Strontium 💊

Related Subjects: | Osteoporosis

⚠️ Important: Use strontium ranelate only under specialist supervision. There are significant cardiovascular and thrombotic risks - prescribe only when other osteoporosis treatments (e.g. bisphosphonates, denosumab, teriparatide) are contraindicated or not tolerated.

🧠 About

• Strontium ranelate is a unique agent with dual action on bone: it both increases bone formation and decreases bone resorption.
• Its use in the UK is now highly restricted following MHRA and EMA safety warnings (2013–2014) due to increased cardiovascular risk.
• Therapy should be initiated only by a physician experienced in managing osteoporosis and with regular review of cardiovascular status (every 6–12 months).
• Should be used as part of a comprehensive plan that includes lifestyle measures, calcium, and vitamin D supplementation.

⚙️ Mode of Action

• Strontium (atomic number 38) is chemically similar to calcium and can be incorporated into the bone matrix.
• Stimulates osteoblast replication and collagen synthesis while simultaneously reducing osteoclast differentiation and activity.
• This “rebalancing” effect leads to an increase in bone formation markers and bone mineral density.
• Unlike bisphosphonates, it does not inhibit the mevalonate pathway; instead, it exerts effects via calcium-sensing receptors and osteoprotegerin modulation.

🎯 Indications

• Treatment of severe postmenopausal osteoporosis in women and osteoporosis in men at high risk of fracture - only when other approved treatments are unsuitable.
• Prescribers must:
  • Assess cardiovascular risk before starting.
  • Monitor blood pressure and cardiovascular health every 6–12 months.
  • Discontinue immediately if the patient develops ischaemic heart disease, peripheral arterial disease, cerebrovascular disease, or uncontrolled hypertension.

💊 Dose

⚠️ Administration Advice

• Take at bedtime, preferably at least 2 hours after food or milk.
• Food, milk, and calcium supplements markedly reduce absorption - separate dosing by ≥2 hours.
• Do not take with aluminium or magnesium antacids; if needed, wait 2 hours after taking strontium.
• Ensure adequate vitamin D and calcium intake during treatment.

🚫 Contraindications

• Current or previous venous thromboembolism (VTE) - including DVT or pulmonary embolism.
• History of ischaemic heart disease, peripheral arterial disease, or cerebrovascular disease.
• Uncontrolled hypertension.
• Temporary or permanent immobilisation (e.g. post-surgery, prolonged bed rest).
• Hypersensitivity to strontium or excipients.

⚠️ Cautions

• Perform a baseline cardiovascular assessment before treatment.
• Reassess benefit–risk balance at each follow-up visit.
• Advise patient to report chest pain, dyspnoea, or leg swelling immediately (possible VTE or cardiac event).
• Use caution in renal impairment; avoid if eGFR < 30 mL/min.
• Monitor for dermatological reactions such as rash or eczema.

💥 Side Effects

• Common: Nausea, diarrhoea, headache, dermatitis, eczema, peripheral oedema.
• Cardiovascular: Increased risk of venous thromboembolism and myocardial infarction.
• Allergic reactions: DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) - rare but potentially life-threatening.
• Gastrointestinal: Reflux, abdominal pain, dyspepsia, vomiting, flatulence, constipation, stomatitis.
• Haematological: Rare bone marrow suppression or cytopenias.

💡 Teaching Tip

• Strontium ranelate represents a “dual-action bone agent” - both anabolic and antiresorptive - but its clinical value is now overshadowed by safety concerns.
• Explain to learners that while it increases BMD, strontium atoms are heavier than calcium, potentially artificially inflating DEXA readings.
• Mnemonic: “STRONG but STRONtium risks” - effective for bones, risky for the heart.

📚 References

• BNF: Strontium Ranelate
• MHRA Drug Safety Update (2014): Cardiovascular risk with strontium ranelate (Protelos/Osseor)
• European Medicines Agency: PRAC recommendations, 2014
• NICE NG226: Osteoporosis: assessment and management (2023)