Calcitriol

Trade Names:
Calcijex
- Injection 1 mcg/mL

Trade Names:
Calcitriol Injection
- Injection 2 mcg/mL

Trade Names:
Rocaltrol
- Capsules 0.25 mcg
- Capsules 0.5 mcg
- Solution, oral 1 mcg/mL

Trade Names:
Vetical
- Ointment 3 mcg/g

Pharmacology

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Supply of vitamin D depends mainly on exposure to UV rays of the sun for conversion of 7-dehydrocholesterol in the skin to vitamin D ₃ (cholecalciferol). Vitamin D ₃ is activated in the liver and kidney before fully active as a regulator of calcium and phosphorus metabolism at target tissues. The mechanism of action in the treatment of psoriasis has not been established.

Pharmacokinetics

Absorption

Rapidly absorbed from the intestine. T _max is 3 to 6 h.

Distribution

Approximately 99.9% protein bound.

Metabolism

The first pathway involves 24-hydroxylase to produce calcitroic acid; the second pathway involves hydroxylation and cyclization.

Elimination

The half-life is about 5 to 8 h. About 27% is excreted in the feces and 7% in the urine within 24 h.

Special Populations

The half-life is increased by at least 2-fold.

Studies have not been conducted.

Studies have not been conducted.

The half-life is prolonged.

Studies have not been conducted.

Indications and Usage

Hypocalcemia and resultant metabolic bone disease in patients on chronic renal dialysis.

Secondary hyperparathyroidism and resultant metabolic bone disease in patients with moderate to severe chronic renal failure (CrCl 15 to 55 mL/min) not yet on dialysis.

Hypocalcemia in patients with postsurgical hypoparathyroidism, idiopathic hypoparathyroidism, and pseudohypoparathyroidism.

Treatment of mild to moderate plaque psoriasis.

Unlabeled Uses

Management of psoriatic lesions.

Contraindications

Hypercalcemia or patients with vitamin D toxicity; hypersensitivity to any component of this product.

Dosage and Administration

PO 0.25 mcg/day. If all unsatisfactory response, increase dose by 0.25 mcg/day at 4- to 8-wk intervals. Obtain serum calcium levels at least twice weekly during this titration. If hypercalcemia occurs, immediately discontinue treatment until normocalemia is obtained. Normal or only slightly reduced calcium levels may respond to dosages of 0.25 mcg every other day.

IV 0.02 mcg/kg (1 to 2 mcg) 3 times/wk, every other day. May increase 0.5 to 1 mcg, every 2 to 4 wk. During this titration, obtain serum calcium levels twice weekly.

PO Initial dosage is 0.25 mcg/day in adults and children older than 3 yr of age. Dosage may be increased up to 0.5 mcg/day.

PO 10 to 15 mg/kg/day.

PO Initial dosage is 0.25 mcg/day in the morning. If unsatisfactory response, increase dose at 2- to 4-wk intervals. During this titration, obtain serum calcium levels 2 times/wk. If hypercalcemia occurs, immediately discontinue treatment until normocalemia is obtained.

PO 0.5 to 2 mcg daily.

PO Usually given 0.25 to 0.75 mcg daily.

Topical Apply to affected areas twice daily, morning and evening (max, 200 g/week).

General Advice

• Oral
• Administer prescribed dose without regard to meals, but administer with food if GI upset occurs.
• Administer dose in the morning to patient with hypoparathyroidism.
• Administer prescribed dose of oral solution using disposable graduated oral dispensers supplied with medication.

• Injection
• For IV bolus injection only. Not for intradermal, subcutaneous, IM, or intra-arterial administration.
• Do not administer if particulate matter, cloudiness, or discoloration noted.
• Discard any unused solution. Do not save for future use.

• Ointment
• The topical ointment should not be applied to the eyes, lips, or face.
• Not for oral, opthalmic, or intravaginal use.

Storage/Stability

Store at 59° to 86°F. Protect from light. Do not freeze or refrigerate ointment.

Drug Interactions

Avoid uncontrolled intake of additional calcium-containing preparations.

May reduce intestinal absorption of fat-soluble vitamins.

Calcium absorption–promoting effects of calcitriol may be antagonized by corticosteroids, which inhibit calcium absorption.

Use with caution; may precipitate cardiac arrhythmias.

May reduce endogenous calcitriol concentrations.

Magnesium-containing products may cause hypermagnesemia and should be avoided during calcitriol administration to patients on chronic renal dialysis.

Inhibits endogenous synthesis of calcitriol; therefore, may require higher doses calcitriol if given simultaneously.

Because phosphate transport in the intestine, kidneys, and bones may be affected, the dosage of phosphate-binding agents must be adjusted based on serum phosphate concentration.

Known to induce hypercalcemia by the reduction of calcium excretion.

Therapeutic effects of verapamil may be reduced.

To avoid possible additive effects and hypercalcemia, withhold pharmacologic doses of vitamin D and its derivatives.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Dermatologic

Psoriasis (4%); pruritus (3%); acute blistering dermatitis, erythema, skin burning sensations, skin discomfort (postmarketing).

Genitourinary

Elevated serum creatinine levels.

Urine abnormality (4%); hypercalciuria (3%).

Hypersensitivity

Anaphylaxis (postmarketing).

Lab Tests

Hypercalcemia (24%); abnormal lab tests (8%).

Local

Skin discomfort (3%).

Miscellaneous

Hypersensitivity (pruritis, rash, severe erythematous skin disorder, urticaria, [rare]), erythema multiforme, allergic reaction (eg, hives, swelling of the lips); soft tissue calcification.

Precautions

Pregnancy

Category C .

Lactation

Excreted.

Children

Safety and efficacy not established in dialysis patients; dosing guidelines for oral calcitriol have not been established in children younger than 1 year of age with hypoparathyroidism or younger than 6 years of age with pseudohypoparathyroidism.

Safety and efficacy not established in children.

Elderly

Dose selection should be cautious, starting at the low end of the dosage range.

Hypersensitivity

May occur.

UV light exposure

With use of the ointment, patients should avoid excessive exposure of treated areas to either natural or artificial sunlight, including sunlamps and tanning booths.

Overdosage

Symptoms

Adverse reactions are associated with excessive intake. The early stage symptoms of toxicity include the following: weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain, metallic taste, anorexia, abdominal pain, stomach ache. The late stage symptoms of toxicity include the following: cardiac arrhythmias, hypertension, pruritus, conjunctivitis (calcific), anorexia, weight loss, pancreatitis, polyuria, polydipsia, nocturia, elevated BUN, nephrocalcinosis, hypercholesterolemia, elevated AST/ALT, albuminia, decreased libido, hyperthermia, photophobia, rhinorrhea, ectopic calcification, overt psychosis, dystrophy, sensory disturbances, dehydration, apathy, arrested growth, UTI, hypercalcemia, hypercalciuria, hyperphosphatemia, overt psychosis (rare).

Patient Information

• Instruct patient to carefully follow the diet and calcium supplementation instructions supplied by health care provider.
• Advise patient to take prescribed dose without regard to meals, but to take with food if GI upset occurs.
• Advise patient or caregiver using oral solution to use disposable graduated oral dispensers supplied with medication.
• Instruct dialysis patient to avoid using any magnesium-containing products (eg, antacids).
• Educate patient regarding signs and symptoms of hypercalcemia. Instruct patient to immediately inform health care provider if they occur.

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