Importance of calcium co-medication in bisphosphonate therapy of osteoporosis - An approach to improving correct intake and drug adherence

Background and objective: In all of the large, pivotal, multicentre trials of bisphosphonate therapy, patients have received added calcium in amounts ranging from 500 to 1000 mg/day above individual dietary intake. Accordingly, calcium supplements or calcium/vitamin D combinations are currently recommended as co-medication with anti-resorptive therapy in all recently published guidelines on the treatment of osteoporosis. However, the consistent use or effectiveness of calcium may be impaired by several factors in the individual patient, including low prescription rate or lack of advice to purchase calcium, reduced adherence because of the complexity of the regimen, and incorrect intake (e.g. taking calcium with bisphosphonates at the same time). Patients with osteoporosis who adhere to drug therapy experience a significantly lower fracture rate. Therefore, there is a need to improve correct intake of bisphosphonates together with calcium supplementation, which may enhance adherence. The dosage regimen could be simplified by providing the two compounds in an integrated pack. Such a pack, containing one tablet of risedronic acid and six calcium carbonate tablets (Actonel (R), Procter & Gamble Pharmaceuticals, Weiterstadt, Germany), has been developed to facilitate correct intake. In this study, the impact of this fixed-combination pack on patient understanding of dosing instructions and on preference was tested by comparing the fixed combination with separate risedronic acid and calcium packages. Patients and methods: A new blister strip was developed containing one tablet of risedronic acid 35mg and six tablets of calcium carbonate 1250mg (500mg elemental calcium), representing I week of therapy; the control was the same medications in separate packaging. The study was conducted in a cohort of 164 postmenopausal women (mean age 69 years). Half of the participants were bisphosphonate users (n = 83). The combined understanding of five instructions risedronic acid intake in the morning, only with water, without food, without other medication, and separate from calcium - was tested in a crossover design. Participants were also asked to state their preference for the combination packaging versus separate packs. Results: Understanding of the five instructions for the separate packaging was 70%. The combination pack significantly improved understanding of these instructions to 80% (p < 0.05). Eighty-three percent of participants preferred the combination pack over separate packs (p < 0.05). The most frequently given reasons for preferring the combination pack were prefer one pack over two packs, easy/convenient to use/practical/handy, easy to understand/less confusion, and easier to remember/less likely to forget. Conclusions: The availability of a fixed-combination pack of risedronic acid 35 mg/week and calcium tablets can increase the likelihood that postmenopausal osteoporotic patients will receive both a bisphosphonate and calcium, which in turn is likely to enhance the correct intake of combination therapy.