Dihydrotachysterol (Vitamin D)
Dihydrotachysterol (Vitamin D) is used in veterinary medicine for hypocalcemia associated with hypoparathyroidism.
Group
Vitamin D analogue
Mechanism of Action
Increases intestinal calcium absorption and calcium availability.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hypocalcemia | 0.01 mg/kg | PO | Every 24 h | |
| Acute hypocalcemia — Initial | 0.02 mg/kg | PO | ||
| Acute hypocalcemia — Maintenance | 0.01–0.02 mg/kg | PO | Every 24–48 h | Adjust to serum calcium. Higher 0.1–0.3 mg/kg doses are mentioned without a defined schedule and are not default escalation doses. |
| Hypoparathyroidism induction taper | Reference only | PO | Start 0.03 mg/kg daily until a response, then 0.02 mg/kg daily for 2 days, followed by 0.01 mg/kg daily. Maintain inpatient monitoring until calcium is stable at 8–9.5 mg/dL; check weekly initially and every 2–3 months during stable long-term treatment. |
Cat
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Hypocalcemia | 0.01 mg/kg | PO | Every 24 h | |
| Acute hypocalcemia — Initial | 0.02 mg/kg | PO | ||
| Acute hypocalcemia — Maintenance | 0.01–0.02 mg/kg | PO | Every 24–48 h | Adjust to serum calcium. Higher 0.1–0.3 mg/kg doses are mentioned without a defined schedule and are not default escalation doses. |
| Hypoparathyroidism induction taper | Reference only | PO | Start 0.03 mg/kg daily until a response, then 0.02 mg/kg daily for 2 days, followed by 0.01 mg/kg daily. Maintain inpatient monitoring until calcium is stable at 8–9.5 mg/dL; check weekly initially and every 2–3 months during stable long-term treatment. | |
| Chronic hypocalcemia — Initial | 0.02–0.03 mg/kg | PO | Every 24 h | With oral calcium supplementation. |
| Chronic hypocalcemia — Maintenance | 0.01–0.02 mg/kg | PO | Every 24–48 h |
Indications
- Hypocalcemia associated with hypoparathyroidism
Contraindications
- Pregnancy
- Hypercalcemia
Interactions
- Calcium supplements and thiazides increase hypercalcemia risk.
Adverse effects
- Hypercalcemia from excess dosing
Toxicity
Overdose causes hypercalcemia and tissue mineralization.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Dihydrotachysterol capsule 0.125 mg | Capsule | 0.125 mg / capsule | PO |
| Dihydrotachysterol oral liquid 0.5 mg/mL Historical presentation contains 20% alcohol. | Oral Liquid | 0.5 mg / mL | PO |
Monitoring and Administration
Titrate to measured serum calcium; monitor renal function and distinguish total from ionized calcium.