ロラゼパム
Lorazepam
7-chloro-5-(2-chlorophenyl)-3-hydroxy-1,3-dihydro-2H-1,4-benzodiazepin-2-one
別名: Ativan · Lorazepam Intensol · BRN-07599084 · CB-8133 · Ro-7-8408 · Wy-4036 · lorazapamum · anxiedin · azurogen · bonatranquan · delormetazepam · lorazin · lorazon · lorenin · norlormetazepam · novhepar · novolorazem · oChloroxazepam · sinestron · Lorazepamum
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
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。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Status epilepticus (alternative to diazepam) | 0.2 mg/kg IV, IM or intranasal once | IV/IM/intranasal | once | — | 🌎 NA |
| Status epilepticus | 0.2 mg/kg IV once, followed by a bolus IV loading dose of levetiracetam at 60 mg/kg | IV | once | — | 🌎 NA |
| Fears, anxieties, phobias | 0.02-0.1 mg/kg PO once daily to three times a day | PO | q8-24h | — | 🌎 NA |
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Fears/anxiety | 0.02-0.5 mg/kg PO q8h | PO | q8h | — | 🌎 NA |
| Fears, anxieties, phobias, aversions | 0.02-0.1 mg/kg q8-24h | PO | q8-24h | — | 🌎 NA |
| Short-term management of anxiety disorders | 0.02-0.1 mg/kg | PO | q12-24h | Short-term | 🌍 EU |
- Fears, anxieties, phobias: May be used on an as needed basis
- Fears/anxiety: The lowest dose and frequency that alleviate the fear should be used
- Fears, anxieties, phobias, aversions: Minimally sedating, may require 4 weeks to peak effect
- Short-term management of anxiety disorders: Start at the lower end of the dose range and gradually increase as needed.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Fears/anxiety | 0.03-0.08 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| Fears, anxieties, phobias | 0.125 mg-0.25 mg total dose (¼-½ of a 0.5 mg tablet) once to twice a day | PO | q12-24h | — | 🌎 NA |
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Short-term management of anxiety disorders | 0.02-0.1 mg/kg | PO | q12-24h | Short-term | 🌍 EU |
- Fears/anxiety: The lowest dose and frequency that alleviate the fear should be used
- Fears, anxieties, phobias: May be used on an as needed basis
- Short-term management of anxiety disorders: Start at the lower end of the dose range and gradually increase. Monitor closely for signs of hepatotoxicity.
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
ロラゼパムは強力な中時間作用型ベンゾジアゼピン系薬であり、獣医療では主に行動障害に対する抗不安薬として、またてんかん重積状態の治療においてジアゼパムの代替薬として使用されます。
臨床のポイント： ジアゼパムとは異なり、ロラゼパムは活性代謝物を形成せずに直接グルクロン酸抱合を受けます。そのため、高齢、肥満、または肝機能障害のある患者にとってより安全な選択肢となります。
- 多様な投与経路： 経鼻、筋肉内、舌下/頬側など複数の経路で投与できるため、家庭やクリニックでの緊急のてんかん管理において非常に汎用性が高いです。
- 作用時間： ジアゼパムと同等の効果があると考えられており、抗てんかん作用の持続時間がより長い可能性があります（ただし、犬では明確に証明されていません）。
作用機序
Lorazepam acts as a positive allosteric modulator at the GABA-A receptor.
- It binds to the benzodiazepine site on the GABA-A receptor complex → enhances the affinity of the receptor for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA).
- This increases the frequency of chloride channel openings → influx of chloride ions → hyperpolarization of the neuronal membrane → decreased neuronal excitability.
- This widespread CNS depression primarily affects the subcortical levels (limbic, thalamic, and hypothalamic), yielding anxiolytic, sedative, skeletal muscle relaxant, and anticonvulsant effects.
- Other postulated mechanisms include antagonism of serotonin and diminished release or turnover of acetylcholine in the CNS.
安全性・警告
禁忌
- Hypersensitivity to benzodiazepines
- Severe respiratory insufficiency (unless mechanically ventilated)
- Glaucoma
- Significant liver disease
- Significant kidney disease
- Pregnant animals
- Lactating animals
有害事象
- Increased appetite
- Increased activity/excitement (paradoxical reaction)
- Vocalization
- Somnolence
- Lethargy
- Disinhibition (potential emergence of aggression)
- Drowsiness
- Mild transient incoordination (ataxia)
- Tremor and inappetence (associated with acute withdrawal)
注意事項
Withdrawal: When using for negative behaviors, withdraw the drug gradually to avoid a rebound effect. Physical dependency has been induced in dogs; long-term regular usage requires gradual weaning.
