrinologist-researcher with the center. He recently discussed the study and its findings with the Reading Room. The exchange has been edited for length and clarity.

This is something of a controversial topic. Why is that the case?

Lacroix: AVS is the optimal approach to adequately subtype PA into predominantly lateralized or bilateral disease is adrenal venous sampling. However, performing AVS in patients with ICM allergy is challenging.

Limited options are available for these patients. Alternative subtyping techniques include gadolinium-based contrast media for adrenal venography, carbon dioxide as a substitute for contrast dye, and radioiodine-labeled cholesterol analogue adrenal scintigraphy.

Each of these alternatives, however, poses significant clinical or technical challenges.

We've been doing AVS for more than 30 years, and had approached the problem differently.

How does your center approach the issue, and how did that approach lead to this study?

Lacroix: Generally, for people with ICM allergies, oral premedication with glucocorticoids (usually 3 doses of prednisone 50 mg) is administered at 13, 7, and 1 hours prior to the intervention. However, in the case of AVS, this method has long been abandoned, as prednisone can interfere with cortisol assays and suppress basal cortisol levels, rendering AVS interpretation difficult.

So instead of prednisone, we use dexamethasone. The advantage of dexamethasone over prednisone, is that it does not interfere with the measurement of cortisol and blood. At the same time, glucocorticoid pretreatment has been viewed by some as insufficiently safe to prevent ICM allergy.

We decided we would review the data that we had accumulated over the years on cases of AVS in patients with a history of ICM allergy.

How would you summarize what you discovered?

Lacroix: We went back and identified seven cases in which this procedure had been done under dexamethasone suppression. We demonstrated that in all cases, the AVS was adequate, that it allowed us to identify whether the PA was unilateral or bilateral, and that patients responded adequately to surgery when it was indicated.

Simply put, we demonstrated that dexamethasone is safe and allowed confirmation that the technical aspect was accomplished.

What are the clinical messages here that you think are important to emphasize?

Lacroix: This study demonstrated that a very simple substitution of prednisone by dexamethasone is efficient, and that none of the patients had any allergic reactions.

Severe contrast media allergy is not so frequent, but when it exists, you need to have a solution to be able to perform the exam, and to be able to offer the appropriate diagnosis and course of therapy for patients.

Our essential point was that you can substitute prednisone by dexamethasone in equivalent doses, and that it is efficient, safe, and allows adequate interpretation and performance of the examination.

Clinical implications

• Dexamethasone is safe and effective as a premedication alternative to prednisone for adrenal venous sampling in patients with primary aldosteronism with iodine contrast media allergies.
• Dexamethasone does not interfere with test interpretation like prednisone can.
• Alternative subtyping techniques, such as substituting iodine medium for gadolinium, can pose considerable technical or clinical problems.

Read the study here and expert commentary on the clinical implications here.