Ostoris (Risedronate Sodium)

Ostoris is a bisphosphonate indicated for disorders that affect bone remodeling and density.

• Post‑menopausal osteoporosis: reduces risk of vertebral and hip fractures.
• Male osteoporosis: improves bone mineral density and lowers fracture incidence.
• Glucocorticoid‑induced osteoporosis: mitigates bone loss associated with long‑term steroid therapy.
• Paget’s disease of bone: normalises abnormal bone turnover.

• Risedronate sodium binds to hydroxy‑apatite crystals in bone, where it is taken up by osteoclasts during resorption. The drug inhibits farnesyl pyrophosphate synthase, a key enzyme in the mevalonate pathway, leading to reduced osteoclast activity, impaired bone resorption and a net increase in bone mineral density.

Adverse reactions to risedronate sodium are generally dose‑related and may vary in frequency.

Common Side Effects

• Upper gastrointestinal irritation, including dyspepsia and heartburn.
• Nausea or vomiting.
• Musculoskeletal pain, especially in the back, hips or thighs.
• Transient flu‑like symptoms after the first dose.
• Headache.

Serious or Rare Side Effects

• Osteonecrosis of the jaw (ONJ).
• Atypical femoral fractures.
• Severe esophagitis or esophageal ulceration.
• Acute phase reactions with fever and myalgia.
• Hypocalcaemia, especially in patients with vitamin D deficiency.

Before prescribing risedronate sodium, clinicians should assess individual risk factors and ensure appropriate monitoring.

• Renal function: evaluate creatinine clearance before initiation and periodically thereafter.
• Calcium and vitamin D status: correct deficiencies prior to therapy.
• Gastro‑intestinal health: avoid in patients with active esophageal disorders.
• Concomitant medications: review for agents that may impair absorption (e.g., calcium supplements, antacids).
• Pregnancy and lactation: contraindicated; avoid use in women who are pregnant or breastfeeding.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Risedronate sodium may interact with several medicines, altering its absorption or increasing the risk of adverse events.

Major Interactions (Avoid)

• Calcium carbonate or calcium citrate supplements taken within 30 minutes of the dose.
• Antacids containing aluminum, magnesium or sodium.
• Oral bisphosphonates taken concurrently.

Moderate Interactions (Monitor Closely)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs) that may increase gastrointestinal irritation.
• Corticosteroids, which can compound bone‑loss risk.
• Proton‑pump inhibitors that may affect esophageal healing.
• Vitamin D analogues, requiring dose adjustments based on serum levels.
• Diuretics that may predispose to hypocalcaemia.