Calcitriol

Calcitriol is the active form of vitamin D used across several products and routes for a range of conditions involving calcium, bone, and skin.

• Dialysis patients (oral and IV): Calcitriol capsules, Rocaltrol capsules, Calcitriol Oral Solution, Rocaltrol oral solution, and Calcitriol injection all treat low blood calcium (hypocalcemia) and the bone disease that comes with it in people on chronic kidney dialysis. They can also reduce elevated parathyroid hormone levels.
• Pre-dialysis patients (oral): Calcitriol capsules, Rocaltrol capsules, Calcitriol Oral Solution, and Rocaltrol oral solution treat secondary hyperparathyroidism (overactive parathyroid glands driven by kidney disease) and its resulting bone disease in people with moderate to severe chronic kidney failure who are not yet on dialysis.
• Hypoparathyroidism (oral): Calcitriol capsules, Rocaltrol capsules, Calcitriol Oral Solution, and Rocaltrol oral solution treat low calcium and its complications in people with postsurgical hypoparathyroidism, idiopathic hypoparathyroidism, and pseudohypoparathyroidism.
• Plaque psoriasis (topical): Vectical Ointment and Calcitriol Ointment are applied to the skin to treat mild to moderate plaque psoriasis in adults and children 2 years and older. These topical products have not been evaluated in people with disorders of calcium metabolism.

Normally, your skin makes vitamin D from sunlight, and your liver and kidneys convert it step by step into calcitriol — the most potent active form. When kidneys are failing, they can't make enough calcitriol, so calcium levels drop and the parathyroid glands overreact. Calcitriol acts primarily at the intestine and bones: it ramps up calcium absorption from food and helps regulate phosphorus, correcting the imbalance that drives bone disease and excess parathyroid hormone. When applied to the skin, calcitriol works as a vitamin D analog to help normalize skin cell growth in plaque psoriasis, though the skin mechanism is separate from its calcium-regulating effects.

How calcitriol is taken depends on the product and condition being treated — follow your prescriber's exact instructions.

• Oral capsules and oral solution (Calcitriol and Rocaltrol): taken by mouth, usually once daily; always started at the lowest effective dose and adjusted based on blood calcium levels.
• Intravenous injection (Calcitriol injection): given by a healthcare provider into a vein, typically three times a week, roughly every other day.
• Topical ointment (Vectical Ointment, Calcitriol Ointment): applied to affected skin twice daily, morning and evening; not for use on eyes, lips, or face.

For oral forms, maintaining adequate calcium intake through food or supplements is part of the treatment plan — your doctor will guide you on this. Never change your dose on your own.

Most side effects of oral or intravenous calcitriol are related to getting too much calcium — watch for early warning signs and report them promptly.

• Weakness, headache, or drowsiness
• Nausea, vomiting, dry mouth, or metallic taste
• Constipation, stomach pain, or loss of appetite
• Muscle or bone pain
• Excessive thirst and urination (signs of high calcium)
• Skin rash, itching, or hives (allergic reaction)

More serious reactions — including irregular heartbeat, calcium deposits in tissues, kidney problems, high blood pressure, or a rare severe skin reaction — require immediate medical attention. If you notice swelling of the lips or a widespread rash, seek care right away.

The most critical risk with calcitriol is hypercalcemia (too much calcium in the blood). Because calcitriol is the most potent active vitamin D metabolite, even small excesses can push calcium to dangerous levels. High calcium can cause calcium to deposit in blood vessels, kidneys, and other soft tissues — potentially permanently. Regular blood tests are essential, and all other vitamin D products must be stopped during calcitriol therapy to avoid additive effects.

In kidney failure, calcitriol also raises phosphorus levels. A high calcium-times-phosphorus product in the blood increases the risk of soft-tissue calcification. Dialysis patients need a phosphate-binding agent and a low-phosphate diet. Magnesium-containing antacids must be avoided in dialysis patients to prevent dangerously high magnesium levels. Patients on digitalis (digoxin) require especially careful monitoring because high calcium can cause life-threatening heart arrhythmias.

Calcitriol interacts with several common medications and supplements — always give your prescriber and pharmacist a full list of everything you take.

• Vitamin D products and calcium supplements: Additive effects can cause dangerous hypercalcemia — avoid unless specifically directed.
• Thiazide diuretics: These water pills reduce calcium loss in urine and can push calcium levels too high when combined with calcitriol.
• Digoxin (heart medication): High calcium caused by calcitriol can trigger serious heart rhythm problems in people taking digoxin.
• Cholestyramine: This cholesterol medication can reduce how well calcitriol is absorbed from the gut.
• Phenytoin or phenobarbital (seizure medications): These speed up vitamin D breakdown, which may reduce calcitriol's effectiveness.
• Ketoconazole (antifungal): May interfere with the enzymes that make and break down calcitriol.
• Corticosteroids: Work against calcitriol by blocking calcium absorption.
• Magnesium-containing antacids: Can cause hypermagnesemia (dangerously high magnesium) in dialysis patients — avoid during calcitriol therapy.

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not use calcitriol if you have high blood calcium (hypercalcemia) or signs of vitamin D toxicity.
• Tell your doctor about any known allergy or sensitivity to calcitriol or related vitamin D drugs.
• The topical ointments (Vectical, Calcitriol Ointment) have not been studied in people with known or suspected calcium metabolism disorders — discuss with your doctor first.
• Tell your doctor if you are pregnant or planning to become pregnant; calcitriol can enter fetal circulation.
• Calcitriol passes into breast milk at low levels — discuss the risks and benefits with your doctor if you are breastfeeding.
• Kidney disease affects how calcitriol behaves in the body — the drug stays active longer in people with chronic kidney failure or on hemodialysis, making monitoring especially important.
• If you take digoxin, thiazide diuretics, seizure medications, or corticosteroids, your doctor will need to monitor you more closely.
• Dialysis patients must avoid magnesium-containing antacids during therapy.

Too much calcitriol causes high calcium (hypercalcemia), high phosphorus, and high urine calcium. Symptoms range from weakness, nausea, and dry mouth to confusion, irregular heartbeat, and calcium deposits in organs. If an overdose is suspected, calcitriol should be stopped immediately, calcium supplements should be withdrawn, and a low-calcium diet started — calcium usually returns to normal within 2 to 7 days. In severe cases, especially in dialysis patients, dialysis against a calcium-free solution may be needed.

Calcitriol's main effects happen at the intestine and bones: it actively increases calcium absorption from food eaten, helps regulate phosphorus transport, and can lower elevated parathyroid hormone levels. In people with kidney failure, these actions help correct the low calcium and excess parathyroid hormone that drive bone disease (renal osteodystrophy). A single dose remains pharmacologically active for about 3 to 5 days. Notably, calcitriol treatment has not been shown to speed up the loss of remaining kidney function in predialysis patients.

After an oral dose, calcitriol is absorbed quickly from the intestine, with blood levels peaking within 3 to 6 hours. It is very tightly bound to proteins in the blood and is broken down in the kidney and other tissues before being eliminated mainly through the feces. In people with normal kidney function, the half-life (the time for half the drug to leave the body) is about 5 to 8 hours, but this can more than double in people with chronic kidney failure or on hemodialysis — meaning the drug stays active longer in those patients and needs more careful monitoring. Calcitriol can also pass into breast milk and fetal circulation at low levels.

Store at 20° to 25°C (68°-77°F) .