Dexamethasone is a potent synthetic member of the glucocorticoid class of steroid hormones. It acts as an anti-inflammatory and immunosuppressant. Its potency is about 20-30 times that of hydrocortisone and 4-5 times of prednisone.

Anti-inflammatory

Dexamethasone is used to treat many inflammatory and autoimmune conditions, e.g., rheumatoid arthritis.

It is also given in small amounts (usually 5-6 tablets) before and/or after some forms of dental surgery, such as the extraction of the wisdom teeth, an operation which often leaves the patient with puffy, swollen cheeks.

It is injected into the heel when treating plantar fasciitis, sometimes in conjunction with triamcinolone acetonide.

It is useful to counteract allergic anaphylactic shock, if given in high doses. It is present in certain eye drops and as a nasal spray (trade name Dexacort).

Dexamethasone is used in transvenous screw-in cardiac pacing leads to minimize the inflammatory response of the myocardium. The steroid is released into the myocardium as soon as the screw is extended and can play a significant role in minimizing the acute pacing threshold due to the reduction of inflammatory response. The typical quantity present in a lead tip is less than 1.0 mg.

Dexamethasone is often administered before antibiotics in cases of bacterial meningitis. It then acts to reduce the inflammatory response of the body to the bacteria killed by the antibiotics (bacterial death releases pro-inflammatory mediators that can cause a response which is harmful to the patient), thus improving prognosis and outcome.

Oncologic uses

In oncology, it is given to cancer patients undergoing chemotherapy, to counteract certain side-effects of their antitumor treatment. Dexamethasone can augment the antiemetic effect of 5-HT₃ receptor antagonists like ondansetron. Dexamethasone is also used in certain hematological malignancies, especially in the treatment of multiple myeloma, in which dexamethasone is given alone or together with thalidomide (thal-dex) or a combination of Adriamycin (doxorubicin) and vincristine (VAD). In brain tumours (primary or metastatic), dexamethasone is used to counteract the development of edema, which could eventually compress other brain structures. Dexamethasone is also given in cord compression where a tumor is compressing the spinal cord.

Endocrine

Dexamethasone can be used in the context of congenital adrenal hyperplasia, to prevent virilisation of a female fetus. If one or both parents are carriers of mutations to the CYP21A gene, the mother may start dexamethasone treatment within 7 weeks of conception. At the 12th week, a chorionic villus sample will determine whether the fetus is male (in which case the dexamethasone is stopped) or female. Subsequent DNA analysis can then reveal whether the female fetus is a carrier of the mutation, in which case dexamethasone treatment must continue until birth. The side-effects for the mother can be severe and the long-term impact on the child is not clear.