Administration Warning: Injectable lorazepam must NOT be given intra-arterially; arteriospasm may occur resulting in necrosis.
Pregnancy: Designated FDA Category D in humans (evidence of fetal risk), but animal studies suggest relative safety at usual dosages. High doses just prior to delivery can cause 'floppy infant' syndrome.
医薬品相互作用
Additive CNS effects
Decreased renal clearance of lorazepam
Increased CNS depression, irrational behavior
Decreased sedation from lorazepam
Increased lorazepam serum concentration
Inhibits the metabolism of lorazepam, potentially leading to increased plasma concentrations and prolonged sedation.
May inhibit the metabolism of lorazepam, increasing the risk of toxicity.
Additive CNS depression and sedation.
監視
- Clinical efficacy (seizure control or anxiety reduction)
- Adverse effects (CNS depression, paradoxical excitation, ataxia)
- Behavioral changes (watch for paradoxical aggression or extreme sedation)
- Liver enzymes (ALT, AST, ALP, Bilirubin), especially in cats
- Appetite and water intake
薬物動態
半減期
吸収
In humans, absolute bioavailability is ~90% orally. Rapidly and completely absorbed after IM dosing. Sublingual has similar bioavailability to oral, but peaks sooner. In dogs, intranasal administration reaches 30 ng/mL in 3-9 minutes.
分布
High affinity for benzodiazepine receptors in the CNS. Brain concentrations may persist longer than serum levels. Small amounts are distributed into milk.
代謝
Converted into inactive glucuronide forms in the liver in most species. Lack of active metabolites makes it safer for patients with liver dysfunction.
消失
Dogs: Primary elimination route is via urine. Cats: Elimination is ~50% in urine (primarily as glucuronide) and 50% in feces.
過剰投与
Overdoses of lorazepam are generally limited to CNS depression (confusion, lethargy, somnolence, decreased reflexes).
- Severe Toxicity: Very large overdoses can cause ataxia, hypotension, coma, and rarely death.
- Treatment: Standard protocols for removing/binding the drug in the gut (if orally ingested) and supportive systemic measures. Forced diuresis with IV fluids/electrolytes and mannitol may enhance excretion in patients with normal renal function.
- Antidote: Flumazenil may be considered for adjunctive treatment of serious overdoses, but it does not replace supportive therapy. Caution: Flumazenil is not recommended in patients with seizure disorders as it may induce seizures.
- Note: Analeptic agents (CNS stimulants like caffeine) are generally not recommended.
製品
製剤
- Concentrated Oral Solution
- Injection
- 1 mg oral tablets
- 2 mg/ml oral suspension
- 4 mg/ml injectable solution
ヒト用医薬品
- Lorazepam Tablets: 0.5 mg, 1 mg, & 2 mg
- Lorazepam Concentrated Oral Solution: 2 mg/mL
- Lorazepam Injection: 2 mg/mL & 4 mg/mL
- Ativan 1 mg tablets
- Intensol 2 mg/ml oral suspension
- Lorazepam 4 mg/ml injectable solution
規制ステータス
POM (Prescription Only Medicine). Subject to national controlled substance regulations.
POM-V / POM. Controlled Drug Schedule 4 Part 1.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Tablets should be stored in well-closed containers at room temperature (20-25°C). Oral solution and injection should be stored refrigerated (2-8°C) and protected from light. Injection must be diluted just prior to IV use with an equal volume of D5W, normal saline, or sterile water. Do not use if discolored or if a precipitate forms.
飼主向け情報
ロラゼパムは、ペットのてんかん発作のコントロールや、重度の不安や恐怖症の管理に使用される薬です。
- 食欲の変化： この薬はペットの食欲を増進させる可能性があります。望まない体重増加を防ぐため、厳密な食事制限が必要になる場合があります。
- 行動の変化： 活動レベルの変化に注意してください。眠気や無気力を引き起こすこともあれば、逆に活動の増加、興奮、鳴き声の増加を引き起こすこともあります。
- 急に服用を中止しない： 獣医師の指示なしに突然治療を中止しないでください。この薬を長期間定期的に服用している動物は、適切に「漸減」しないと離脱症状を起こす可能性があります。
- 肝臓の健康： ロラゼパムを服用している動物での肝毒性はまだ報告されていませんが、類似の薬（ジアゼパム）は猫にまれに肝毒性を引き起こすことがあります。嘔吐、食欲不振、白目や歯茎の黄疸に気づいた場合は、すぐに獣医師に連絡してください。
- 投薬のヒント： 錠剤は比較的無味で、唾液で容易に崩壊します。錠剤を飲ませるのが難しい場合は、患者の頬の内側に置き、1分ほどしてから小さなおやつを与えると飲み込みやすくなります。
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