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Bisphosphonates

Bisphosphonates are analogues of pyrophosphate, a molecule which decreases demineralisation in bone. They inhibit osteoclasts by reducing recruitment and promoting apoptosis.

Clinical uses

  • prevention and treatment of osteoporosis
  • hypercalcaemia
  • Paget's disease
  • pain from bone metatases

Adverse effects

  • oesophageal reactions: oesophagitis, oesophageal ulcers (especially alendronate)
  • osteonecrosis of the jaw
  • increased risk of atypical stress fractures of the proximal femoral shaft in patients taking alendronate
  • acute phase response: fever, myalgia and arthralgia may occur following administration
  • hypocalcaemia: due to reduced calcium efflux from bone. Usually clinically unimportant

The BNF suggests the following counselling for patients taking oral bisphosphonates

  • 'Tablets should be swallowed whole with plenty of water while sitting or standing; to be given on an empty stomach at least 30 minutes before breakfast (or another oral medication); patient should stand or sit upright for at least 30 minutes after taking tablet'

Hypocalcemia/vitamin D deficiency should be corrected before giving bisphosphonates. However, when starting bisphosphonate treatment for osteoporosis, calcium should only be prescribed if dietary intake is inadequate. Vitamin D supplements are normally given.

The duration of bisphosphonate treatment varies according to the level of risk. Some authorities recommend stopping bisphosphonates at 5 years if the following apply:
- patient is < 75-years-old - femoral neck T-score of > -2.5 - low risk according to FRAX/NOGG

Questions

  1. A 72-year-old female known to have osteoporosis is started on alendronate. Which one of the following side-effects is it most important to warn her about?