study of the effect of vitamin d as an add-on therapy to corticosteroids in asthma

Conditions: Asthma

Summary: the purpose of the study is to find out if taking vitamin d in addition to an asthma controller medication helps to prevent worsening of asthma symptoms and asthma attacks.

this is a randomized, double-blind parallel group trial that will enroll individuals who have vitamin d insufficiency and asthma with persistent symptoms despite low-dose inhaled corticosteroid. participants on low-dose inhaled corticosteroid will be randomized to add-on therapy with either placebo or high-dose vitamin d for a 28-week period. during the inhaled corticosteroid-stable phase, participants will remain on low-dose inhaled corticosteroid. during the inhaled corticosteroid-taper phase, participants will taper their inhaled corticosteroid by 50% at two time-points post-randomization. the investigators will determine if the addition of vitamin d reduces the likelihood of treatment failure when compared to placebo during both the inhaled corticosteroid-stable and inhaled corticosteroid-taper phases of the study. given the high prevalence of both vitamin d insufficiency and asthma, this trial has high potential to impact daily asthma management.

Eligibility criteria:
inclusion criteria: * men and women 18 years of age and older * physician-diagnosed asthma for at least previous 12 months * asthma confirmed by: (a) β-agonist reversibility of forced expiratory volume in 1 second (fev1) ≥12 % following 180 mcg (4 puffs) levalbuterol at visit 1 or (b) methacholine provocative concentration causing a 20% fall in fev1 (pc20) ≤ 8 mg/ml if not receiving an inhaled corticosteroid or ≤ 16 mg/ml if receiving an inhaled corticosteroid at visit 2. source documentation for pc20 from an asthmanet methacholine challenge completed within 6 months of visit 2 will be accepted. * stable asthma controller therapy (inhaled corticosteroid or leukotriene modifier only) dose for past 2 weeks * fev1 ≥ 50% of predicted at visit 1 * vitamin d level of less than 30 ng/ml at visit 0 * experienced no more than one treatment failure in the vida run-in or oral corticosteroid (ocs) response periods on previous enrollments * for women of childbearing potential: not pregnant, non-lactating, and agree to practice an adequate birth control method for the duration of the study exclusion criteria: * taking vitamin d supplements containing \> 1000 iu/day of vitamin d * taking \>2500 mg/day calcium supplements * chronic oral corticosteroid therapy * chronic inhaled corticosteroid therapy \> 1,000 mcg of fluticasone daily or the equivalent * history of physician-diagnosed nephrolithiasis * use of concomitant medications that alter vitamin d metabolism - phenytoin, phenobarbital, cardiac glycosides; or absorption - orlistat, cholestyramine, colestipol; or those that interfere with study endpoints * impaired renal function (gfr \< 30 ml/min) * asthma exacerbation within past 4 weeks requiring systemic corticosteroids * respiratory tract infection within past 4 weeks * chronic diseases (other than asthma) * history of cigarette smoking within the past 1 year or \> 10 pack years total * serum calcium greater than 10.2 mg/dl on entry * urine calcium/creatinine ratio greater than 0.37 (urinary ca and creat in mg)

Keywords: asthma vitamin d corticosteroids treatment failure