Evidence for pharmacological treatment of SLOP includes 3 RCTs (Zehnder et al. 2004; Bauman et al. 2005b; Moran de Brioto et al. 2005) (n=124 participants). In these studies, the treatment group experienced improvement or maintenance in bone health at various sites. For the two studies that tested Alendronate, the extent of improvement was greater in the study by Zehnder et al. (2004) who found an increase in BMD at the spine with maintenance of BMD at the hip and tibia. In contrast, Moran de Brioto et al. (2005) only found a non-significant increase in BMD in the upper extremity and a significant increase in total BMD. The difference in response of outcomes could be a result of the younger participants with less severe injuries in the work by Zehnder and coworkers (2004). Bauman and colleagues noted positive results in leg BMD for participants who received vitamin D.
This review has provided conflicting support for using first and second generation oral bisphosphonates for prevention of low bone mass and some support for treatment of low bone mass. Despite the benefits of these medications, they are not without their complications. Oral bisphosphonates must be ingested on an empty stomach, with 4-8oz of water, followed by sitting up for one-hour post ingestion, prior to taking any other food or medication. About 1% of the ingested oral bisphosphonate is absorbed in the upper intestine, yet it remains in the body in an inactive form for several months or years thereafter. Oral bisphosphonate therapy can cause side effects; joint pain, stomach upset and diarrhea being the most frequently reported adverse effects. Intravenous formulations of bisphosphonates are available in monthly, quarterly and annual preparations, and have a greater relative potency. Although their common short-term side effects include fever, low serum calcium and transient decrease in white blood cells, IV preparations are attractive due to the flexibility in dosing regimens, assured adherence to therapy and the reduced relative risk of an adverse upper gastrointestinal event.
Bisphosphonates should be used with caution in pre-menopausal women due to the unknown teratogenic effects of these medications on the fetus during pregnancy. Patients taking acetylsalicylic acid (ASA), corticosteroids or NSAIDS may require gastrointestinal prophylaxis as these medications in combination with bisphosphonates increase the relative risk of developing a gastric ulcer or bleeding. Many questions regarding the safety of these medications among people with SCI and the optimal duration of therapy remain. Zolendronate, an IV bisphosphonate, has been reported to increase the incidence of serious atrial fibrillation resulting in hospitalization or disability among 1-3% of elderly non-SCI patients (HORIZON study, Black et al. 2007). Zolendronate should be used with caution in elderly patients or patients with premorbid atrial fibrillation or arrhythmia secondary to autonomic dysfunction after SCI. The risk of osteonecrosis of the jaw is highest among people with a prior history of cancer or radiotherapy. Both osteonecrosis of the jaw and arrhythmia should be discussed during consent for oral or IV bisphosphonate therapy.
It has been shown that oral bisphosphonates may be taken safely without adverse effects on bone metabolism for 10 years in postmenopausal women (Bone et al. 2004). Data from postmenopausal non-SCI women suggests BMD should be monitored at least alternate years in patients who stop taking oral bisphosphonates; those with a rapid decline in BMD of >10% in two years or >5% from baseline should be switched to alternate treatment or resume bisphosphonate therapy (Colon-Emeric 2006).