Therapeutic targets
Therapy recommendations
- For tetany (to stop muscle spasms): 20 ml calcium gluconate solution 10% (slow i.v. injection).
- Caveat:
- If the patient is taking digitalis (antiarrhythmic drug), do not administer calcium i.v., because calcium and digitalis act synergistically!
- If the etiology (cause) of tetany is unclear, serum calcium and phosphate levels should be determined before calcium administration.
- Caveat:
- Long-term treatment: substitution of calcium and vitamin D (vitamin D derivatives), which also normalizes the elevated serum phosphate level.
- Normally, activation of calcitriol in the kidney is regulated by parathyroid hormone (PTH). Thus, in PTH deficiency, the active form of vitamin D, i.e., calcitriol (doubly hydroxylated vitamin D3), must be administered:
- Calcitriol (1,25-(OH)2-vitamin D3): 0.25-1 µg/d (20-40 ng/kg bw/day) – alternatively, alfacalcidol drops (50 ng/kg bw/day) – plus calcium orally 0.5-1.5 g/d (20-30 mg/kg bw/day; max. 1,500 mg).
- Note: Monitor serum calcium and urinary calcium excretion to avoid hypercalcemic syndrome or crisis.
- Target range: serum calcium should be maintained in the lower normal range.
- Monitor serum phosphate – if necessary, bring phosphate binders to use if serum phosphate does not fall during therapy.
- To prevent deposition of calcium phosphate crystals in the vascular system and the formation of kidney stones, the calcium phosphate product should be <4.
- Normally, activation of calcitriol in the kidney is regulated by parathyroid hormone (PTH). Thus, in PTH deficiency, the active form of vitamin D, i.e., calcitriol (doubly hydroxylated vitamin D3), must be administered:
Other notes
- If parathyroid hormone is deficient, the disorder can also be treated by “off-label use” of teriparatide, consisting of the first 34 amino acids of parathyroid hormone. A complete recombinant version of parathyroid hormone (rhPTH) is now available. In a Phase III study, it was shown that in 54.8% of patients, the administration of rhPTH (versus 2.5% in the placebo group) reduced the daily dose of calcium and vitamin D by 50%, without a drop in serum calcium.
