Effect of orally administered beclomethasone dipropionate on calcium absorption from the gut in normal subjects

BACKGROUND--There is evidence that patients with chronic obstructive airways disease and asthma who take inhaled steroids have a low bone density. As most of a drug given from a metered dose inhaler is actually swallowed, the possibility that swallowed beclomethasone dipropionate acts topically in the gut to impair calcium absorption was investigated. Such an effect, if sustained, may be a causative factor of long term bone loss. METHODS--A two week randomised, double blind, placebo controlled, crossover trial was performed in 12 normal volunteers. Subjects were randomly allocated to swallow beclomethasone dipropionate capsules (500 micrograms twice a day) or placebo for one week. The alternate capsule was given throughout the second week. At the end of each week, calcium absorption was assessed by a strontium absorption test. Serum parathyroid hormone, plasma calcium, and plasma phosphate concentrations were determined on the last two days of each week. Twenty four hour urinary calcium, hydroxyproline, and cortisol concentrations were measured for four successive days in each week. RESULTS--All subjects completed the study. There was a 12% reduction in strontium absorption during the beclomethasone dipropionate ingestion week. There was also a 23% reduction in 24 hour urinary cortisol excretion during the same week. CONCLUSIONS--Calcium absorption (measured by a strontium absorption test) was reduced by oral administration of beclomethasone dipropionate for one week. Decreased calcium absorption due to swallowed corticosteroid may contribute to side effects of inhaled steroids and further long term studies are needed.