ミルタザピン
Mirtazapine
6-azamianserin, Org-3770, mepirzapine
別名: Remeron SolTab · Zispin · Mirataz · 6-azamianserin · Org-3770 · mepirzapine · Mirtazapinum
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
監査済み v13 用量エビデンス
構造化された用量計算エビデンスChemotherapy-induced anorexia
- q24-72h
NA
必ず考慮する臨床コンテキスト (2)
- Management of weight loss (label dosage; FDA-approved): Using the transdermal formulation, apply 1.5-inch ribbon (≈2 mg/cat) to the inner pinna of the cat’s ear every 24 hours for 14 days. 1 The person applying medication should wear gloves. Alternate application of ointment between the left and right inner pinnae of the ears.
- ■ This medicine may be given with or without food. If your animal vomits after receiving the medication on an empty stomach, give it with food or a small treat. If vomiting continues, contact your veterinarian.
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
ミルタザピンは非定型四環系抗うつ薬であり、獣医療においては主に犬や猫の強力な食欲増進剤および制吐薬として広く使用されています。
- 臨床上のポイント: 慢性腎臓病（CKD）、うっ血性心不全、消化器疾患、肝疾患、または腫瘍の患者に特に有益であり、吐き気と食欲不振の両方を改善します。
- 難治性の嘔吐や化学療法誘発性の悪心・嘔吐（CINV）に対して、他の制吐薬と安全に併用できます。
- 主な用量制限となる副作用は鎮静ですが、猫では逆説的な興奮（鳴き声の増加、甘えん坊になるなど）が頻繁に観察されます。
重要: 鎮静作用を最小限に抑えるため、常に最低有効量を使用してください。犬では1日30mgを超えないようにしてください。高用量では逆説的に食欲増進効果が失われます。
作用機序
Mirtazapine has a complex, multi-receptor pharmacological profile (often classified as a NaSSA - Noradrenergic and Specific Serotonergic Antidepressant):
- Central pre-synaptic α2-adrenergic receptors: Antagonism blocks the negative feedback loop → increases Norepinephrine (NE) release → stimulates appetite via other α-receptors.
- 5-HT3 receptors: Potent antagonism in the Chemoreceptor Trigger Zone (CRTZ) and GI tract → provides robust anti-nausea and antiemetic effects.
- 5-HT2 receptors: Antagonism contributes to its anxiolytic profile.
- H1 (Histamine) receptors: Potent antagonism → produces prominent sedative effects.
- Peripheral α1-adrenergic & Muscarinic receptors: Moderate antagonism → may cause occasional orthostatic hypotension and mild anticholinergic effects.
安全性・警告
禁忌
- Hypersensitivity to mirtazapine
- Use of monoamine oxidase inhibitors (MAOIs, e.g., selegiline) within the past 14 days
- Pre-existing haematological disease
有害事象
- Drowsiness/sedation
- Increased affection (cats)
- Hypotension
- Tachycardia
- Sedation (common and can be profound)
- Increased vocalization (especially in cats)
- Altered behavior and increased interaction with others
- Blood dyscrasias (reported in humans)
注意事項
Use with caution in patients with known cardiac disease or cerebrovascular disease that could be exacerbated by hypotension.
- Monitor patients with renal impairment, renal failure, or hepatic disease closely, as clearance may be reduced.
- Use with caution in patients with diabetes mellitus, as antidepressants may indirectly affect blood glucose concentrations.
- Due to weak anticholinergic activity, use vigilance in patients susceptible to these effects (e.g., urinary retention, prostatic hypertrophy, acute closed-angle glaucoma, increased intraocular pressure, GI obstruction, or ileus).
- May impair concentration and alertness in active animals.
- Use cautiously in patients with pre-existing hematological disease (leukopenia, neutropenia, thrombocytopenia), as it has been rarely associated with blood dyscrasias in humans.
医薬品相互作用
Mirtazapine may cause increases in blood pressure
Minimal effects on mirtazapine blood levels, but may cause additive impairment of motor skills
May cause increased serum concentrations of mirtazapine
Increased risk for serotonin syndrome
Increased risk for serotonin syndrome; MAO inhibitors considered contraindicated with mirtazapine
Increased risk for serotonin syndrome
Increased risk of serotonin syndrome
監視
- Increased appetite
- Decreased episodes of vomiting
- Weight gain
- Adverse effects (sedation, vocalization, tachycardia)
- Appetite and body weight
- Behavioral changes (sedation, vocalization)
- Complete blood count (due to human risk of blood dyscrasias)
- Hepatic and renal function parameters
薬物動態
半減期
吸収
Rapidly and completely absorbed following oral administration. Food has minimal effects on rate and extent of absorption. Oral bioavailability is about 20% for dogs and 50% for humans.
分布
Plasma protein binding is approximately 70-72% for dogs, mice, and rats.
代謝
Metabolized via multiple pathways including 8-hydroxylation, N-oxidation, and demethylation followed by conjugation. Cats have a limited capacity for glucuronidation, leading to less rapid clearance and requiring extended dosing intervals.
消失
Elimination occurs primarily via urine (75%) and feces (15%). Renal or hepatic impairment may reduce clearance.
過剰投与
Ingestion of upwards of 10-fold to 30-fold the therapeutic dose in humans exhibits minimal toxicity requiring no acute intervention other than observation.
Treatment: Despite the wide safety margin, standard overdose protocols (including the administration of activated charcoal) and monitoring are recommended in acute overdose situations.
製品
製剤
- Oral Tablets
- Orally Disintegrating Tablets (ODT)
- 15 mg tablets
- 15 mg/ml oral solution
- Transdermal formulation (named patient basis / authorized veterinary preparations)
動物用医薬品
- None
- Mirataz 20 mg/g transdermal ointment
ヒト用医薬品
- Mirtazapine Oral Tablets: 7.5 mg, 15 mg, 30 mg & 45 mg (Remeron, generic)
- Mirtazapine Orally Disintegrating Tablets: 15 mg, 30 mg & 45 mg (Remeron SolTab, generic)
- Zispin 15 mg tablets
- Zispin 15 mg/ml oral solution
規制ステータス
Mirataz transdermal ointment is authorized for cats.
Mirataz transdermal ointment is authorized for cats.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store coated and orally disintegrating tablets at 25°C (77°F) with excursions permitted to 15-30°C (59-86°F). Protect from light and moisture. Orally disintegrating tablets should be used immediately once removed from the blister pack.
飼主向け情報
- 投与方法: 処方された通りに正確に投与してください。食事の有無にかかわらず投与できます。
- 口腔内崩壊錠（ODT）: 溶けるタイプの錠剤を使用する場合は、手が完全に乾いていることを確認してください。ペットの舌の下に錠剤を置き、溶けるまで数秒間口を閉じたままにします。その後、すぐに水を与えてください。
- 期待される効果: 食欲の改善と嘔吐の減少が見られるはずです。
- 報告すべき副作用: 過度の眠気、重度の脱力感、心拍数の増加、または異常な行動に気づいた場合は、獣医師に連絡してください。
猫の飼い主様への注意: この薬を服用した後、猫が異常に鳴くようになったり、過度に甘えてきたりすることは非常によくあります。これは一般的に無害ですが、生活の支障になる場合は獣医師にお知らせください。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。