クロナゼパム
Clonazepam
5-(2-chlorophenyl)-7-nitro-1,3-dihydro-1,4-benzodiazepin-2-one
別名: Klonopin · Antelepsin · Clonagin · Clonapam · Clonax · Clonex · Diocam · Epitril · Iktorivil · Kenoket · Kriadex · Neuryl · Paxam · Rivatril · Rivotril · Solfidin · Linotril · clonazepamum · Ro-5-4023
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 |
|---|---|---|---|---|---|
| Adjunctive medication in the treatment of seizures | 1-2 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| Adjunctive medication in the treatment of seizures | 0.5 mg/kg PO two to three times a day | PO | q8-12h | — | 🌎 NA |
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Anxiolytic | 0.1-1 mg/kg PO two to three times a day | PO | q8-12h | — | 🌎 NA |
| Muscular hypertonicity (episodic falling) / Anxiolytic | 0.5 mg/kg | PO | q8-12h | — | 🌍 EU |
- Adjunctive medication in the treatment of seizures: May need to lower phenobarbital dose by 10-20%
- Muscular hypertonicity (episodic falling) / Anxiolytic: Suggested starting dose but there is a wide range of recommendations.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Anxiolytic | 0.02-0.2 mg/kg PO once to two times a day | PO | q12-24h | — | 🌎 NA |
| Anxiolytic | 0.1-0.2 mg/kg PO as needed or up to two times a day | PO | PRN or q12h | — | 🌎 NA |
| Adjunctive medication in the treatment of seizures | Starting dose is 0.5 mg (total dose) PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Adjunctive medication in the treatment of seizures | 1/8th to 1/4 of a 0.5 mg tablet PO two to three times daily | PO | q8-12h | — | 🌎 NA |
| Anxiolytic / Hyperaesthesia / Epilepsy | 0.5 mg/cat | PO | q12-24h | — | 🌍 EU |
- Adjunctive medication in the treatment of seizures: Anecdotally more effective for maintenance and to decrease cluster seizures; acute hepatic necrosis possible
- Anxiolytic / Hyperaesthesia / Epilepsy: Suggested starting dose but there is a wide range of recommendations.
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
クロナゼパムは強力で長時間作用型のベンゾジアゼピン系薬物であり、獣医療では主に補助的な抗てんかん薬および抗不安薬として使用されます。
臨床上のポイント: 犬では、抗てんかん効果に対する耐性が急速に（通常1〜4週間以内に）発現するため、長期的な維持抗てんかん薬としての有用性は非常に限られています。これは受容体のダウンレギュレーションと薬物動態の変化によるものです。したがって、短期間のパルス療法や群発発作の管理にはるかに適しています。
- 猫では、てんかんや不安の長期的な補助治療に使用できます。猫における経口ベンゾジアゼピン系薬物（特にジアゼパム）は特異体質性の急性肝壊死を引き起こすリスクが知られていますが、クロナゼパムではその可能性は低いと考えられています。ただし、モニタリングは依然として必要です。
- クロナゼパムは、ヒトにおける乱用および依存の可能性があるため、スケジュールIV（C-IV）の規制薬物に指定されています。
作用機序
Clonazepam acts as a positive allosteric modulator at the GABA-A receptor complex in the central nervous system.
- It binds to specific benzodiazepine receptors (located primarily in the limbic, thalamic, and hypothalamic regions) → enhances the affinity of the receptor for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA).
- This increases the frequency of chloride channel opening → influx of chloride ions → cellular hyperpolarization → decreased neuronal excitability.
- Additional 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 clonazepam or other benzodiazepines
- Significant liver disease or dysfunction
- Acute narrow-angle glaucoma
- Myasthenia gravis (may exacerbate weakness)
- Marked CNS depression
- Respiratory depression
- Severe muscle weakness
- Hepatic impairment (may worsen hepatic encephalopathy)
有害事象
- Sedation and lethargy
- Ataxia (incoordination)
- Paradoxical excitement, hyperactivity, or vocalization
- Increased salivation
- Gastrointestinal upset (vomiting, diarrhea, constipation)
- Dogs: Rapid tolerance to anticonvulsant effects
- Cats: Polyphagia, potential for acute hepatic necrosis (rare)
- Respiratory suppression (at higher doses)
- Acute hepatic necrosis (idiosyncratic in cats)
- Tolerance development
注意事項
Do not discontinue therapy abruptly, especially in patients on chronic or high-dose therapy, as this may precipitate withdrawal signs or status epilepticus; taper the dose gradually. Use with caution in nursing dams, as benzodiazepines can enter milk and accumulate to toxic levels in neonates. Monitor cats closely for signs of hepatotoxicity.
