Calcitriol
1,25-dihydroxycholecalciferol
Also known as: Rocaltrol · Calcijex · Active Vitamin D3 · 1,25-dihydroxycholecalciferol · 1-alpha,25 dihydrocholecalciferol · 1,25-DHCC · 1,25-dihidroxyvitamin D3
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| To suppress secondary hyperparathyroidism in CRF | 2.5-3.5 nanograms/kg/day PO (Dogs with refractory hyperparathyroidism may require up to 6 nanograms/kg/day). Alternatively, pulsed-dosing: 20 nanograms/kg twice weekly PO at bedtime on an empty stomach. | PO | q24h or twice weekly | Long-term | 🌎 NA |
| Subacute and chronic maintenance treatment of hypocalcemia | Initially, 20-30 nanograms/kg/day PO divided twice a day for 3-4 days, then 5-15 nanograms/kg/day divided twice a day | PO | q12h | Initial 3-4 days, then maintenance | 🌎 NA |
| Long-term maintenance in animals with hypoparathyroidism | 0.03-0.06 micrograms/kg/day | PO | q24h | Long-term | 🌎 NA |
| Primary idiopathic seborrhea (especially in spaniel breeds) | 10 nanograms/kg PO once daily | PO | q24h | — | 🌎 NA |
- To suppress secondary hyperparathyroidism in CRF: Confirm CRF (creatinine >2 mg/dL) and reduce hyperphosphatemia to <6 mg/dL before starting.
- Long-term maintenance in animals with hypoparathyroidism: Combine with oral calcium to reduce vitamin D dose requirements.
- Primary idiopathic seborrhea (especially in spaniel breeds): Give as far away from the main meal as possible.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| To suppress secondary hyperparathyroidism in CRF | 1.5-3.5 nanograms/kg PO daily given separately from meals (or 2.5-3.5 nanograms/kg PO once daily) | PO | q24h | Long-term | 🌎 NA |
| Long-term maintenance in animals with hypoparathyroidism | 0.03-0.06 micrograms/kg/day | PO | q24h | Long-term | 🌎 NA |
- To suppress secondary hyperparathyroidism in CRF: Remove oil from capsule, dilute in corn oil, then give the appropriate volume.
- Long-term maintenance in animals with hypoparathyroidism: Combine with oral calcium to reduce vitamin D dose requirements.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Calcitriol is the active, hormonal form of vitamin D. In veterinary medicine, it is primarily utilized to manage hypocalcemia (often secondary to hypoparathyroidism) and to suppress secondary hyperparathyroidism in chronic kidney disease (CKD). It may also have benefits in treating primary idiopathic seborrhea in certain dog breeds.
Clinical Pearl: In healthy animals, the kidneys produce the enzyme 1-alpha-hydroxylase, which converts inactive vitamin D into its active form (calcitriol). In chronic renal failure, the loss of functional renal mass leads to a deficiency of this enzyme. Supplementing with calcitriol bypasses this metabolic defect, directly suppressing parathyroid hormone (PTH) synthesis and preventing or treating renal secondary hyperparathyroidism (renal osteodystrophy).
Mechanism of action
Calcitriol binds to the intracellular Vitamin D Receptor (VDR) in target tissues (intestine, bone, kidney, and parathyroid gland) to regulate calcium and phosphorus homeostasis.
- Intestine: Upregulates the synthesis of calcium-binding proteins (e.g., calbindin) → significantly enhances the GI absorption of calcium and phosphorus.
- Kidney: Promotes renal tubular reabsorption of calcium.
- Parathyroid Gland: Directly binds to VDRs on the parathyroid gland → inhibits the transcription of the PTH gene, reducing PTH synthesis and secretion.
- Bone: Works synergistically with PTH to stimulate osteoclast activity, mobilizing calcium and phosphorus into the extracellular fluid.
Unlike other forms of vitamin D (like cholecalciferol or ergocalciferol), calcitriol does not require hepatic or renal activation, resulting in a rapid onset of action (approximately 1 day) and a short half-life.
