One Alpha0.25 mcg

One Alpha is a synthetic vitamin D analog (1α-hydroxycholecalciferol) used in the following clinical settings:

• Established/guideline-supported uses: Management of renal osteodystrophy and secondary hyperparathyroidism associated with chronic kidney disease, including in patients on dialysis.
• Established uses: Hypoparathyroidism and pseudohypoparathyroidism.
• Established uses: Vitamin D-dependent rickets and vitamin D-resistant (hypophosphatemic) rickets/osteomalacia, and nutritional rickets/osteomalacia with malabsorption.
• Adjunct/combination use: Postmenopausal, senile, and glucocorticoid-induced osteoporosis, usually together with adequate calcium intake and as part of a broader osteoporosis management plan.
• Off-label use (reported in literature, not a primary approved indication): Selected cases of osteoporosis-related fracture risk reduction and certain hypocalcemic states, at the discretion of a specialist physician.

The exact indication and dose of One Alpha should always be individualized by a treating physician based on the underlying condition, serum calcium/phosphate, and renal or hepatic function.

Each capsule/soft gelatin capsule of Alfacalcidol contains Alfacalcidol BP/USP as the active ingredient, commonly available in strengths of 0.25 mcg and 0.5 mcg. Oral drop formulations (e.g., 2 mcg/mL) may also be available. Exact excipients and available strengths vary by manufacturer and market.

One Alpha is a synthetic analog of vitamin D, chemically known as 1α-hydroxycholecalciferol (1α-hydroxyvitamin D3). Unlike native vitamin D3, which requires sequential hydroxylation in both the liver (25-hydroxylation) and kidney (1α-hydroxylation) to become fully active, One Alpha only requires a single hepatic 25-hydroxylation step to be converted to the biologically active hormone 1,25-dihydroxyvitamin D3 (calcitriol).

This feature makes One Alpha particularly useful in patients whose renal 1α-hydroxylase activity is impaired, such as those with chronic kidney disease, since it bypasses the need for renal activation.

One Alpha belongs to the therapeutic class of Vitamin D analogs / Antihypocalcemic and bone metabolism regulating agents, used in the treatment and prevention of disorders of calcium and phosphate metabolism.

Mechanism: Alfacalcidol is a prodrug that undergoes rapid 25-hydroxylation in the liver to form 1,25-dihydroxyvitamin D3 (calcitriol), the active hormonal form of vitamin D. Because this activation step occurs in the liver rather than the kidney, Alfacalcidol remains effective even when renal function (and hence renal 1α-hydroxylase activity) is significantly reduced.

The active metabolite binds to the vitamin D receptor (VDR) in target tissues, where it:

• Increases intestinal absorption of calcium and phosphate.
• Promotes renal tubular reabsorption of calcium.
• Regulates osteoblast and osteoclast activity to support normal bone mineralization and remodeling.
• Suppresses excessive parathyroid hormone (PTH) synthesis and secretion, which is useful in secondary hyperparathyroidism of chronic kidney disease.

Pharmacokinetics: Alfacalcidol is well absorbed orally, hydroxylated rapidly in the liver, with onset of biological effect typically within hours and a biological half-life of the active metabolite of roughly 1-2 days; effects on serum calcium may persist for days to weeks after discontinuation because of storage in fat and slow clearance of the active metabolite.

One Alpha is administered orally, usually once daily, with or without food, and can be swallowed with a glass of water at approximately the same time each day for consistency. Oral drop formulations should be measured and administered using the dropper/device provided by the manufacturer. Do not change the dose or frequency without consulting the prescribing physician.

One Alpha has the following clinically significant interactions:

• Other vitamin D analogs, calcitriol, or calcium supplements: Concurrent use increases the risk of additive hypercalcemia; avoid combining unless specifically directed by a physician.
• Thiazide diuretics: May increase the risk of hypercalcemia when combined with One Alpha; calcium levels should be monitored more closely.
• Digoxin and other cardiac glycosides: If hypercalcemia develops during concurrent use with One Alpha, the risk of digoxin toxicity and cardiac arrhythmia is increased; ECG and calcium monitoring is advised.
• Magnesium-containing antacids: Risk of hypermagnesemia, particularly in patients with renal failure on dialysis taking One Alpha.
• Enzyme-inducing drugs (e.g., phenytoin, phenobarbital, rifampicin): May increase hepatic metabolism of One Alpha and reduce its effect.
• Cholestyramine, orlistat, or mineral oil: May reduce gastrointestinal absorption of One Alpha; separate dosing times where possible.
• Ketoconazole and similar agents: May inhibit hepatic hydroxylation, reducing conversion of One Alpha to its active form.

Most adverse effects of One Alpha are related to excessive vitamin D activity leading to hypercalcemia and/or hypercalciuria. These include:

• Common: Nausea, vomiting, constipation, dry mouth, headache, weakness, and anorexia (loss of appetite).
• Related to hypercalcemia (dose-dependent, more likely with prolonged high-dose use): Polyuria, polydipsia, drowsiness, confusion, muscle or bone pain, metallic taste, and pruritus (itching).
• Less common but serious: Soft tissue and vascular calcification, worsening renal function, and cardiac arrhythmia (particularly if hypercalcemia is untreated) — see Contraindications and Precautions for related safety information.
• Rare: Hypersensitivity reactions.

