Drug Guide
Calcitriol
Classification
Therapeutic: Mineral and Bone Disorder Agent
Pharmacological: Vitamin D Analog
FDA Approved Indications
- Hypocalcemia associated with chronic kidney disease (CKD)
- Secondary hyperparathyroidism in CKD
- Osteomalacia
Mechanism of Action
Calcitriol, the active form of vitamin D, enhances intestinal absorption of calcium and phosphorus. It also regulates calcium and phosphate homeostasis, suppresses parathyroid hormone synthesis, and promotes bone mineralization.
Dosage and Administration
Adult: Dosing varies based on indication and patient response. Typically, 0.25 mcg once daily, adjusted as needed.
Pediatric: Dosing is individualized based on age, weight, and clinical response.
Geriatric: Start at the lower end of dosing range due to increased sensitivity and risk factors.
Renal Impairment: Use with caution and monitor calcium levels regularly; doses may need adjustment.
Hepatic Impairment: Data limited; use with caution, monitor calcium levels.
Pharmacokinetics
Absorption: Well-absorbed orally with high bioavailability.
Distribution: Wide distribution, binds heavily to vitamin D-binding protein.
Metabolism: Metabolized in the liver to inactive forms.
Excretion: Excreted primarily via the feces and urine.
Half Life: Approx. 10 hours for calcitriol.
Contraindications
- Hypercalcemia
- Vitamin D toxicity
Precautions
- Monitor calcium, phosphorus, and renal function closely during therapy. Use caution in hyperparathyroidism, granulomatous disorders (e.g., sarcoidosis), and renal failure.
Adverse Reactions - Common
- Hypercalcemia (Less common but significant)
- Nausea, vomiting, constipation (Common)
Adverse Reactions - Serious
- Hypercalcemic crisis (Rare)
- Renal failure (Rare)
Drug-Drug Interactions
- Thiazide diuretics (increases risk of hypercalcemia)
- Digoxin (risk of toxicity with hypercalcemia)
Drug-Food Interactions
- Excessive calcium or vitamin D intake (risk of hypercalcemia)
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor serum calcium, phosphorus, and PTH levels regularly. Watch for signs of hypercalcemia.
Diagnoses:
- Risk for imbalanced calcium concentration
Implementation: Administer with food if instructed, monitor labs regularly, educate patient about signs of toxicity.
Evaluation: Effective management evidenced by normal calcium levels and absence of hypercalcemia symptoms.
Patient/Family Teaching
- Report symptoms of hypercalcemia (nausea, vomiting, constipation, weakness).
- Adhere to prescribed dosing schedule.
- Avoid excess vitamin D and calcium supplementation.
Special Considerations
Black Box Warnings:
- Risk of hypercalcemia leading to vascular and tissue calcification
Genetic Factors: Some genetic conditions affecting vitamin D metabolism may alter response.
Lab Test Interference: May increase serum calcium, phosphorus, and PTH levels.
Overdose Management
Signs/Symptoms: Severe hypercalcemia: nausea, vomiting, weakness, confusion, kidney stones.
Treatment: Discontinue drug, treat hypercalcemia with IV hydration, diuretics, corticosteroids, and bisphosphonates if necessary.
Storage and Handling
Storage: Store at room temperature away from direct light and moisture.
Stability: Stable under recommended storage conditions for the duration of expiration.