Safety & warnings
Contraindications
- Hypercalcemia
- Hyperphosphatemia (Calcium x Phosphorus product > 70)
- Vitamin D toxicity
- Malabsorption syndromes
- Abnormal sensitivity to vitamin D effects
Adverse effects
- Hypercalcemia
- Hypercalciuria
- Polydipsia
- Polyuria
- Anorexia
- Tissue mineralization (if given with hyperphosphatemia)
Precautions
Use with extreme caution in patients with hyperphosphatemia; calcium and phosphorus levels should be in the low-normal range before beginning treatment to prevent soft tissue mineralization. Use with caution in animals susceptible to calcium oxalate uroliths due to the risk of hypercalciuria. Calcitriol is teratogenic at high doses (FDA Category C). Serum cholesterol levels may be falsely elevated by vitamin D analogs when using the Zlatkis-Zak reaction.
Drug interactions
Use with calcitriol may induce hypercalcemia.
Can nullify the effects of vitamin D analogs.
Patients are highly sensitive to the arrhythmogenic effects of hypercalcemia; intensified monitoring is required.
Patients are sensitive to the effects of hypercalcemia; intensified monitoring is required.
May induce hepatic enzyme systems and increase the metabolism of Vitamin D analogs, thus decreasing their activity.
May cause hypercalcemia when given in conjunction with Vitamin D analogs.
Monitoring
- Serum calcium (baseline, 1 week, then every 2-4 weeks/6 months depending on protocol)
- Serum phosphorus
- Serum creatinine
- Serum PTH levels (especially in cats or refractory cases)
- Clinical efficacy (improved appetite, activity level, slowed progression of disease)
Pharmacokinetics
Absorption
Readily absorbed from the GI tract (small intestine) if fat absorption is normal. Bile is required for adequate absorption; patients with steatorrhea, liver, or biliary disease will have diminished absorption.
Overdose
Overdosage can cause hypercalcemia, hypercalciuria, and hyperphosphatemia.
- Acute Ingestion: Manage using established protocols for GI decontamination. Orally administered mineral oil may reduce absorption and enhance fecal elimination.
- Chronic Overdosage: Hypercalcemia secondary to chronic dosing should be treated by first temporarily discontinuing (not just dose reduction) calcitriol and exogenous calcium therapy.
- Severe Hypercalcemia: May require treatment with furosemide, calcium-free IV fluids (e.g., normal saline), urine acidification, and corticosteroids.
Available products
Formulations
- Oral capsules
- Oral solution
- Injection
- Topical
Human-labeled
- Calcitriol Oral Capsules: 0.25 micrograms & 0.5 micrograms (Rocaltrol)
- Calcitriol Oral Solution: 1 microgram/mL (Rocaltrol)
- Calcitriol Injection: 1 microgram/mL & 2 micrograms/mL (Calcijex)
- Topical formulations
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Protect from light. Store in tight, light-resistant containers at room temperature. The injection does not contain preservatives and remaining drug should be discarded after opening the ampule.
Client information
Calcitriol is a potent form of vitamin D used to help balance your pet's calcium levels or manage kidney disease complications. Because the doses required for pets are extremely small, the medication often needs to be specially compounded by a pharmacy.
- Administration Timing: If using lower doses (<3.5 nanograms/kg/day), give with the morning meal. If using higher doses (>5 nanograms/kg/day), administer at bedtime on an empty stomach to reduce the chance of calcium spiking.
- Watch for Hypercalcemia (High Calcium): Contact your veterinarian immediately if you notice increased thirst (polydipsia), increased urination (polyuria), or loss of appetite (anorexia).
- Watch for Hypocalcemia (Low Calcium): If treating for low calcium, watch for muscle tremors, facial twitching, stiffness, weakness, uncoordinated walking (ataxia), behavioral changes, or seizures.
- Dietary Supplements: Do not give your pet any over-the-counter calcium or vitamin D supplements without explicit instructions from your veterinarian.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.