Calcium and Vitamin D

Question 1

Indications

Answer 1

1. Used in osteoporosis to ensure positive calcium balance when dietary intake and/or sunlight exposure are insufficient
2. Used in CKD to treat and prevent secondary hyperparathyroidism and renal osteodystrophy
3. Used in severe hyperkalaemia to prevent life-threatening arrhythmias
4. Used in hypocalcaemia that is symptomatic
5. Used in prevention and treatment of vit D deficiency

Question 2

Mechanism of action

Answer 2

Calcium is essential for normal function.

Ca homeostasis is controlled by parathyroid hormone and vit D, which increase Ca levels and bone mineralisation, and calcitonin which reduces the serum Ca levels.

In osteoporosis there is a loss of bone mass which increases the risk of fracture.
Restoring a positive calcium balance can slow the bone loss.

In severe chronic kidney disease impaired phosphate excretion and reduced activation of vitamin D cause hyperphosphataemia and hypocalceamia. This stimulates secondary hyperparathyroidism, which leads to renal osteodystrophy.

In hyperkalaemia calcium raises the myocardial threshold potential reducing excitability.

Question 3

Adverse effects

Answer 3

Dyspepsia

Question 4

Interactions

Answer 4

Oral calcium reduces the absorption of many drugs eg iron, bisphosphonates, tetracyclines, levothyroxine

Question 5

Prescribing

Answer 5

Osteoporosis - aim to supplement dietary intake

Severe hyperkaleamia - 10ml of calcium gluconate 10% by slow IV injection. Repeat of ECG changes persist.

Seek guidance for use in severe/symptomatic hypocalcaemia and severe CKD

Question 6

Administration

Answer 6

Oral preparations are usually chewed

Question 7

Communication

Answer 7

Depends on indication

Question 8

Monitoring

Answer 8

Patients with severe hyperkalaemia require continuous cardiac monitoring. You should repeat a 12-lead ECG after administration of calcium to confirm treatment success.

Any patient receiving calcium supplementation should have their levels monitored.