I have been considering bisphosphonates for two reasons. First, and most salient, I intend to go on low dose (7.5mg/day) pioglitazone, and pio can cause fractures because it inhibits osteoblasts without inhibiting osteoclasts. Second, well, it appears there may be some pleiotropic benefit vs health/longevity (highly speculative and context dependent).
At the same time, bisphosphonates are very tricky drugs with great downside potential. Even in my pio scenario, all they do is inhibit osteoclasts without activating osteoblasts. This means you might get better bone density, but not bone strength/health.
Researching the topic, I have reached a few conclusions. Of the readily available (non-IV) bisphosphonates, risedronate (Actonel) appears the best of the bunch.
Best to take it once a week 35mg at a time. Careful how you take it. Empty stomach. Enough time to pass through (90 minutes) - sitting up or standing, i.e. don’t lie down or it’ll burn your esophagus.
Best to take for a limited period of time, unless there are strong reasons to persist. If you are a younger person (under 70), I would consider 3-6 months or up to 1 year, not more. During that time, do NOT plan on any dental surgeries, implants or extractions. Give it at least a 6 month margin on both sides, so if you take Actonel for 1 year, effectively, 6 months before, 1 year during and 6 months after, do not plan on such dental procedures, i.e. 2 years.
Once you’ve built up bone density with Actonel, give it a break and only revisit if you get osteopenic again, at which point, you may repeat the 3-6 mo - 1 year course of Actonel.