Do inhaled corticosteroids (ICS) interfere with dexamethasone (Decadron) suppression testing?

From the Guidelines

Inhaled corticosteroids can interfere with dexamethasone suppression testing, and it is recommended to discontinue their use for at least 1-2 weeks before testing when possible, due to their potential to cause false-positive results by suppressing the hypothalamic-pituitary-adrenal axis. The degree of interference depends on the specific medication, dosage, and duration of use, as demonstrated by studies such as the DICE study 1, which established the dose of six different ICS products that rendered similar degrees of hypothalamic-pituitary-adrenal axis suppression. Some key points to consider when evaluating the impact of inhaled corticosteroids on dexamethasone suppression testing include:

• The specific type of inhaled corticosteroid used, with some medications such as fluticasone and budesonide having a higher potential for systemic absorption and subsequent interference with the test
• The dosage and duration of use, with higher doses and longer durations of use increasing the risk of false-positive results
• The potential for alternative diagnostic approaches, such as the use of other tests to evaluate suspected Cushing's syndrome or other conditions requiring accurate assessment of the HPA axis, as discussed in studies such as 1. In clinical practice, it is essential to weigh the potential benefits of inhaled corticosteroids against the potential risks, including their impact on dexamethasone suppression testing, and to consider alternative treatments or diagnostic approaches when necessary, to prioritize morbidity, mortality, and quality of life outcomes.

From the FDA Drug Label

These interactions may interfere with dexamethasone suppression tests which should be interpreted with caution during administration of these drugs

• The FDA drug label does mention that certain interactions may interfere with dexamethasone suppression tests.
• However, it does not specifically mention inhaled corticosteroids (ICS) as a cause of interference.
• The label does discuss various interactions that may affect the results of the dexamethasone suppression test, but it does not provide direct information about the impact of ICS on this test 2. The FDA drug label does not answer the question.

From the Research

Inhaled Corticosteroids and Dexamethasone Suppression Testing

• The relationship between inhaled corticosteroids (ICS) and dexamethasone suppression testing is complex and has been studied in various contexts 3, 4, 5, 6, 7.
• Studies have shown that ICS can affect the hypothalamic-pituitary-adrenal (HPA) axis, which is also assessed by dexamethasone suppression testing 3, 4, 7.
• However, the extent to which ICS interfere with dexamethasone suppression testing is not fully understood and may depend on various factors, such as the type and dose of ICS used 4, 7.
• Some studies suggest that ICS can cause adrenal suppression, which may be detected by dexamethasone suppression testing 4, 6.
• The use of synchronous free cortisol assessment may enhance the interpretation of abnormal dexamethasone suppression test results 5.
• Dexamethasone suppression testing has been shown to predict the later development of impaired adrenal function after a course of prednisone in healthy volunteers 6.

Key Findings

• ICS can affect the HPA axis and cause adrenal suppression 3, 4, 7.
• Dexamethasone suppression testing can detect adrenal suppression caused by ICS 4, 6.
• The interpretation of dexamethasone suppression test results may be influenced by various factors, including the type and dose of ICS used 4, 7.
• Synchronous free cortisol assessment may be useful in enhancing the interpretation of abnormal dexamethasone suppression test results 5.