Apr 19, 2011

A 3-Year Holiday From Bisphosphonates Appears Safe

Bone mineral density held steady in women who took a 3-year hiatus from bisphosphonate therapy, according to a new study presented this past weekend at the 20th annual meeting and clinical congress of the American Association of Clinical Endocrinologists (AACE).

“Current AACE guidelines on osteoporosis recommend a drug holiday from bisphosphonates after 4 or 5 years of treatment but the duration of that holiday has not been studied in detail,” Dr. Pauline Camacho, from Loyola University Medical Center in Maywood, Illinois, told Reuters Health.

Among the reasons to stop taking these drugs for awhile is a theoretical concern that long-term suppression of bone remodeling might eventually result in a loss of bone strength.

However, Dr. Camacho points out, “We are stopping the drugs, but we don’t know how long patients should be off of them.”

In 2006, the FLEX study compared patients who discontinued alendronate with those who stayed on the drug and found that those who stopped had a higher fracture risk after 5 years, Dr. Camacho said.

“Therefore the conclusion is you probably should not keep people off of drug for 5 years, but in between, there’s not much knowledge and data about the optimal drug holiday length, so we decided to look at this in a real-world setting,” she said.

In this study, Dr. Camacho and her team reviewed data on 129 osteoporotic and osteopenic patients who started a drug holiday in 2005 or later. The mean patient age was 68 (range 57 to 79), and all but 6 were women. Most (70%) were on alendronate; 21% were taking risedronate and 9% were using ibandronate.

There was no significant change in the mean lumbar spine or femoral neck bone mineral density over 3 years. Specifically, the lumbar spine bone mineral density (in g/cm2) was 1.07 at baseline, 0.97 at year 1, 1.03 at year 2, and 1.13 at year 3. And for the femoral neck, the baseline level and mean changes (again in g/cm2) were 0.80 at baseline, 0.78 at year 1, 0.77 at year 2, and 0.85 at year 3.

Patients did have a significant drop in bone specific alkaline phosphatase (BSAP) 6 months after the bisphosphonates were stopped. However, BSAP levels remained between 8 and 12 mcg/L, the lower end of the premenopausal range, Dr. Camacho said.

“The patients had a mean of about 9 as they started the drug holiday and at the end of 3 years they were still in that range. This is evidence that the skeletal half-life of the bisphosphonates is really long.”

Five fractures occurred during the drug holiday. “These were in patients who had more severe osteoporosis, but our study was not powered to detect fractures, because if you are talking about fractures you need a very large study that definitely should be prospective. In the meantime, I tell my patients that if they fracture, their drug holiday is over,” Dr. Camacho said.

“This study should reassure clinicians that they can leave their patients off for 3 years and they will be fine, but there will be a small number who might fracture,” she said. “If they do fracture, they need to re-start therapy.”

— Fran Lowry, Reuters Health

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