ONE ALPHA CAPSULES 0,25 ug

Indications

• Chronic renal failure
• Renal bone disease
• Hypoparathyroidism
• Vitamin D dependent rickets

Dosage

Children: Refer to BNF for Children for specific dosing recommendations.

Adults: Refer to BNF for specific dosing recommendations.

Mechanism of action

In conditions such as chronic renal failure and hypoparathyroidism, the kidneys' ability to hydroxylate vitamin D is diminished, resulting in insufficient production of 1,25-dihydroxyvitamin D. Alfacalcidol serves as an active and potent analog that compensates for this deficiency, promoting the activities associated with endogenous 1,25-dihydroxyvitamin D.

Pharmacodynamics

Alfacalcidol increases serum calcium levels by enhancing intestinal absorption of calcium, promoting calcium reabsorption from bones, and possibly facilitating renal reabsorption of calcium. It also has a modest effect on intestinal phosphorus absorption. The drug's effects on calcium and phosphorus levels are dose-related and can be observed within three days of administration. Notably, serum calcium levels rise while parathyroid hormone and alkaline phosphatase levels typically normalize within five days of starting treatment. In contrast, discontinuation of alfacalcidol can reverse these effects within three days.

Pharmacokinetics

Alfacalcidol is absorbed efficiently from the gastrointestinal tract, with peak plasma concentrations occurring within a few hours of administration. It undergoes hepatic metabolism before exerting its effects. The pharmacokinetics may vary depending on the patient's renal function, especially in those with chronic renal failure, where metabolism and clearance may be altered. The time required to achieve normal calcium levels can extend to several months with daily oral therapy.

Adverse effects

• Hypercalcemia
• Nausea
• Vomiting
• Constipation
• Abdominal pain
• Weakness
• Headache
• Fatigue
• Dry mouth
• Metallic taste

Interactions

• Thiazide diuretics may enhance the risk of hypercalcemia.
• Calcium supplements may increase the risk of hypercalcemia when used concurrently.
• Certain anticonvulsants (e.g., phenytoin, phenobarbital) may reduce the effectiveness of alfacalcidol.

Precautions

• Monitor serum calcium and phosphate levels regularly during treatment.
• Use with caution in patients with a history of kidney stones.
• Patients with hypercalcemia or vitamin D toxicity should not use alfacalcidol.
• Evaluate renal function before starting therapy.

Pregnancy

Alfacalcidol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Consultation with a healthcare provider is essential.

Breast-feeding

Alfacalcidol is excreted in breast milk, and caution should be exercised when administering to nursing mothers.

Storage

Store in a cool, dry place, away from light. Do not refrigerate.

Formulations

• Capsules
• Oral solution

Mechanism of action

In conditions like chronic renal failure, renal bone disease, hypoparathyroidism, and vitamin D dependent rickets, the kidneys' capacity for 1α-hydroxylation is impaired, leading to reduced production of endogenous 1,25-dihydroxyvitamin D and aberrated mineral metabolism. As an active and potent analog of vitamin D, alfacalcidol works to restore the functions and activities of endogenous 1,25-dihydroxyvitamin D.

Pharmacodynamics

Alfacalcidol works to increase serum levels of calcium by stimulating intestinal calcium absorption, reabsorption of calcium from bone, and possibly the renal reabsorption of calcium. It also modestly promotes intestinal phosphorus absorption. In patients with renal failure, alfacalcidol increased intestinal calcium and phosphorus absorption in a dose-related manner. This increase in calcium and phosphorus levels occurs within three days following drug administration: this effect was reversed within three days of drug discontinuation. In patients with chronic renal failure, serum calcium levels were elevated while parathyroid hormone and alkaline phosphatase levels returned to normal levels within five days following alfacalcidol administration. Since alfacalcidol suppresses parathyroid hormone, a reduction in parathyroid hormone levels is achieved more rapidly in patients on intermittent intravenous therapy, with significant reductions occurring within three months of therapy. In patients receiving daily oral therapy of alfacalcidol, the time it takes alfacalcidol to normalize plasma calcium levels may be up to several months, possibly reflecting calcium being utilized for bone mineralization. In patients with nutritional osteomalacia, alfacalcidol increased calcium absorption with six hours of oral administration and the effects peaked at 24 hours.