Men's Osteoporosis Support Group

Once- or twice-monthly Actonel

Bone. 2008 Jan;42(1):36-42. Epub 2007 Sep 8, Efficacy and safety of risedronate 150 mg once a month in the treatment of postmenopausal osteoporosis. Delmas PD and others. PMID: 17920005. This study involving only post-menopausal women compared the effectiveness of 5 mg/day Actonel (risedronate) versus 150 mg Actonel taken once-monthly followed by daily placebo for the remainder of the month during a two-year period. There were 642 women in the 5 mg/day group and 650 in the 150 mg/month group. Bone mineral density, bone turnover markers, fractures, and adverse events were evaluated. The authors found the once-monthly dosing to be non-inferior to the daily dose. The safety of the two regimens was considered overall to be similar. They concluded: "Risedronate 150 mg once a month is similar in efficacy and safety to daily dosing and may provide an alternative for patients who prefer once-a-month oral dosing."

This trial is a follow up to one that used a similar protocol to test the effectiveness of 75 mg of Actonel taken on two consecutive days each month. The findings were the same in this study with the two consecutive day dosing also non-inferior to the 5 mg/day dose. See: Osteoporos Int. 2007 Dec 18 [Epub ahead of print], Monthly dosing of 75 mg risedronate on 2 consecutive days a month: efficacy and safety results. Delmas PD and others. PMID: 18087660. The authors note that the comparable effectiveness with once- or twice-monthly dosing is due to the ability of bisphosphonates (which includes Fosmax, Actonel and Boniva) to exert a sustained effect on bone metabolism because they adhere to bone for long intervals. Fosamax and Actonel were first once-daily dosed, then once-weekly. In the mean time Boniva had been approved for once-monthly dosing. This Delmas and others study appears to back the use of Actonel on the same dosing schedule.

Note that this study did not determine statistically significant better results, rather the result was of non-inferiority. This occurs when a new dosing regimen goes head to head with a previously approved medication's dose schedule. So the investigators did not compare the results to placebo, which would conclude statistically significant results. In short, bone mineral density (BMD) change is an appropriate endpoint when evaluating a new dosing schedule of a bisphosphonate for which a fracture benefit has already been established.

One interesting other study referred to in this research is one which found no loss of effectiveness with Actonel over a seven-year period of its use with the 5 mg/day dose method. See: Calcif Tissue Int. 2004 Dec;75(6):462-8. Epub 2004 Oct 7. Seven years of treatment with risedronate in women with postmenopausal osteoporosis. Mellstrom DD and others. PMID: 15455188.

Editor's comments. For individuals who find the once-weekly dose regimen inconvenient, this monthly dosing regimen could be beneficial. I recommend you speak to your physician to see if he/she agrees that you should switch to this if you are currently on the once-weekly Actonel dose. If you are only getting your medication once a month, you would want to be sure you took it exactly according to recommendations. For instance, should you take it with food or other medicines this might mean negating the benefit entirely. Whereas, on the once-weekly dose, if you make a mistake once during the month when taking your Actonel, you would still benefit from the three other doses that were taken correctly. This regimen has not gotten FDA approval to my knowledge and would be taken as an off-label method I assume. I'm unaware of any similar research with Fosamax, but one would expect equal results on a once-monthly dose which would have to be 280 mg. You'd definitely want to discuss this with your physician if you are considering it. With osteonecrosis of the jaws as a rare but possible side effect from oral bisphosphonates, I would be hesitant to try dosing regimens that hadn't been tested in clinical trials. See this recent Update for more information and links to other articles on this topic.

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