Dexamethasone sodium phosphate EP Impurity B

Absorption

An intramuscular injection of 3mg betamethasone acetate and 3mg betametasone phosphate reaches a betamethasone Cmax 33.21 ± 8.71 ng/mL, with a Tmax of 1.56 ± 1.32 h, and an AUC of 506.95 ± 125.03 ng*h/mL.

Toxicity

Patients experiencing an acute overdose should be treated with symptomatic and supportive treatment. Chronic overdoses where patients require continued therapy can be treated through temporary dose reduction or alternate day treatment.
The oral, intraperitoneal, and intravenous LD50 values in rats are 1877 mg/kg, 1179 mg/kg, and 1276 mg/kg, respectively.

Originator

Bentelan,Biofutura

The Uses of Dexamethasone sodium phosphate EP Impurity B

Glucocorticoid.

Indications

Betamethasone phosphate is indicated intramuscularly to treat allergic states, dermatologic diseases, endocrine disorders, gastrointestinal diseases, hematologic disorders, neoplastic diseases, nervous system conditions, ophthalmic diseases, renal diseases, respiratory diseases, rheumatic disorders, trichinosis with neurologic or myocardial involvement, and tuberculous meningitis with subarachnoid block or impending block. It is also used intra-articularly in the treatment of acute gouty arthritis, acute and subacute bursitis, acute nonspecific tenosynovitis, epicondylitis, rheumatoid arthritis, and synovitis of osteoarthritis. Intralesional betamethasone phospahte is indicated in the treatment of alopecia areata, discoid lupus erythematosus, keloids, lichen planus, lichen simplex chronicus, psoriatic plaques, necrobiosis lipoidica diabeticorum, and localized hypertrophic, infiltrated, inflammatory lesions of granuloma annulare.

Background

Betamethasone phosphate is a prodrug that is rapidly hydrolyzed, providing rapidly accessible betamethasone to agonize glucocorticoid receptors. Betamethasone provides greater anti-inflammatory activity than prednisolone with less sodium and water retention.
Betamethasone sodium phosphate was granted FDA approval on 3 March 1965.

Definition

ChEBI: Betamethasone phosphate is a steroid phosphate that is the 21-O-phospho derivative of betamethasone. It has a role as an anti-inflammatory agent and an immunosuppressive agent. It is a steroid phosphate, an 11beta-hydroxy steroid, a fluorinated steroid, a 17alpha-hydroxy steroid, a 20-oxo steroid, a 3-oxo-Delta(1),Delta(4)-steroid and a tertiary alpha-hydroxy ketone. It is functionally related to a betamethasone. It is a conjugate acid of a betamethasone phosphate(2-).

Manufacturing Process

A solution of bistriethylamine phosphate was prepared by slowly adding 2.36 ml of 85% phosphoric acid to 20 ml of acetonitrile containing 9.9 ml, of triethylamine at 20°C. This solution was added to a stirred mixture of 4.70 g of 9α-fluoro-11β,17α,21-trihydroxy-16α-methyl-1,4-pregnadiene-3,20-dione 21-methanesulfonate and 20 ml of acetonitrile. The mixture was heated under reflux for 4 h and then evaporated under reduced pressure to a volume of 12 ml. This mixture was a concentrated solution of 9α-fluoro-11β,17α,21- trihydroxy-16α-methyl-1,4-pregnadiene-3,20-dione 21-phosphate triethylamine salt with some inorganic phosphate.
The salt of 9α-fluoro-11β,17α,21-trihydroxy-16α-methyl-1,4-pregnadiene- 3,20-dione 21-phosphate may be converted to 9α-fluoro-11β,17α,21- trihydroxy-16α-methyl-1,4-pregnadiene-3,20-dione 21-phosphate by treatment with acid (for example HCl).

brand name

Celestone (Schering).

Therapeutic Function

Glucocorticoid

Pharmacokinetics

Corticosteroids bind to the glucocorticoid receptor, inhibiting pro-inflammatory signals, and promoting anti-inflammatory signals. Betamethasone phosphate has a short duration of action as it is rapidly hydrolyzed to betamethasone. Corticosteroids have a wide therapeutic window as patients may require doses that are multiples of what the body naturally produces. Patients taking corticosteroids should be counselled regarding the risk of hypothalamic-pituitary-adrenal axis suppression and increased susceptibility to infections.

Metabolism

Betamethasone phosphate is rapidly de-esterified to betamethasone.