Objective: To examine in a major cohort of patients whether or not musculoskeletal adverse effects (MAEs), similar to those seen in intravenous bisphosphonates (BP), might occur also in high dosage oral treatment regimens with alendronate (ALN) and risedronate (RSN).
Patients and methods: 612 consecutive patients treated in the osteoporosis outpatient clinic at Charite, Campus Benjamin Franklin, between July 2002 and October 2003 with oral ALN or RSN (mean age 68.2+/-9.7 years; 527 females, 85 males), were examined and followed up for MAEs.
Results: The overall frequency of any severe MAEs in our patients was low (5.6%). All severe MAEs occurred in primarily once weekly treated patients: 27 in ALN 70 mg once weekly (27/134=20.1%) and 7 in RSN 35 mg once weekly (7/28=25.0%), with no significant difference between those groups. The most frequently reported MAE was acute arthralgia in 12.6%, followed by acute back pain in 9.1% of all primarily once weekly treated cases. None of the 302 patients initially treated with daily BP reported any MAEs when later switching to once weekly administration (218 patients to ALN 70 mg once weekly and 84 patients to RSN 35 mg once weekly). With reference to recently published data, the phenomenon is probably related to dose dependent gammadelta T cell activation by accumulation of isopentenyl pyrophosphate (IPP) due to inhibition of the mevalonate pathway by nitrogen containing bisphosphonates (nBP).
Conclusions: MAEs in oral BP are, in general, less common and severe than in intravenous BP. They are observed exclusively in patients starting ALN or RSN treatment with once weekly dosage regimens. In order to avoid this phenomenon, it is suggested to start ALN or RSN treatment with the lower daily dosages of ALN 10 mg daily or RSN 5 mg daily for about two weeks before switching to the overall, more convenient, once weekly dose regimen.