Betamethasone is a topical steroid. It reduces or inhibits the actions of chemicals in the body that cause inflammation, redness, and swelling. Betamethasone topical is used to treat inflammation caused by a number of conditions such as allergic reactions, eczema, and psoriasis. Betamethasone is in a class of drugs called steroids. Betamethasone reduces swelling and decreases the body's immune response.
Betamethasone is used to treat many different conditions. It is used to treat endocrine (hormonal) disorders when the body does not produce enough of its own steroids. It is also used to treat many immune and allergic disorders, such as arthritis, lupus, psoriasis, asthma, ulcerative colitis, and Crohn's disease. Betamethasone is a synthetic corticosteroid and is used to decrease inflammation. It works by acting within cells to prevent the release of certain chemicals that are important in the immune system. These chemicals are normally involved in producing immune and allergic responses, resulting in inflammation. By decreasing the release of these chemicals in a particular area, inflammation is reduced. This can help control a wide number of disease states, characterised by excessive inflammation. They include severe allergic reactions, inflammation of the lungs in asthma and inflammation of the joints in arthritis.
Betamethasone also decreases the numbers of white blood cells circulating in the blood. This, along with the decrease in inflammatory chemicals, can prevent the rejection of organ transplants, as it prevents the body from attacking foreign tissue. It is useful for the treatment of certain types of leukaemia, where there is an abnormally large production of certain white blood cells. It is also used to treat some diseases which are caused by the immune system attacking itself (auto immune diseases).
Betamethasone is a group II (potent) topical corticosteroid. This classification ranks the potency of topical corticosteroids from I to IV, with I being the most potent. The more potent the topical corticosteroid the greater the efficacy of the preparation, however, this also increases the risk of any systemic side effects associated with the topical absorption of the corticosteroid. Sufficient corticosteroids may be absorbed through the skin to give rise to systemic side effects. The extent of absorption is determined by many factors including the vehicle, the presence of broken skin and the use of occlusive dressings. Topical corticosteroids can be absorbed through normal intact skin.
The esterification of the betamethasone steroid nucleus at the C17 position with valerate minimises the absorption of the molecule through the skin. This increase the topical potency of the steroid whilst decreasing the possibility of absorption through the skin and any systemic side effects. It is possible that topically administered betamethasone valerate can produce systemic side effects mimicking those of the orally administered parent compound betamethasone.
Betamethasone has relatively high glucocorticoid activity (anti-inflammatory effects) with insignificant mineralocorticoid activity (effects on the fluid and electrolyte balance). Systemic glucocorticoid effects are described under ADVERSE EFFECTS. The risk of systemic glucocorticoid effects is significantly less with topically administered betamethasone valerate than with the oral administration of the parent compound (betamethasone). It has been estimated the application of more than 100g of 0.1%w/w betamethasone valerate to the skin in one week is likely to cause adrenal suppression. The systemic absorption of betamethasone valerate can occur in situations when it is applied to large areas of the body, thin skin, open lesions, or is covered by an occlusive dressing. Once absorbed through the skin the pharmacokinetics of topical corticosteroids are similar to those of the systemically administered parent compound. Betamethasone valerate is metabolised in the liver to yield the parent compound. Corticosteroids are bound to plasma proteins in varying degrees, mainly to globulin and to a lesser extent to albumin. Betamethasone is 64% bound to plasma proteins. Only the unbound form of betamethasone valerate has pharmacological effects, or is metabolised. The half life of orally administered betamethasone is 5.6 hours. Betamethasone is primarily metabolised in the liver, and then excreted via the kidneys, only 5% of betamethasone is excreted unchanged in the urine.