Calcitriol

CLINICAL USE

Vitamin D analogue:

Promotes intestinal calcium absorption

Suppresses PTH production and release

DOSE IN NORMAL RENAL FUNCTION

Orally: 250 nanograms daily or on alternate days, increased if necessary in steps of 250 nanograms at intervals of 2–4 weeks. Usual dose 0.5–1 micrograms daily

IV: treatment of hyperparathyroidism in haemodialysis patients: initially 500 nanograms (10 nanograms/kg) 3 times a week, increased if necessary in steps of 250–500 nanograms at intervals of 2–4 weeks. Usual dose 0.5–3 micrograms 3 times a week after dialysis

PHARMACOKINETICS

Molecular weight :416.6

%Protein binding :99.9

%Excreted unchanged in urine : 7–10

Volume of distribution (L/kg) :No data

half-life – normal/ESRD (hrs) :9–10/18–20

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function. Titrate to response

10 to 20 : Dose as in normal renal function. Titrate to response

<10 : Dose as in normal renal function. Titrate to response

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unlikely to be dialysed. Dose as in normal renal function

HD :Not dialysed. Dose as in normal renal function

HDF/high flux :Not dialysed. Dose as in normal renal function

CAV/VVHD :Unknown dialysability. Dose as in normal renal function

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

The effects of vitamin D may be reduced in patients taking barbiturates or anticonvulsants

Increased risk of hypercalcaemia if thiazides given with vitamin D

ADMINISTRATION

Reconstition

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Route

Oral, IV

Rate of Administration

Bolus

Comments

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OTHER INFORMATION

Check plasma calcium concentrations at regular intervals (initially weekly)

Dose of phosphate-binding agent may need to be modified as phosphate transport in the gut and bone may be affected

Hypercalcaemia and hypercalciuria are the major side effects, and indicate excessive dosage

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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