디히드로타키스테롤

비타민 D 유사체

**디히드로타키스테롤(DHT)**은 합성 지용성 **비타민 D 유사체**로, 수의학에서는 주로 부갑상선 기능 저하증이나 중증 신장 질환에 속발하는 고칼슘혈증을 관리하는 데 사용됩니다. 역사적으로 중요한 약물이지만, 상업적 공급 문제와 칼시트리올의 더 유리한 약동학적 특성(작용 시작이 빠르고 작용 시간이 짧아 우발적인 고칼슘혈증 관리가 더 용이함)으로 인해 임상적 사용은 대부분 **칼시트리올**로 대체되었습니다. 주요 임상 포인트: * **작용 시작**: 에르고칼시페롤(비타민 D2)보다 빠르지만 칼시트리올보다는 느립니다. * **신장 활성화 우회**: 콜레칼시페롤과 달리 DHT는 활성화되기 위해 신장의 1-알파-수산화효소를 필요로 하지 않으므로 중증 신부전 환자에게 효과적입니다. * **독성 위험**: 약효가 사라지는 데 1~3주가 걸릴 수 있으므로 의인성 고칼슘혈증의 위험이 크며 철저한 모니터링이 필요합니다.

작용 기전: **Dihydrotachysterol** acts as a synthetic analog of 1,25-dihydroxyvitamin D. Its mechanism of action involves several key steps: * **Hepatic Activation**: DHT is absorbed from the GI tract and transported to the liver, where it undergoes hydroxylation by **hepatic 25-hydroxylase** → **25-hydroxydihydrotachysterol** (the active metabolite). * **Receptor Binding**: The active metabolite binds to **Vitamin D Receptors (VDR)** in target tissues (primarily intestine, bone, and kidneys). * **Calcium Homeostasis**: * **Intestine**: Stimulates the synthesis of calcium-binding proteins (e.g., calbindin) → significantly enhances dietary calcium and phosphorus absorption. * **Bone**: Works synergistically with parathyroid hormone (PTH) to promote the accretion and resorption of minerals, mobilizing calcium into the extracellular fluid. * **Kidneys**: Promotes the reabsorption of calcium by the renal tubules. > **Clinical Pearl**: Because the active form of DHT is structurally similar to 1,25-dihydroxyvitamin D, it effectively bypasses the need for **renal 1-alpha-hydroxylase**, an enzyme often deficient in chronic kidney disease.

동물 종별 용량

Cats

Hypocalcemia secondary to hypoparathyroidism · Initially give 0.03 mg/kg PO for several days or until effect is demonstrated, then give 0.02 mg/kg for 2 days, then 0.01 mg/kg per day. · PO · q24h · Pet should remain hospitalized until serum calcium concentration remains stable between 8-9.5 mg/dL. Recheck serum calcium on a weekly basis during early stages of treatment; recheck every 2-3 months long-term. Some dogs and cats that appear to be resistant to treatment on tablets or capsules may respond to the liquid form.
Chronic hypocalcemia with oral calcium tx · Initially: 0.02-0.03 mg/kg/day PO. Maintenance: 0.01-0.02 mg/kg PO q24-48h. · PO · q24-48h

Dogs

Hypocalcemia secondary to hypoparathyroidism · Initially give 0.03 mg/kg PO for several days or until effect is demonstrated, then give 0.02 mg/kg for 2 days, then 0.01 mg/kg per day. · PO · q24h · Pet should remain hospitalized until serum calcium concentration remains stable between 8-9.5 mg/dL. Recheck serum calcium on a weekly basis during early stages of treatment; recheck every 2-3 months long-term. Some dogs and cats that appear to be resistant to treatment on tablets or capsules may respond to the liquid form.

용량은 면허 수의 전문가를 위한 임상 참고 자료입니다. 항상 최신 라벨과 개별 환자에 대해 확인하십시오.

투여 경로

금기

Pre-existing hypercalcemia
Vitamin D toxicity
Malabsorption syndromes
Abnormal sensitivity to the effects of vitamin D

이상반응

Hypercalcemia (manifesting as polydipsia, polyuria, anorexia, vomiting, lethargy)
Nephrocalcinosis (soft tissue mineralization)
Hyperphosphatemia

약물 상호작용

Calcium-containing phosphorus binding agents (e.g., calcium carbonate) · Use with vitamin D analogs may induce severe hypercalcemia.
Corticosteroids · Can nullify the calcium-elevating effects of vitamin D analogs.
Digoxin · Patients are highly sensitive to the arrhythmogenic effects of hypercalcemia; intensified monitoring is required.
Verapamil · Patients are sensitive to the effects of hypercalcemia; intensified monitoring is required.
Mineral oil · May reduce the amount of DHT absorbed from the GI tract.
Sucralfate · May reduce the amount of DHT absorbed from the GI tract.
Cholestyramine · May reduce the amount of DHT absorbed from the GI tract.
Phenytoin · May induce hepatic enzyme systems and increase the metabolism of Vitamin D analogs, thus decreasing their activity.
Barbiturates · May induce hepatic enzyme systems and increase the metabolism of Vitamin D analogs, thus decreasing their activity.
Primidone · May induce hepatic enzyme systems and increase the metabolism of Vitamin D analogs, thus decreasing their activity.
Thiazide diuretics · May cause hypercalcemia when given in conjunction with Vitamin D analogs.

모니터링

Serum calcium levels (closely/twice daily during initial treatment; at least 2-4 times yearly during maintenance)
Serum phosphorus levels (particularly in renal failure patients)
Calcium-phosphorus product (Ca x P)

과용량

### Acute Toxicity Acute ingestions should be managed using established protocols for GI decontamination. **Orally administered mineral oil** may reduce absorption and enhance fecal elimination. ### Chronic Toxicity (Hypercalcemia) Hypercalcemia secondary to chronic dosing is a serious complication. 1. **Discontinue Therapy**: Immediately stop DHT and any exogenous calcium supplementation. 2. **Severe Hypercalcemia Management**: Administer **furosemide**, **calcium-free IV fluids** (e.g., 0.9% normal saline) to promote diuresis, urine acidification, and **corticosteroids** (which decrease intestinal calcium absorption and increase renal excretion). 3. **Monitoring**: Because of the long duration of action of DHT (usually one week and potentially up to 3 weeks), hypercalcemia may persist for an extended period. 4. **Re-initiation**: Restart DHT/calcium therapy at a reduced dosage with diligent monitoring only when serum calcium levels return to the normal range.

VetSheet 약물 레퍼런스는 면허 수의 전문가를 위한 임상 의사결정 보조 도구이며, 전문적 판단이나 제조사의 최신 라벨을 대신하지 않습니다.