Dexamethasone
Highly Potent Synthetic Glucocorticoid: Effects, Indications and Notes
Dexamethasone is a synthetic glucocorticoid that has been used in medicine for decades. It belongs to the corticosteroid group and is distinguished by a particularly high anti-inflammatory potency. Compared with endogenous cortisol, dexamethasone acts considerably more potently and with a longer duration of action. It frequently serves as the reference substance for glucocorticoid potency in pharmacological comparisons.
Mechanism of Action
As a glucocorticoid, dexamethasone binds to intracellular glucocorticoid receptors. The resulting complex migrates into the cell nucleus and influences gene expression. This inhibits the production of pro-inflammatory mediators such as prostaglandins, leukotrienes and cytokines. Simultaneously, anti-inflammatory proteins are synthesised in greater quantities.
The immunosuppressive component of dexamethasone affects primarily the cellular immune response. T-lymphocyte activity is inhibited and interleukin secretion is reduced. This makes the compound pharmacologically relevant in both inflammatory reactions and unwanted immune reactions.
Compared with prednisolone, dexamethasone has approximately six times greater glucocorticoid potency. Its mineralocorticoid activity is, however, very low, which reduces sodium retention and associated fluid retention compared with other corticosteroids. The half-life of dexamethasone is longer than that of short-acting glucocorticoids such as prednisolone, which allows once-daily dosing in certain situations.
Indications
Dexamethasone is used across a broad spectrum of medical disciplines. Indications encompass both acute and chronic conditions from various specialties.
Inflammatory Conditions
In severe inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus or inflammatory bowel disease, dexamethasone may be used as part of a medically supervised treatment regimen. It is also used in acute allergic reactions and severe bronchial asthma. In dermatology it is applied in certain inflammatory skin conditions when topical therapies are insufficient.
Neurological Applications
In neurology, dexamethasone is used to reduce cerebral oedema, for example in brain tumours, brain metastases or after neurosurgical procedures. Its anti-oedematous effect on inflamed tissue is of clinical importance. In bacterial meningitis, dexamethasone is used adjunctively to reduce inflammation-related complications.
Oncological Applications
In oncology, dexamethasone is one of the most frequently used concomitant medications. It is employed for the prevention of nausea and vomiting in the context of chemotherapy and for the treatment of certain haematological conditions. In the treatment of multiple myeloma, it is a component of established protocols. In certain malignancies it may also be part of the treatment itself, since lymphoma and myeloma cells can be susceptible to glucocorticoids.
Ophthalmology
In ophthalmology, dexamethasone is used as eye drops or eye ointment in inflammatory eye conditions not caused by infections. It is also available as an intravitreal implant for certain retinal disorders.
Diagnostic Application
The dexamethasone suppression test serves as a diagnostic tool for investigating Cushing's syndrome. It exploits the negative-feedback suppression of cortisol secretion by exogenous glucocorticoid. In a normally functioning regulatory system, cortisol secretion is suppressed after dexamethasone administration, whereas in Cushing's syndrome this suppression is absent or incomplete.
Intensive Care
Dexamethasone gained wide recognition through clinical study results in severely ill COVID-19 patients. Clinical trials demonstrated improved survival in patients requiring mechanical ventilation. In intensive care, the compound is also used in other severe inflammatory states.
Formulations and Dosage
Dexamethasone is available in various formulations: tablets, injection solutions, eye drops and eye ointments, nasal sprays and as an intravitreal implant. Dosage depends on the indication, severity of the condition and the individual patient response. It is always determined by a physician and adjusted individually. For systemic use, dosage varies across a wide range depending on the indication.
Notes on Administration
For prolonged systemic use, medical supervision is required. Abrupt discontinuation after prolonged treatment should be avoided, as endogenous cortisol production may have been suppressed by exogenous glucocorticoid administration. Gradual dose tapering is medically necessary in such situations.
Caution is required in infectious diseases, as the immunosuppressive effect may impair the body's defence response. Latent infections such as tuberculosis may be reactivated under glucocorticoid therapy. Patients with diabetes mellitus should be aware that glucocorticoids can raise blood glucose levels.
Adverse Effects
With short-term use at low doses, the side-effect profile of dexamethasone is generally manageable. With higher doses or longer duration of use, various undesirable effects may occur:
- Elevated blood glucose (risk of steroid diabetes)
- Weight gain and redistribution of body fat (truncal obesity, moon face)
- Reduced bone density (osteoporosis) with long-term use
- Increased infection risk due to immunosuppression
- Mood changes, sleep disturbances and, in rare cases, steroid psychosis
- Elevated intraocular pressure (glaucoma risk) and lens opacity (cataract)
- Suppression of endogenous cortisol production (adrenal suppression)
- Delayed wound healing and skin atrophy
- Elevated blood pressure with prolonged use
Drug Interactions
Dexamethasone can interact with various medicinal products. Non-steroidal anti-inflammatory drugs (NSAIDs) may increase the risk of gastrointestinal bleeding when combined with dexamethasone. Certain antibiotics, antifungals and antiviral agents can influence the metabolism of dexamethasone via hepatic enzymes. Conversely, dexamethasone itself can act as an inducer of liver enzymes, accelerating the breakdown of other medications. A complete medication history is important before starting therapy.
Contraindications
Dexamethasone should not be used in known hypersensitivity to the compound. Systemic infections that are not adequately treated also represent an important restriction. During vaccination with live vaccines, caution is required during immunosuppressive therapy, as the immune response to the vaccine may be impaired.
Frequently Asked Questions
How does dexamethasone differ from cortisone?
Cortisone is the inactive precursor of cortisol and must first be converted to cortisol in the body to become active. Dexamethasone, in contrast, is a synthetic glucocorticoid that is present directly as an active compound and does not require prior activation. The glucocorticoid potency of dexamethasone is considerably higher: while 1 mg prednisolone is approximately equivalent to 0.15 mg dexamethasone, 20 mg cortisol corresponds to 0.75 mg prednisolone. These potency differences are clinically relevant for dosing.
Why is dexamethasone important in brain metastases?
Brain metastases can cause neurological symptoms such as headache, nausea and impaired consciousness through oedema and mass effect. Dexamethasone can rapidly reduce peritumoral oedema and thereby relieve symptoms. In this situation it is often a bridging measure until definitive oncological therapy can be initiated. Dosage and duration are individually determined.
Can dexamethasone be stopped abruptly?
After short-term high-dose therapy over a few days, rapid discontinuation is generally possible. After prolonged treatment, dexamethasone must be gradually tapered because the adrenal glands reduce their own cortisol production during therapy. Abrupt discontinuation after long-term therapy can lead to an adrenal crisis. The exact approach to discontinuation is always determined by the treating physician.