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calcitriol; 1,25-dihydroxycholcalciferol; 1,25-dihydroxyvitamin D3

Tradename: Rocaltrol. Indications: 1) management of metabolic bone disease & hypocalcemia in patients with renal failure 2) vitamin D deficiency 3) hypocalcemic tetany 4) hypoparathyroidism 5) hypophosphatemia [6] 6) treatment of multiple sclerosis? [5] Dosage: 1) 0.25 ug PO QD (initially) 2) 0.5-2.0 ug PO QD (maintenance) 3) dose may be increased at 2-4 week intervals 4) post-parathyroidectomy: [4] a) up to 4 ug/day b) IV administration is an option 0.25, 0.5 ug capsules. Pharmacokinetics: 1) maximal hypercalcemic effects occur in about 4 weeks after daily administration of a fixed dose 2) 1/2life is 3-2 hours Adverse effects: 1) not common (1-10%) - hypotension, cardiac arrhythmias, irritability*, headache, nausea/vomiting, bone pain, hypertension, pruritus, anorexia, pancreatitis, muscle pain, conjunctivitis, photophobia, polyuria*, polydypsia*, metallic taste 2) uncommon (< 1%) - weight loss*, overt psychosis 3) other [1] a) hypercalcemia: - generally resolves within 1 week - monitor serum Ca+2 every 24-48 hours b) weakness c) headache d) somnolence e) dry mouth f) constipation g) suppression of autotransplanted parathyroid tissue after parathyroidectomy (high dose) * late effects [1] Drug interactions: 1) antacids: hypermagnesemia may result in patients with renal failure 2) cholestyramine & colestipol may decrease effect of calcifetriol 3) phenobarbital, phenytoin & rifampin inhibit conversion of 25-hydroxyvitamin D into calcitriol [3] Mechanism of action: 1) active form of vitamin D, also see vitamin D 2) calcitriol stimulates intestinal Ca+2 & phosphate transport Biochemistry: 1) vitamin D3 is hydroxylated in the liver to form 25-OH vit D3 2) 25-OH vitamin D3 is hydroxylated in the kidney to form 1,25- dihydroxy vitamin D3 (calcitriol), the active metabolite of vitamin D3 by 5-hydroxyvitamin D-1 alpha hydroxylase (CYP27B1) Pathology: - CYP27B1 is also present in macrophages & may be stimulated to produce calcitriol in granulomatous disease, resulting in hypercalcemia [3]

Interactions

drug interactions

Related

1,25-dihydroxyvitamin D3 in serum (serum calcitriol) vitamin D3 receptor; VDR; 1,25-dihydroxyvitamin D3 receptor; nuclear receptor subfamily 1 group I member 1 (VDR, NR1I1)

Specific

calcitriol topical (Vectical)

General

cholecalciferol; vitamin D3

Properties

MISC-INFO: elimination route LIVER 1/2life 3-6 HOURS pregnancy-category C safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  2. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 16. American College of Physicians, Philadelphia 1998, 2012
  4. UpToDate 11.2 2003
  5. Wingerchuk DM, Lesaux J, Rice GP, Kremenchutzky M, Ebers GC. A pilot study of oral calcitriol (1,25-dihydroxyvitamin D3) for relapsing-remitting multiple sclerosis. J Neurol Neurosurg Psychiatry. 2005 Sep;76(9):1294-6. PMID: 16107372
  6. Deprecated Reference

Component-of

calcitriol/fluticasone/tacrolimus