Oral Vitamin D Substitution Weekly or Monthly and Adherence

Oral Vitamin D Substitution Weekly or Monthly - Which Procedure Leads to Highest Adherence? A Prospective Intervention Study in Outpatient Care

Vitamin D deficiency (defined as 25(OH)-vitamin D serum level <50 nmol/l) is cured with supplementation by mouth. National guidelines recommend the administration of 800 IU cholecalciferol daily for an effective treatment, especially during the winter (poor sun exposition). Commercially available pharmaceutical forms are liquid in Switzerland (drops) and solid forms in Germany (tablets and capsules). Because therapeutic range of vitamin D3 is wide and toxicity is seldom reached, even after the consumption of 200'000 IU, and because the administration of 8 drops daily is inconvenient, weekly and monthly administrations of the cumulative amount (i.e., 5'600 IU weekly or 24'000 IU monthly) have been investigated. Both administration schedules are therapeutic equivalent. The study aims to investigate which form (liquid or solid) and which schedule (weekly or monthly) procure the highest adherence behavior with outpatients under polypharmacy i.e., with 4 or more medications daily. The investigators will use commercially available Swiss and German products.

Intervention study in patients with serum vitamin D <50 nmol/l and polypharmacy, defined as ≥4 medicaments/day. Treatment duration: 6 months. Treatment groups are defined as Lm (liquid monthly 24'000 IU); Lw (liquid weekly 5'600 IU); Sm (solid monthly 20'000 IU) and Sw (solid weekly 5'600 IU). Cross-over design with identical form (liquid or solid) and switching frequence, i.e. from weekly to monthly treatment and vice versa, for 3 months each.

Patient will be recruited by their general practitioners (GP) and allocated to the GP's form (liquid or solid). Patients will be randomly assigned to start weekly or monthly intake for 3 months, and switch to the other frequence for 3 more months.

5'600 IU weekly (1.4 ml oily drops) start for 3 months, will cross-over to 24'000 IU monthly (5 ml alcoholic drops) for the following 3 months.

5'600 IU weekly (1 soft capsule) start for 3 months, will cross-over to 20'000 IU monthly (1 tablet) for the following 3 months.

24'000 IU monthly (5 ml alcoholic drops) start for 3 months, will cross-over to 5'600 IU weekly (1.4 ml oily drops) for the following 3 months.

20'000 IU monthly (1 tablet) start for 3 months, will cross-over to 5'600 IU weekly (1 soft capsule) for the following 3 months.

Patient will start treatment with weekly schedule, and switch after 3 months to monthly schedule for another 3 months.

Patient will start treatment with monthly schedule, and switch after 3 months to weekly schedule for another 3 months.

Patient will start treatment with weekly schedule, and switch after 3 months to monthly schedule for another 3 months.

Patient will start treatment with monthly schedule, and switch after 3 months to weekly schedule for another 3 months.

Taking adherence: number of dosis taken divided by number of dosis prescribed. Timing adherence: number of dosis taken within a time interval (within 15% of the mean preset intake time) divided by number of dosis prescribed.

Inclusion Criteria: vitamin D deficiency by serum level <50 nmol/l polypharmacy defined as 4 daily medicines or more speaking German or Swiss German Exclusion Criteria: hypercalcaemia substitution treatment with cholecalciferol in the past 3 months medication intake provided by a third person and not by the patient himself