calcitriol; 1,25-dihydroxycholcalciferol; 1,25-dihydroxyvitamin D3
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Introduction
Tradename: Rocaltrol.
Pathology
- CYP27B1 is also present in macrophages & may be stimulated to produce calcitriol in granulomatous disease, resulting in hypercalcemia[3]
Biochemistry
- vitamin D3 is hydroxylated in the liver to form 25-OH vit D3
- 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)
Indications
- management of metabolic bone disease & hypocalcemia in patients with renal failure
- vitamin D deficiency
- hypocalcemic tetany
- hypoparathyroidism
- hypophosphatemia[6]
- treatment of multiple sclerosis?[5]
Dosage
- 0.25 ug PO QD (initially)
- 0.5-2.0 ug PO QD (maintenance)
- dose may be increased at 2-4 week intervals
- post-parathyroidectomy:[4]
- up to 4 ug/day
- IV administration is an option
0.25, 0.5 ug capsules.
Pharmacokinetics
- maximal hypercalcemic effects occur in about 4 weeks after daily administration of a fixed dose
- 1/2life is 3-2 hours
elimination via liver
1/2life = 3-6 hours
Adverse effects
- not common (1-10%)
- uncommon (< 1%)
- weight loss*, overt psychosis
- other[1]
- hypercalcemia:
- generally resolves within 1 week
- monitor serum Ca+2 every 24-48 hours
- weakness
- headache
- somnolence
- dry mouth
- constipation
- suppression of autotransplanted parathyroid tissue after parathyroidectomy (high dose)
- hypercalcemia:
Drug interactions
- antacids: hypermagnesemia may result in patients with renal failure
- cholestyramine & colestipol may decrease effect of calcifetriol
- phenobarbital, phenytoin & rifampin inhibit conversion of 25-hydroxyvitamin D into calcitriol[3]
Mechanism of action
- active form of vitamin D, also see vitamin D
- calcitriol stimulates intestinal Ca+2 & phosphate transport
More general terms
More specific terms
Additional terms
- 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)
References
- ↑ 1.0 1.1 1.2 Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ 3.0 3.1 3.2 Medical Knowledge Self Assessment Program (MKSAP) 11, 16. American College of Physicians, Philadelphia 1998, 2012
- ↑ 4.0 4.1 UpToDate 11.2 2003
- ↑ 5.0 5.1 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: https://www.ncbi.nlm.nih.gov/pubmed/16107372
- ↑ 6.0 6.1 Deprecated Reference
Database
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=134070
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=104991
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5280453
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5280447
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=36083
- PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=2524