Drug Interactions and Osteoporosis
Drugs which may affect metabolism of calcium and vitamin D:
- Thiazides decrease urinary calcium loss and are sometimes prescribed for patients with elevated 24 hour urinary calcium excretion. Hypercalcaemia and possibly metabolic alkalosis (milk-alkali syndrome) can develop in patients given high dose vitamin D and/or large amounts of calcium if they are additionally treated with diuretics such as thiazides.
- Long term phenytoin and anti-convulsant medications may interfere with vitamin D and calcium metabolism which therefore may increase the risk of osteoporosis. Monitor concurrent treatment. An increase in vitamin D supplements may be required.
- Calcium impedes absorption of a number of medications including atenolol, salicylates, iron, tetracycline, quinolones, and bisphosphonates. Calcium can also limit progesterone absorption. It is advised to space by 2 hours.
- Cholestyramine may decrease intestinal absorption of Vitamin D analogues.
Topic Code: 5070