Short answer: Both are once-weekly bisphosphonate tablets for osteoporosis.12 Atelvia is risedronate 35 mg delayed-release, taken right after breakfast. Fosamax is alendronate 70 mg, taken on an empty stomach at least 30 minutes before food, drink or other medicine. Fosamax has more approved uses. Neither label compares them, and neither has a boxed warning.
| Atelvia | Fosamax | |
|---|---|---|
| Drug | Risedronate sodium 35 mg, delayed-release1 | Alendronate sodium 70 mg2 |
| Food | Immediately following breakfast1 | On getting up, at least 30 minutes before food, drink or other medicine2 |
| Water | At least 4 ounces1 | 6 to 8 ounces of plain water2 |
| Approved for | Treating postmenopausal osteoporosis1 | Treating and preventing postmenopausal osteoporosis, men, steroid-induced osteoporosis, Paget's disease2 |
| Label comparator | Daily immediate-release risedronate 5 mg1 | Placebo, and 70 mg weekly vs 10 mg daily2 |
| Stomach side effects | Diarrhea 8.8%, abdominal pain 5.2%1 | Abdominal pain 3.7% on 70 mg weekly (drug-related)2 |
| Kidney limit | Not recommended under 30 mL/min1 | Not recommended under 35 mL/min2 |
| Missed weekly dose | Take it the morning after you remember; never 2 on one day1 | Take it the morning after you remember; never 2 on one day2 |
| Boxed warning | None1 | None2 |
The Atelvia label's 1-year trial compared it with daily immediate-release risedronate 5 mg: spine bone density rose 3.3% vs 3.1%, with diarrhea 8.8% vs 4.9%. The Fosamax label compared 70 mg weekly with 10 mg daily for 1 year, with similar overall safety and abdominal pain judged drug-related in 3.7% vs 3.0%.12 The two tables count reactions differently: Atelvia's lists all reactions, Fosamax's only those the investigators judged drug-related. These numbers come from separate trials with different people, lengths and methods, so they are not a head-to-head comparison.
Both are swallowed whole while upright, and the person stays upright for 30 minutes. Both share warnings on the esophagus, low calcium, jaw bone problems, severe bone, joint or muscle pain and unusual thigh fractures. Both labels say the best length of use has not been set and people at low fracture risk may be considered for stopping after 3 to 5 years.12
Which, if either, fits is for your prescriber. More detail: Atelvia side effects, Fosamax side effects, the Atelvia and Fosamax dosing schedules, the Fosamax missed-dose page, how to store Fosamax and Fosamax vs Actonel: how do alendronate and risedronate differ?.