Alendronate with cholecalciferol (Fosamax Plus): new formulation contains more vitamin D

Published in NPS RADAR

Date published: About this date

Clinical content may change after this date. This information is not intended as a substitute for medical advice from a qualified health professional. Health professionals should rely on their own expertise and enquiries when providing medical advice or treatment.

A new formulation of alendronate with cholecalciferol (Fosamax Plus) containing a higher cholecalciferol dose was PBS listed in August 2008.

The new formulation contains 5600 units in a once-weekly dose, equivalent to 800 units per day. The previous formulation contained cholecalciferol 2800 units, equivalent to 400 units per day. The lower-dose formulation will be gradually phased out by the manufacturer, but stock in pharmacies may vary.

The dose of vitamin D in Fosamax Plus is not intended to treat vitamin D deficiency

When prescribing Fosamax Plus, consider the risk of vitamin D deficiency. If deficiency is suspected, test the serum 25-hydroxyvitamin D (25-OHD) concentration. The correct dose of cholecalciferol depends on the extent of vitamin D deficiency (or insufficiency). Treat moderate to severe deficiency (25-OHD ≤ 25 nmol/L) with high-dose supplements of 3000–5000 units daily for 6–12 weeks, until normal levels are achieved.1 A maintenance dose of around 1000 units daily is then required — possibly indefinitely. 1,2 Current recommendations are to maintain serum 25-OHD concentration above 50 nmol/L.1,2

The cholecalciferol content of Fosamax Plus is not intended to correct moderate to severe vitamin D deficiency.3 It may help improve vitamin D levels in patients with mild deficiency (serum 25-OHD concentration of 37.5–50 nmol/L3,4) and/or inadequate sunlight exposure.5

Ensure adequate vitamin D and calcium for people with osteoporosis. For people with inadequate sun exposure at least 800–1000 units per day is recommended. Higher-dose supplements may be indicated in some cases (up to 2000 units per day).2,5 However, vitamin D supplementation does not clearly benefit people with osteoporosis who have normal vitamin D status — there is no reason to switch such patients from alendronate to the combination product.

A similar dose of vitamin D is PBS subsidised in a combination formulation of risedronate (Actonel Combi D) which includes sachets of calcium and vitamin D3 880 units for use on 6 days of the week. Fosamax Plus contains cholecalciferol formulated in the same tablet as alendronate.

The NPS RADAR review for this medicine was updated online in December 2008. Visit to read the full review.


  1. Vitamin D and adult bone health in Australia and New Zealand: a position statement. Med J Aust 2005;182:281–5. [PubMed]
  2. eTG complete [CD-ROM]. Melbourne: Therapeutic Guidelines Ltd, July 2008.
  3. Merck Sharp and Dohme (Australia) Pty Ltd. Fosamax Plus Once Weekly Product Information. May 2008.
  4. Recker R, Lips P, Felsenberg D, et al. Alendronate with and without cholecalciferol for osteoporosis: results of a 15-week randomized controlled trial. Curr Med Res Opin 2006;22:1745–55. [PubMed]
  5. Osteoporosis Australia. Calcium, vitamin D and osteoporosis. A Guide for GPs. 2nd Edition. 2008. (accessed 28 October 2008).