Bisphosphonates

Question 1

What are examples of generic and brand names of bisphosphonates?

Answer 1

• Alendronic acid (Fosamax)
• Risedronate (Actonel)
• Pamidronate
• Zoledronic acid

Question 2

What is the method of action of bisphosphonates?

Answer 2

• Similar structure to naturally occurring pyrophosphate – readily incorporated into the bone
• Inhibit the action of osteoclasts which are cells responsible for bone resorption
• Also promotes apoptosis of the osteoclasts
• = ↓ in bone loss and improvement in bone mass

Question 3

What are the indications for bisphosphonates?

Answer 3

• Osteoporotic fragility fractures – Alendronic acid is 1st line
• Severe hypercalcaemia of malignancy – Pamidronate and zoledronic acid are used
• For patients with myeloma and breast cancer with bone metastases, bisphosphonates reduce the risk of pathological fractures, cord compression and need for radiotherapy/surgery
• Metabolically active Paget’s disease – reduces bone turnover and pain

Question 4

What are the contraindications for bisphosphonates?

Answer 4

• Severe renal impairment
• Hypocalcaemia
• Active upper GI disorder – oral administration contraindicated
• Smokers – due to risk of osteonecrosis
• Dental disease – due to risk of osteonecrosis

Question 5

What are the side effects of bisphosphonates?

Answer 5

• Oesophagitis
• Hypophosphataemia
• Osteonecrosis of the jaw – rare but serious, more likely with IV
• Atypical femoral fracture – rare but serious, more common on long term treatment

Question 6

What are the interactions with bisphosphonates?

Answer 6

• Calcium salt containing products e.g. antacids – due to binding to Ca so absorption is ↓
• Iron salts

Question 7

What organ eliminates bisphosphonates?

Answer 7

Kidney

Question 8

What information should be given to patients taking bisphosphonates?

Answer 8

• Should be swallowed whole at least 30 mins before breakfast/other medication
• Take with plenty of water
• Remain upright for 30 mins after taking to reduce oesophageal irritation