Dexamethasone is used principally as an anti-inflammatory or immunosuppressant agent. Because it has only minimal mineralocorticoid properties, the drug is inadequate alone for the management of adrenocortical insufficiency. If dexamethasone is used in the treatment of this condition, concomitant therapy with a mineralocorticoid is also required.
Dexamethasone inhibits pituitary corticotropin (ACTH) release and decreases output of endogenous corticosteroids when given in an amount which does not itself appreciably affect levels of urinary 17-hydroxycorticosteroids. This effect is used in the dexamethasone suppression test for the diagnosis of Cushing's syndrome and the differential diagnosis of adrenal hyperplasia and adrenal adenoma.
Cancer Chemotherapy-induced Nausea and Vomiting
Dexamethasone regimens are used extensively for the prevention of nausea and vomiting associated with emetogenic cancer chemotherapy. To prevent chemotherapy-induced nausea and vomiting associated with chemotherapy regimens with a high emetic risk (i.e., incidence of emesis exceeds 90% if no antiemetics are administered), the American Society of Clinical Oncology (ASCO) currently recommends a 3-drug antiemetic regimen consisting of dexamethasone, aprepitant, and a type 3 serotonin (5-HT3) receptor antagonist (e.g., dolasetron, granisetron, ondansetron, palonosetron, tropisetron [not commercially available in the US]). The antiemetic combination of dexamethasone, aprepitant, and a 5-HT3 receptor antagonist also is preferred in patients receiving combination chemotherapy with an anthracycline and cyclophosphamide. For patients receiving other chemotherapy of moderate emetic risk (i.e., incidence of emesis without antiemetics exceeds 30% but does not exceed 90%), ASCO recommends a 2-drug antiemetic regimen consisting of dexamethasone and a 5-HT3 receptor antagonist. For patients receiving chemotherapy regimens with a low emetic risk (i.e., incidence of emesis without antiemetics exceeds 10% but does not exceed 30%), ASCO recommends dexamethasone alone on the first day of chemotherapy. Antiemetics can be prescribed on an as needed basis in patients receiving chemotherapy with a minimal antiemetic risk (incidence of emesis is less than 10% without antiemetics). For the prevention of delayed emesis in patients receiving cisplatin or other chemotherapy associated with a high emetic risk, these authorities currently recommend a 2-drug combination of dexamethasone and aprepitant.
There is some evidence that short-term adjunctive therapy with IV dexamethasone may decrease the incidence of audiologic and/or neurologic sequelae in infants and children with Haemophilus influenzae meningitis and possibly may provide some benefit in patients with Streptococcus pneumoniae meningitis. The American Academy of Pediatrics (AAP) and other clinicians suggest that use of adjunctive dexamethasone therapy may be considered during the initial 2-4 days of anti-infective therapy in infants and children 6-8 weeks of age or older with known or suspected bacterial meningitis, especially in those with suspected or proven H. influenzae infection. If used, dexamethasone should be initiated before or concurrently with the first dose of anti-infective.