Paricalcitol

Paricalcitol (chemically it is 19-nor-1,25-(OH)2-vitamin D2. Marketed by Abbott Laboratories under the trade name Zemplar) is a drug used for the prevention and treatment of secondary hyperparathyroidism (excessive secretion of parathyroid hormone) associated with chronic kidney failure. It is an analog of 1,25-dihydroxyergocalciferol, the active form of vitamin D2 (ergocalciferol).

Paricalcitol
Clinical data
Trade namesZemplar
Other names(1R,3S)-5-[2-[(1R,3aR,7aS)-1-[(2R,5S)-6-hydroxy-5,6-dimethyl-3E-hepten-2-yl]-7a-methyl-2,3,3a,5,6,7-hexahydro-1H-inden-4-ylidene]ethylidene]-cyclohexane-1,3-diol
AHFS/Drugs.comMonograph
MedlinePlusa682335
Pregnancy
category
  • AU: C
  • US: C (Risk not ruled out)
    Routes of
    administration    		Oral, Intravenous
    ATC code
    Legal status
    Legal status
    Pharmacokinetic data
    Bioavailability72%[1]
    Protein binding99.8%[1]
    MetabolismHepatic[1]
    Elimination half-life14-20 hours[1]
    ExcretionFaeces (74%), urine (16%)[1]
    Identifiers
    CAS Number
    PubChem CID
    IUPHAR/BPS
    DrugBank
    ChemSpider
    UNII
    KEGG
    ChEBI
    ChEMBL
    CompTox Dashboard (EPA)
    ECHA InfoCard100.184.862
    Chemical and physical data
    FormulaC27H44O3
    Molar mass416.646 g·mol−1
     NY (what is this?)  (verify)

    It was patented in 1989 and approved for medical use in 1998.[2]

    Medical uses

    Its primary use in medicine is in the treatment of secondary hyperparathyroidism associated with chronic kidney disease.[3] However current evidence is not sufficient to demonstrate an advantage of paricalcitol over non-selective vitamin D derivatives for this indication.[4]

    Adverse effects

    Adverse effects by frequency:[1][3][5][6]
    Very common (>10% frequency):

    • Nausea

    Common (1-10% frequency):

    Uncommon (0.1-1% frequency):

    ‡ These are adverse effects only seen in patients with grade 3 or 4 chronic kidney disease. † These are adverse effects only seen in patients with grade 5 chronic kidney disease.

    Contraindications

    Contraindications include:[6]

    whereas cautions include:[1]

    • Impaired liver function
    • It is also advised that physicians regularly monitor their patients' calcium and phosphorus levels.

    Interactions

    Drugs that may interact with paricalcitol include:[1][6]

    • Ketoconazole, as it may interfere with paricalcitol's metabolism in the liver.
    • Digitoxin, hypercalcaemia due to any cause can exacerbate the toxicity of digitoxin.
    • Thiazide diuretics or calcium supplements as hypercalcaemia may be induced by this combination
    • Magnesium-containing products such as antacids may increase the risk of hypermagnesemia.
    • Aluminium-containing products such as antacids may increase the risk of aluminium toxicity.
    • Drugs that interfere with the absorption of fat-soluble vitamins, such as cholestyramine may interfere with the absorption of paricalcitol.

    Overdose

    Electrolyte abnormalities (e.g. hypercalcaemia and hyperphosphataemia) are common overdose symptoms.[6] Treatment is mostly supportive, with particular attention being paid to correcting electrolyte anomalies and reducing intake of calcium in both the form of supplementation and diet.[6] As it is so heavily bound to plasma proteins haemodialysis is unlikely to be helpful in cases of overdose.[6]

    Early symptoms of overdose can include:[6]

    • Weakness
    • Headache
    • Somnolence
    • Nausea
    • Vomiting
    • Dry mouth
    • Constipation
    • Muscle pain
    • Bone pain
    • Metallic taste in the mouth.

    It is worth noting, however, that may of these symptoms are also indicative of kidney failure and hence may be masked by the patient's condition.[6]

    Late symptoms of overdose include:

    • Loss of appetite
    • Weight loss
    • Conjunctivitis (calcific)
    • Pancreatitis
    • Photophobia
    • Rhinorrhoea
    • Pruritus
    • Hyperthermia
    • Decreased libido
    • Elevated BUN
    • Hypercholesterolaemia
    • Elevated AST and ALT
    • Ectopic calcification
    • Hypertension
    • Cardiac arrhythmias
    • Somnolence
    • Death
    • Psychosis (rare)

    Mechanism of action
    3D structure of paricalcitol

    Like 1,25-dihydroxyergocalciferol, paricalcitol acts as an agonist at the vitamin D receptor and thereby lowers parathyroid hormone levels in the blood.[1]

    Pharmacokinetics

    The plasma concentration of paricalcitol decreases rapidly and log-linearly within two hours after initial intravenous administration. Therefore, it is not expected to accumulate with multiple dosing, since paricalcitol is usually given no more frequently than every other day (3 times per week).[7][8]

    References
    1. "Zemplar (paricalcitol) dosing, indications, interactions, adverse effects, and more". Medscape Reference. WebMD. Retrieved 26 January 2014.
    2. Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 452. ISBN 9783527607495.
    3. Rossi S, ed. (2013). Australian Medicines Handbook (2013 ed.). Adelaide: The Australian Medicines Handbook Unit Trust. ISBN 978-0-9805790-9-3.
    4. Cai P, Tang X, Qin W, Ji L, Li Z (April 2016). "Comparison between paricalcitol and active non-selective vitamin D receptor activator for secondary hyperparathyroidism in chronic kidney disease: a systematic review and meta-analysis of randomized controlled trials". International Urology and Nephrology. 48 (4): 571–84. doi:10.1007/s11255-015-1195-6. PMID 26748501.
    5. "PARICALCITOL capsule, liquid filled [Teva Pharmaceuticals USA Inc]" (PDF). DailyMed. Teva Pharmaceuticals USA Inc. September 2013. Retrieved 26 January 2014.
    6. "Zemplar Soft Capsules 1 mcg - Summary of Product Characteristics". electronic Medicines Compendium. AbbVie Limited. 15 April 2013. Retrieved 26 January 2014.
    7. Rxlist: Zemplar
    8. "Zemplar (paricalcitol) [prescribing information]". North Chicago, IL: AbbVie Inc. October 1, 2015. Retrieved December 12, 2016.
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