カルシウム塩（グルコン酸カルシウム、塩化カルシウム、乳酸カルシウム、グルセプチン酸カルシウム）
カルシウム塩は必須ミネラルサプリメントであり、主に**低カルシウム血症**の治療や予防、および腎不全患者における経口リン吸着剤として使用されます。 注射用カルシウムは、以下の治療に用いられる重要な救急薬です： * **確認されたイオン化低カルシウム血症**（例：子癇/産褥テタニー、原発性副甲状腺機能低下症）。 * **高カリウム血症による心毒性**（例：尿道閉塞の猫、アジソン病クリーゼ）。*臨床のポイント：カルシウムは血清カリウム値を低下させるわけではありません。心筋の閾電位を上昇させ、正常な静止膜電位と閾値の差を回復させることで、致命的な不整脈から心臓を保護します。* * **カルシウム拮抗薬中毒**。 **臨床のポイント：** カルシウム塩の違いを区別することが極めて重要です。**10%塩化カルシウム**は、**10%グルコン酸カルシウム**（9.3 mg/mL）の約3倍の元素カルシウム（27.2 mg/mL）を含んでいます。塩化カルシウムは刺激性が強く、酸性化作用があり、血管外に漏出すると重度の組織壊死を引き起こす危険性があるため、理想的には中心静脈ラインから投与すべきです。末梢静脈からの投与にはグルコン酸カルシウムが推奨されます。
作用機序: Calcium is an essential intracellular and extracellular cation vital for numerous physiological processes: * **Nervous and Musculoskeletal Function:** Facilitates excitation-contraction coupling in cardiac and smooth muscle, and is required for neurotransmitter release at synaptic clefts. * **Cell Membrane Permeability:** Maintains cell membrane integrity and capillary permeability. * **Enzymatic Reactions:** Acts as a crucial cofactor for various enzymatic reactions and the coagulation cascade. * **Hyperkalemia Antagonism:** In hyperkalemia, elevated resting membrane potentials lead to cardiac conduction blocks. Calcium administration **→** raises the threshold potential **→** restores the normal electrical gradient **→** stabilizes the myocardium.
動物種別の用量
- Hypocalcemia · 150-250 mg/kg IV slowly to effect · IV · PRN · Intraperitoneal route may also be used. Monitor respirations and cardiac rate and rhythm.
- Hypocalcemia · Calcium gluconate 23% injection: 25-50 mL IV slowly, or IM or SC (divided and given in several locations, with massage at sites of injection) · IV/IM/SC · PRN
- Hypocalcemia · 150-250 mg/kg IV slowly to effect · IV · PRN · Dosing extrapolated from sheep guidelines. Intraperitoneal route may also be used.
- Hypocalcemia · Calcium gluconate 23% injection: 25-50 mL IV slowly, or IM or SC (divided and given in several locations, with massage at sites of injection) · IV/IM/SC · PRN · Dosing extrapolated from sheep guidelines.
- Hypocalcemia · 94-140 mg/kg IV slowly to effect · IV · PRN · Intraperitoneal route may also be used. Monitor respirations and cardiac rate and rhythm.
- Acute hypocalcemia secondary to hypoparathyroidism · 10% calcium gluconate injection, give 1-1.5 mL/kg IV slowly over 10-20 minutes. Once controlled, add to IV fluids as slow infusion at 60-90 mg/kg/day (of elemental calcium) [converts to 2.5 mL/kg every 6-8 hours of 10% calcium gluconate]. Oral: initially 50-100 mg/kg/day divided 3-4 times daily of elemental calcium. · IV/PO · PRN/CRI/Divided · Monitor ECG. If bradycardia or Q-T interval shortening occurs, slow rate or temporarily discontinue.
- Hypocalcemia secondary to phosphate enema toxicity or puerperal tetany · 10% calcium gluconate injection, give 1-1.5 mL/kg IV slowly over 10-20 minutes. · IV · PRN · Follow guidelines for use of intravenous calcium.
投与経路
禁忌
- Ventricular fibrillation
- Hypercalcemia
有害事象
- Hypercalcemia
- GI irritation and/or constipation (oral administration)
- Mild to severe tissue reactions, pyogranulomatous panniculitis, adipocyte mineralization (IM or SC administration)
- Venous irritation (IV administration)
- Hypotension (if given IV too rapidly)
- Cardiac arrhythmias and cardiac arrest (if given IV too rapidly)
薬物相互作用
- Calcium Channel Blockers (e.g., diltiazem, verapamil) · Intravenous calcium may antagonize the effects of calcium-channel blocking agents.
- Digoxin · Patients on digitalis therapy are more apt to develop arrhythmias if receiving IV calcium; use with extreme caution.
- Magnesium (oral) · May lead to increased serum magnesium and/or calcium, particularly in patients with renal failure.
- Magnesium Sulfate (parenteral) · Parenteral calcium can neutralize the effects of hypermagnesemia or magnesium toxicity secondary to parenteral magnesium sulfate.
- Neuromuscular Blockers (e.g., atracurium, vecuronium, tubocurarine) · Parenteral calcium may reverse the effects of nondepolarizing neuromuscular blocking agents; has been reported to prolong or enhance the effects of tubocurarine.
- Tetracyclines, Fluoroquinolones (oral) · Oral calcium can reduce the amount of these antibiotics absorbed from the GI tract via chelation; separate dosages by at least two hours.
- Potassium Supplements · Patients receiving both parenteral calcium and potassium supplementation may have an increased chance of developing cardiac arrhythmias.
- Thiazide Diuretics · Used in conjunction with large doses of calcium may cause hypercalcemia.
- Vitamin A · Excessive intake may stimulate calcium loss from bone and cause hypercalcemia.
- Vitamin D · Concurrent use of large doses of vitamin D or its analogs may cause enhanced calcium absorption and induce hypercalcemia.
モニタリング
- Serum calcium (total and ionized)
- Serum magnesium, phosphate, and potassium
- Serum PTH (parathormone) if indicated
- Renal function tests
- ECG and heart rate (continuously during IV therapy)
- Urine calcium (if hypercalciuria develops)
過量投与
Oral overdoses of calcium-containing products are unlikely to cause hypercalcemia unless other drugs (e.g., Vitamin D) are given concurrently that enhance absorption. **Hypercalcemia** can occur with parenteral therapy or oral therapy combined with Vitamin D or increased PTH levels. * **Mild hypercalcemia:** Generally resolves without intervention when renal function is adequate. Withhold calcium therapy and Vitamin D analogs. * **Serious hypercalcemia (>12 mg/dL):** Treat by hydrating with IV normal saline and administering a loop diuretic (e.g., **furosemide**) to increase sodium and calcium excretion. Monitor and replace potassium and magnesium as necessary. Monitor ECG. Corticosteroids, calcitonin, and hemodialysis may also be employed.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。