Short answer: Both are bisphosphonates for osteoporosis and Paget's disease. Reclast (zoledronic acid) is a 5 mg infusion into a vein, once a year for treatment.1 Actonel (risedronate) is a tablet taken daily, weekly or monthly on an empty stomach, staying upright for 30 minutes.2 In Paget's disease, the Reclast label reports 6-month trials against oral risedronate: 96% vs 74% responded.1
| Reclast | Actonel | |
|---|---|---|
| How given | 5 mg infusion into a vein over at least 15 minutes1 | Tablet with 6 to 8 ounces of plain water, 30 minutes before food, upright for 30 minutes2 |
| Postmenopausal osteoporosis | Once a year to treat; once every 2 years to prevent1 | 5 mg daily, 35 mg weekly, 75 mg on two days a month, or 150 mg monthly2 |
| Paget's disease | One infusion1 | 30 mg daily for 2 months2 |
| Paget's trials, 6 months | Response 96% on Reclast vs 74% on risedronate 30 mg daily for 2 months1 | Not in the Actonel label2 |
| Kidney limit | Not given below a creatinine clearance of 35 mL/min1 | Not recommended below 30 mL/min2 |
| Osteoporosis trial side effects | Fever 17.9% vs 4.6% on placebo; muscle pain 11.7% vs 3.7%1 | Back pain 28.0% vs 26.1% on placebo; abdominal pain 12.2% vs 9.9%2 |
| Boxed warning | None1 | None2 |
The Reclast label reports two identical 6-month, double-blind trials in 349 people with Paget's disease of bone: one 5 mg Reclast infusion vs oral risedronate 30 mg daily for 2 months. At 6 months, 96% on Reclast had a treatment response vs 74% on risedronate, and alkaline phosphatase was back to normal in 89% vs 58%. Flu-like acute phase symptoms were 25% vs 8%.1 The trials used risedronate, the drug in Actonel, and covered Paget's disease only, not osteoporosis.
For osteoporosis, each label compares its drug with placebo, so the side-effect rows above come from separate trials and are not a head-to-head comparison. Reclast's fever and aches mostly start within 3 days of the infusion; acetaminophen afterward may help.1 Actonel can irritate the esophagus, so it is stopped for pain or trouble swallowing or new heartburn.2 Both warn of low calcium, jaw bone death and unusual thigh fractures, and both labels say people at low fracture risk may stop after 3 to 5 years.12
Which, if either, fits is for your prescriber. More detail: Reclast side effects, Actonel side effects, the Reclast and Actonel dosing schedules, the Reclast and Actonel missed-dose pages, the zoledronic acid and risedronate guides, and Reclast vs Fosamax: how do the two bisphosphonates differ?.