Doxercalciferol

Doxercalciferol is a synthetic vitamin D analog approved for the treatment of secondary hyperparathyroidism in adults with chronic kidney disease (CKD). The specific approved uses depend on the form:

• Doxercalciferol capsules are approved for adults with Stage 3 or Stage 4 CKD who are not yet on dialysis
• Doxercalciferol capsules are also approved for adults with CKD who are on dialysis
• Doxercalciferol injection is approved for adults with CKD who are on dialysis only

Doxercalciferol is not active on its own — the liver converts it into its working form using an enzyme called CYP27. That active form then binds to vitamin D receptors throughout the body, triggering signals that tell the parathyroid glands to make less PTH (parathyroid hormone). This helps bring overactive PTH levels back into a safe range. Importantly, the kidneys are not needed for this activation step, which makes doxercalciferol suitable for people with significant kidney disease.

How doxercalciferol is taken depends on both the form and your stage of kidney disease. Your prescriber will set and adjust your dose based on regular blood tests — there is no single fixed dose for everyone.

• Capsules for Stage 3 or 4 CKD: taken by mouth once daily
• Capsules for CKD on dialysis: taken by mouth three times weekly at dialysis sessions (no more often than every other day)
• Injection for CKD on dialysis: given into a vein by a healthcare professional at the end of each dialysis session, three times weekly (no more often than every other day)

If you take the capsule form, be sure to separate it from cholestyramine or mineral oil by at least one hour before or four to six hours after, to make sure the medication is absorbed properly. Always follow your prescriber's specific instructions and never adjust your dose on your own.

The most commonly reported side effects differ slightly depending on whether you have CKD on dialysis or pre-dialysis CKD:

• Headache
• Nausea or vomiting
• Swelling (edema)
• Fatigue or general discomfort (malaise)
• Dizziness
• Shortness of breath (dyspnea)
• Itching (pruritus)
• Slow heart rate (bradycardia)
• Constipation, low appetite, or stomach upset
• Anemia or low white blood cell count

Seek medical attention right away if you develop signs of high calcium — such as feeling very tired, confused, unusually thirsty, or having nausea, vomiting, or constipation — or if you experience any signs of a severe allergic reaction, including swelling of the face or throat, difficulty breathing, or loss of consciousness.

• High calcium (hypercalcemia): The most important risk. Too much calcium can cause heart rhythm problems, seizures, and — over time — calcium deposits in blood vessels and other tissues. Risk increases if you also use high-dose calcium supplements, thiazide diuretics, or other vitamin D products. Calcium levels are monitored regularly and your dose will be adjusted if levels rise too high.
• Serious allergic reactions: Rare but life-threatening reactions, including anaphylaxis, have been reported with the injectable form in hemodialysis patients. Symptoms include swelling of the face, lips, tongue or airway, very low blood pressure, chest discomfort, and cardiopulmonary arrest. Some cases have been fatal. Report any unusual reaction immediately.
• Digitalis toxicity: If you take a digitalis heart medication (like digoxin), high calcium caused by doxercalciferol can make that drug more toxic. Your doctor will monitor you more closely.
• Adynamic bone disease: If PTH is suppressed too far below normal, bones can stop remodeling properly, raising fracture risk. Regular PTH monitoring helps prevent this.

Doxercalciferol can interact with several medications and supplements — always tell your care team everything you take:

• High-dose calcium supplements or other vitamin D products — can push blood calcium too high
• Thiazide diuretics (certain water pills) — reduce kidney excretion of calcium, raising hypercalcemia risk further
• Digitalis medications (e.g., digoxin) — elevated calcium from doxercalciferol can increase the toxicity of these heart drugs
• CYP450 inhibitors (e.g., ketoconazole, erythromycin) — can block the liver from converting doxercalciferol into its active form, reducing effectiveness
• Enzyme inducers (e.g., phenobarbital, glutethimide) — can alter how the liver activates doxercalciferol, possibly requiring a dose adjustment
• Magnesium-containing products (e.g., magnesium antacids) — avoid using together in dialysis patients, as magnesium levels can rise to dangerous levels
• Cholestyramine (capsule form only) — can block absorption of doxercalciferol; separate doses by at least 1 hour before or 4–6 hours after
• Mineral oil or fat-altering substances (capsule form only) — can reduce absorption; separate doses similarly

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 if you currently have high blood calcium (hypercalcemia) or signs of vitamin D toxicity
• Do not use if you have a known allergy to doxercalciferol or any ingredient in the product — serious allergic reactions including anaphylaxis have been reported
• Tell your doctor if you take digitalis heart medications — increased monitoring is needed
• Tell your doctor if you have liver disease or impairment — the drug may not be properly activated, and closer monitoring of PTH, calcium, and phosphorus is required
• Pregnancy: Limited safety data are available. CKD itself carries risks during pregnancy including high blood pressure, preeclampsia, and preterm delivery. Discuss the risks and benefits with your doctor.
• Breastfeeding: It is not known whether doxercalciferol passes into breast milk. Breastfed infants should be watched for signs of high calcium (e.g., seizures, vomiting, constipation, weight loss).
• Children: Safety and effectiveness in pediatric patients have not been established.
• Older adults: Use cautiously, typically starting at lower doses, because older patients are more likely to have liver or heart issues and may take multiple other medications.

Taking too much doxercalciferol can lead to dangerously high levels of calcium, calcium in the urine, and elevated phosphorus in the blood. If an overdose is suspected, the medication should be stopped and supportive medical care started right away, with calcium levels checked until they return to normal. Based on how this drug behaves, dialysis is not expected to remove it from the blood.

Doxercalciferol works by reducing PTH (parathyroid hormone) levels through its active form binding to vitamin D receptors. By activating these receptors, it signals the parathyroid glands to produce less PTH, helping to bring elevated levels back into a safe range. The goal of treatment is to maintain PTH within a target therapeutic range while keeping calcium and phosphorus levels normal — this balance is monitored closely throughout therapy.

After the injection form is given, the active metabolite reaches peak blood levels at around 8 hours. With the oral capsule, peak levels are reached at about 11 to 12 hours. The liver activates doxercalciferol using an enzyme called CYP27 — the kidneys are not required for this step. The active form stays in the body for a while: its half-life (the time it takes for half the drug to leave the body) is roughly 32 to 37 hours after an oral dose, and can extend up to 96 hours in some people. Hemodialysis causes a temporary rise in drug levels in the blood but does not actually remove the active form from circulation.

Store at 20° to 25°C (68° to 77°F); excursions permitted between 15° and 30°C (59° and 86°F). Store unopened vial in original carton. Store for up to 3 days at 2° to 8°C (36° to 46°F).