医薬品相互作用
May increase clonazepam levels by inhibiting its metabolism.
May decrease the metabolism of benzodiazepines, increasing their effects.
Additive CNS depression; may cause profound sedation or respiratory depression.
May decrease the metabolism of benzodiazepines.
May decrease clonazepam concentrations via hepatic enzyme induction.
May decrease clonazepam concentrations.
May decrease clonazepam concentrations.
May induce hepatic microsomal enzymes and decrease the pharmacologic effects of benzodiazepines.
Inhibition of CYP450 enzymes may decrease clonazepam clearance, increasing its plasma levels and risk of toxicity.
Additive sedation and respiratory depression.
監視
- Clinical efficacy (seizure frequency, anxiety levels)
- Adverse effects (sedation, ataxia, paradoxical excitement)
- Therapeutic blood levels (reported target: 0.015-0.07 mcg/mL)
- Cats: Baseline and periodic liver function tests
- Degree of sedation and ataxia
- Respiratory rate and effort
- Hepatic function panel (especially in cats)
- Clinical response (seizure frequency, muscle tone, or behavioral changes)
薬物動態
半減期
吸収
In dogs, oral bioavailability is variable (20-60%) but absorption is rapid. In humans, it is well absorbed from the GI tract with peak serum levels occurring about 3 hours after oral dosing.
分布
Highly lipophilic; rapidly crosses the blood-brain barrier and placenta. Protein binding in dogs is approximately 82%.
代謝
Metabolized in the liver to several metabolites. In dogs, clonazepam exhibits saturation kinetics, meaning elimination rates are dose-dependent.
消失
Metabolites are excreted primarily in the urine.
過剰投与
Overdoses commonly cause profound sedation, depression, and ataxia.
- Paradoxical Reactions: Some animals may exhibit paradoxical signs such as hyperactivity, disorientation, agitation, and vocalization. Paradoxical excitation can be treated with a mild sedative, such as diphenhydramine.
- Management: Emesis is generally NOT indicated due to the risk of rapid CNS depression and aspiration. Mild to moderate overdoses can often be monitored at home if the animal is rousable and not showing paradoxical signs. Keep the animal confined and minimize stimulation.
- Severe Toxicity: Massive overdoses can lead to respiratory depression or hypotension. Flumazenil (a specific benzodiazepine antagonist) can be used to reverse severe respiratory or CNS depression. Because flumazenil has a short half-life, multiple doses may be required.
製品
製剤
- Oral tablets
- Orally disintegrating tablets (ODT)
- Compounded oral suspension
- 0.25 mg tablet
- 0.5 mg tablet
- 1.0 mg tablet
- 2 mg tablet
- 500 mcg tablet
- 500 mcg/5 ml oral solution
- 2 mg/5 ml oral solution
ヒト用医薬品
- Clonazepam Oral Tablets: 0.5 mg, 1 mg, & 2 mg (Klonopin, generic)
- Clonazepam Orally Disintegrating Tablets: 0.125 mg, 0.25 mg, 0.5 mg, 1 mg & 2 mg (Klonopin Wafers, generic)
- Linotril
- Rivotril
規制ステータス
POM (Prescription Only Medicine). Subject to national controlled drug regulations.
POM. Prescriptions are subject to controlled drug requirements.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Tablets should be stored in airtight, light-resistant containers at room temperature. Compounded oral suspensions (0.1 mg/mL in Ora-Plus/Ora-Sweet) retain >90% potency for 60 days when stored at 5°C or 25°C, but must be protected from light.
飼主向け情報
- 規則正しい投薬が重要: 抗てんかん治療が失敗する主な要因は、処方通りの投薬が行われないことです。決められた時間に規則正しく薬を与えることが非常に重要です。
- 急に投薬を中止しないこと: 獣医師の指示なしに、この薬を突然中止しないでください。急な離脱は、重度で生命を脅かす持続的なてんかん発作（てんかん重積状態）を引き起こす可能性があります。投薬を中止する必要がある場合は、獣医師が徐々に減量するスケジュールを指示します。
- 副作用: 投薬開始時には軽度の眠気やふらつきがよく見られますが、通常は改善します。ペットが異常に活動的になったり興奮したりした場合は、獣医師に連絡してください。
- 猫の飼い主様へ: 猫の食欲不振、嘔吐、または白目や歯茎の黄ばみ（黄疸）がないか注意深く観察してください。これらは稀ですが重篤な肝臓の問題の兆候である可能性があります。これらの兆候に気づいた場合は、直ちに獣医師に連絡してください。
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