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Pharmacology: Pharmacodynamics: Following topical administration beclomethasone-17,21-dipropionate (BDP) produces potent anti-inflammatory and vasoconstrictor effects.
BDP is a pro-drug with a weak glucocorticoid receptor binding affinity. It is hydrolysed via esterase enzymes to the active metabolite, beclomethasone-17-monoproprionate (B-17-MP), which has high topical anti-inflammatory activity.
BECONASE offers a preventative background treatment for hayfever when taken prior to allergen challenge. After which with regular use, BDP can continue to prevent allergy symptoms from re-appearing by reducing the sensitivity of nasal membranes.
Pharmacokinetics: Absorption: Following intranasal administration of BDP, the systemic absorption was assessed by measuring the plasma concentrations of its active metabolite B-17-MP, for which the absolute bioavailability following intranasal administration is 44%.
Following oral administration of BDP, the systemic absorption was also assessed by measuring the plasma concentrations of its active metabolite, B-17-MP, for which the absolute bioavailability following oral administration is 41%.
Metabolism: BDP is cleared very rapidly from the circulation and plasma concentrations are undetectable (<50 pg/mL) following oral or intranasal dosing. Metabolism is mediated via esterase enzymes found in most tissues. The main product of metabolism is the active metabolite (B-17-MP). Minor inactive metabolites, beclomethasone-21-monopropionate (B-21-MP) and beclomethasone (BOH), are also formed but these contribute little to systemic exposure.
Distribution: The tissue distribution at steady-state for BDP is moderate (20 L) but more extensive for B-17-MP (424 L). Plasma protein-binding is moderately high (87%).
Elimination: The elimination of BDP and B-17-MP are characterised by high plasma clearance (150 and 120 L/hr) with corresponding terminal elimination half-lives of 0.5 h and 2.7 h. Following oral administration of titrated BDP, approximately 60% of the dose was excreted in the faeces within 96 hours mainly as free and conjugated polar metabolites. Approximately 12% of the dose was excreted as free and conjugated polar metabolites in the urine. The renal clearance of BDP and its metabolites is negligible.
