1. Clinical Overview
Risedronate sodium is a pyridinyl bisphosphonate that acts as a potent antiresorptive agent. It is a third-generation nitrogen-containing bisphosphonate specifically indicated for the treatment and prevention of osteoporosis in postmenopausal women and glucocorticoid-induced osteoporosis. It inhibits osteoclast-mediated bone resorption, leading to a net increase in bone mineral density (BMD) and a reduction in fracture risk. The 35mg dose is formulated as a delayed-release tablet for once-weekly oral administration, designed to improve upper GI tolerability.
| Onset | Duration | Bioavailability |
|---|---|---|
| Biochemical markers of bone resorption (e.g., urinary N-telopeptide) decrease significantly within 1 month of therapy. | The skeletal effects are prolonged due to binding to bone mineral. Pharmacological action persists for weeks after a single dose, but weekly dosing is required to maintain continuous suppression of bone turnover. | Approximately 0.63% for the immediate-release tablet under fasting conditions. The bioavailability of the delayed-release 35mg tablet is similar when taken as directed (after breakfast). |
2. Mechanism of Action
Risedronate has a high affinity for hydroxyapatite crystals in bone. It is selectively taken up by and adsorbed to the bone surface at sites of active bone resorption. It is internalized by osteoclasts during the resorption process. Inside the osteoclast, it inhibits the enzyme farnesyl pyrophosphate synthase (FPPS) in the mevalonate pathway.
3. Indications & Uses
- Treatment of Postmenopausal Osteoporosis (to increase bone mass and reduce the risk of vertebral and hip fractures)
- Prevention of Postmenopausal Osteoporosis
- Treatment and prevention of Glucocorticoid-Induced Osteoporosis (in men and women)
4. Dosage & Administration
Adult Dosage: For Postmenopausal Osteoporosis (Treatment & Prevention) & Glucocorticoid-Induced Osteoporosis: One 35mg delayed-release tablet orally, once a week.
Administration: DELAYED-RELEASE 35mg TABLET: Must be taken in the morning immediately after breakfast. Swallow the tablet whole with a full glass of plain water (at least 120 ml). Do NOT crush, chew, or suck the tablet. Do NOT take while lying down or reclining. After taking the tablet, remain upright (sitting, standing, or walking) for at least 30 minutes. Do NOT eat or drink anything other than plain water for at least 30 minutes after taking the tablet. Do NOT take at bedtime or before rising for the day.
5. Side Effects
Common side effects may include:
- Dyspepsia
- Abdominal pain
- Nausea
- Diarrhea
- Constipation
- Headache
- Musculoskeletal pain (bone, joint, muscle)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Calcium Supplements / Antacids (containing Ca, Mg, Al, Fe) | Severely impair absorption of risedronate. | Major. Administer at a different time of day (at least 2-4 hours apart). |
| NSAIDs (e.g., Ibuprofen, Diclofenac) | May increase risk of gastrointestinal irritation and ulceration. | Moderate. Use with caution. |
| Aminoglycosides (e.g., Gentamicin) | May have additive hypocalcemic effect. | Moderate. Monitor serum calcium. |
| Loop Diuretics (e.g., Furosemide) | May increase risk of hypocalcemia. | Moderate. |
| PPIs (e.g., Omeprazole) | Theoretically may reduce efficacy of delayed-release risedronate (which requires an acidic environment for release). However, clinical significance is debated. Immediate-release risedronate absorption is not affected. | Moderate. Consider monitoring BMD response. |
7. Patient Counselling
- DO take the 35mg delayed-release tablet immediately AFTER breakfast, with a full glass of plain water.
- DO remain upright (sitting, standing, walking) for at least 30 minutes after taking the tablet.
- DO take calcium and vitamin D supplements as prescribed by your doctor, but at a different time of day (e.g., afternoon or evening).
- DO inform all your healthcare providers (dentist, surgeon) that you are taking this medicine before any invasive dental or surgical procedures.
- DO NOT crush, chew, or suck the tablet.
- DO NOT take the tablet while lying down or at bedtime.
- DO NOT eat or drink anything other than plain water for at least 30 minutes after taking the tablet.
8. Toxicology & Storage
Overdose: Hypocalcemia, hypophosphatemia, and upper gastrointestinal adverse events such as upset stomach, heartburn, esophagitis, gastritis, or ulcer. No specific organ toxicity from single overdose reported.
Storage: Store at room temperature (15°C to 30°C). Protect from moisture. Keep in the original blister pack until use. Keep out of reach of children.