|Systematic (IUPAC) name|
|(8S,9R,10S,11S,13S,14S,16R,17R)-9- Fluoro-11,17-dihydroxy-17-(2-hydroxyacetyl)-10,13,16- trimethyl-6,7,8,9,10,11,12,13,14,15,16,17- dodecahydro-3H-cyclopenta[a]phenanthren-3-one|
|ATC code||A01 C05, D07, H02, R01, S01, S02, S03|
|Mol. mass||392.461 g/mol|
|Half life||36-54 hours|
|Legal status||℞ Prescription only|
|Routes||Oral, IV, IM, SC and IO|
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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.
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 useful to counteract allergic anaphylactic shock, if given in high doses. It is present in certain eye drops – particularly post-eye surgery drops – and as a nasal spray (trade name Dexacort), and ear certain ear drops (Sofradex, when combined with an antibiotic and an antifungal).
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.
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 lenalidomide, 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.
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 CYP21 (CYP21A2) 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.
In adrenal insufficiency and Addison's disease, dexamethasone is prescribed when the person doesn't respond well to prednisone or methylprednisone.
Dexamethasone may be given to women at risk of delivering prematurely in order to promote maturation of the fetus' lungs. This has been associated with low birth weight, although not with increased rates of neonatal death.
Dexamethasone is used in the treatment of high altitude cerebral edema as well as pulmonary edema. It is commonly carried on mountain climbing expeditions to help climbers deal with altitude sickness.
Dexamethasone is also used in a diagnostic context, namely in its property to suppress the natural pituitary-adrenal axis. Patients presenting with clinical signs of glucocorticoid excess (Cushing's syndrome) are generally diagnosed by a 24-hour urine collection for cortisol or by a dexamethasone suppression test. During the latter, the response of the body to a high dose of glucocorticoids is monitored. Various forms are performed. In the most common form, a patient takes a nighttime dose of either 1 or 4 mg of dexamethasone, and the serum cortisol levels are measured in the morning. If the levels are relatively high (over 5 µg/dL or 150 nmol/L), then the test is positive and the patient has an autonomous source of either cortisol or ACTH, indicating Cushing's syndrome where the tumor does not have a feedback mechanism. If ACTH levels are lowered by at least 50%, this would indicate Cushing's Disease, since the pituitary adenoma has a feedback mechanism that has been reset to a higher level of cortisol. Longer versions rely on urine collections on oral dexamethasone over various days.
Combined with marbofloxacin and clotrimazole, dexamethasone is available under the name Aurizon , CAS number 115550-35-1, and used to treat difficult ear infections, especially in dogs. It can also be combined with Trichlormethiazide to treat horses with swelling of distal limbs and general bruising.
Some of these contraindications are relative:
If dexamethasone is given orally or by injection (parenteral) over a period of more than a few days, side-effects common to systemic glucocorticoids may occur. These may include:
Other side-effects have been noted, and should cause concern if they are more than mild.
The short time treatment for allergic reaction, shock, and diagnostic purposes usually does not cause serious side effects.
Other interactions (with certain antibiotics, estrogens, ephedrine, digoxin) are known.
In 2005, Polish cross country skier Justyna Kowalczyk was disqualified from the Under 23 (U23) OPA (Alpine nations) Intercontinential Competition in Germany and issued a 2-year suspension for her doping offenses on dexamethasone. This was eventually reduced to one year during 2005 and later rescinded by the Court of Arbitration for Sport in December 2005. She would later earn a bronze in the women's 30 km freestyle mass start at the 2006 Winter Olympics in Turin.