Patients should seek prompt medical advice if symptoms of hypercalcemia occur.

Pregnancy: Data on the use of One Alpha in pregnancy are limited. It should be used during pregnancy only if clearly needed and if the potential benefit justifies the potential risk to the fetus; maternal serum calcium should be monitored closely, since maternal hypercalcemia has been associated with fetal harm. Consult a physician before use in pregnancy.

Lactation: One Alpha and its active metabolites may pass into breast milk and could theoretically contribute to infant hypercalcemia. It should be used during breastfeeding only under medical supervision, weighing the benefit to the mother against potential risk to the infant, with monitoring of the infant if used.

Use One Alpha with caution and under regular medical supervision. Key precautions include:

• Hypercalcemia/hypercalciuria: Regular monitoring of serum calcium, phosphate, and renal function is required, particularly during dose titration; risk increases with concurrent calcium supplementation (see Interactions).
• Concurrent vitamin D sources: Avoid concomitant use of other vitamin D analogs or supplements with One Alpha unless specifically directed by a physician, due to additive hypercalcemia risk.
• Cardiac patients: Extra caution and calcium monitoring are needed in patients on digoxin or other cardiac glycosides because of the arrhythmia risk associated with hypercalcemia.
• Individualized dosing: Dose must be individualized and monitored by a physician experienced in renal bone disease and calcium metabolism management, especially in patients with chronic kidney disease.
• Dietary calcium: Adequate but not excessive dietary calcium intake should be ensured, per specialist guidance, while on One Alpha.
• Hepatic impairment: Use cautiously as hepatic activation of One Alpha may be impaired (see Dosage and Administration).
• Immobilized patients: May be at higher risk of hypercalcemia due to increased bone resorption.

Overdose of One Alpha can cause vitamin D toxicity and hypercalcemia, with symptoms such as nausea, vomiting, anorexia, constipation, drowsiness, confusion, muscle weakness, polyuria, polydipsia, dehydration, and in severe cases cardiac arrhythmia or renal impairment.

If overdose is suspected, discontinue One Alpha immediately and seek immediate medical attention or contact emergency services/poison control. Management is supportive and includes stopping the drug and any calcium/vitamin D supplements, hydration, and monitoring/correction of serum calcium under medical supervision; in severe or refractory hypercalcemia, hospital-based treatment (including dialysis with a low-calcium dialysate in dialysis patients) may be required. Do not attempt to manage a suspected overdose at home without medical guidance.

Store at room temperature (below 30°C), protected from light and moisture. Keep out of reach of children.

Renal impairment: One Alpha is specifically used in patients with renal impairment/chronic kidney disease, including those on dialysis, since it does not require renal activation; dose must still be carefully individualized and monitored (see Dosage and Administration).

Hepatic impairment: Use with caution as hepatic hydroxylation is required to activate One Alpha; monitor response and adjust dose accordingly.

Elderly: May be more susceptible to hypercalcemia; use the lowest effective dose with close monitoring of serum calcium and renal function.

Pediatric patients: Used in certain pediatric conditions (e.g., renal osteodystrophy, vitamin D-dependent rickets) with weight-based, specialist-supervised dosing; safety and efficacy for indications outside established pediatric use have not been established (see Pediatric Uses).

Pregnancy and lactation: See Pregnancy and Lactation section for detailed guidance.

Treatment with One Alpha for chronic conditions such as renal osteodystrophy, hypoparathyroidism, or osteoporosis is generally long-term/ongoing, continued for as long as clinically indicated. The treating physician determines duration based on the underlying condition, response to therapy, and regular monitoring of serum calcium, phosphate, and renal function; therapy should not be stopped or altered without medical advice.

Vitamin D analogs; agents affecting bone and mineral (calcium/phosphate) metabolism.

Alfacalcidol (1α-hydroxycholecalciferol) is a prodrug that undergoes a single hepatic 25-hydroxylation step to form the biologically active hormone 1,25-dihydroxyvitamin D3 (calcitriol), bypassing the renal 1α-hydroxylation step normally required to activate native vitamin D. The active metabolite binds vitamin D receptors to increase intestinal calcium and phosphate absorption, promote renal calcium reabsorption, regulate bone remodeling, and suppress parathyroid hormone secretion, thereby helping normalize calcium and phosphate homeostasis and bone mineralization.

One Alpha is used in pediatric patients for specific, well-defined conditions such as renal osteodystrophy associated with chronic kidney disease and vitamin D-dependent or vitamin D-resistant rickets, typically with weight-based dosing (approximately 0.01-0.05 mcg/kg/day) individualized and closely monitored by a pediatric specialist, including regular assessment of serum calcium, phosphate, and growth parameters.

Safety and efficacy of One Alpha for indications or age groups outside these established pediatric uses have not been established; pediatric use should always be under specialist supervision due to the narrow margin between therapeutic and toxic (hypercalcemic) doses in children.