Mechanism of action

Bisphosphonates are analogues of pyrophosphate, a molecule which decreases demineralisation in bone.

Indications

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

Monitoring

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'

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