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ドキセピン

Doxepin

Doxepin hydrochloride

三環系抗うつ薬 / 抗ヒスタミン薬POTopical犬猫鳥

別名: Sinequan · Anten · Aponal · Deptran · Desidoxepin · Doneurin · Doxal · Doxepia · Gilex · Mareen · Quitaxon · Triadapin · Zonalon · Sinepin · doxepini hydrochloridum · NSC-108160 · P3693A · Doxepinum · Doxepin hydrochloride

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

3-5 mg/kg PO q12h; maximum dose is 150 mg (per dog) q12hPO· q12h
— 🐕

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
Treatment of psychogenic dermatoses3-5 mg/kg PO q12h; maximum dose is 150 mg (per dog) q12hPOq12h—🌎 NA
Treatment of psychogenic dermatoses3-5 mg/kg, PO q8-12h. Begin at 3 mg/kg PO q12h for 2 weeks, then increase by 1 mg/kg PO q12h for 2 weeks up to the maximum dosage as needed; if no clinical response after at least 3-4 weeks of therapy, decrease dosage by 1 mg/kg PO q12h for 2 weeks until at the initial dosagePOq8-12hTitrated over weeks🌎 NA
Antihistaminic effects in treatment of atopy2.2 mg/kg PO three times dailyPOTID—🌎 NA
Antihistaminic effects in treatment of atopy3-5 mg/kg twice dailyPOBID—🌎 NA
Antihistaminic effects in treatment of atopy0.5-2 mg/kg PO q12hPOq12h—🌎 NA
Antihistaminic effects in treatment of atopy1-2 mg/kg PO q12hPOq12h—🌎 NA
Treatment of behavior problems (OCD)0.5-1 mg/kg PO twice dailyPOBID—🌎 NA
Treatment of behavior problems (acral lick granulomas)3-5 mg/kg PO q12h (up to 150 mg per dog)POq12h—🌎 NA
  • Antihistaminic effects in treatment of atopy: Used especially if dog has anxiety or other behavioral condition
  • Antihistaminic effects in treatment of atopy: May be best in nervous or highly strung dogs
  • Treatment of behavior problems (acral lick granulomas): Doses as above for psychogenic dermatoses

猫

適応用量経路頻度期間地域
Treatment of psychogenic dermatoses0.5-1 mg/kg PO q12-24h. Up to 25-50 mg (total dose) per cat.POq12-24hAllow 3-4 weeks for initial trial🌎 NA
Excessive grooming0.5-1 mg/kg PO q12h.POq12h—🌎 NA
Treatment of behavior problems (e.g., overgrooming, intercat aggression)0.5-1 mg/kg PO once to twice daily.POSID to BID—🌎 NA

鳥

適応用量経路頻度期間地域
Treatment of anxiety, pruritus caused feather plucking in psittacines1-2 mg/kg PO q12hPOq12h—🌎 NA
Treatment of anxiety, pruritus caused feather plucking in psittacines0.5-1 mg/kg PO twice dailyPOBID—🌎 NA

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。

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概要

ドキセピンはジベンゾオキサゼピン誘導体の​三環系抗うつ薬（TCA）​であり、獣医療では主に不安要素を伴う心因性皮膚疾患の補助療法として使用されます。

抗うつ薬に分類されますが、極めて強力な​H1-抗ヒスタミン作用​を持ち、そう痒と行動の問題を管理するための二重の目的を持つ薬剤です。アトピー性皮膚炎に対する単独の抗ヒスタミン薬としての有効性には議論がありますが、そう痒が不安や強迫行動（肢端舐性皮膚炎、過剰なグルーミングなど）を悪化させる、あるいは引き起こす場合には非常に有用です。

​臨床のポイント​: 抗不安作用と抗ヒスタミン作用を併せ持つため、アレルギー性皮膚疾患を患う神経質または興奮しやすい患者にしばしば選択されます。

作用機序

Doxepin exerts its effects through multiple receptor pathways:

  • ​Monoamine Reuptake Inhibition:​ In the central nervous system, doxepin blocks the presynaptic reuptake of norepinephrine (moderate inhibition) and ​serotonin (5-HT)​ (weak inhibition) → increasing their synaptic concentrations and prolonging their activity, which contributes to its antidepressant and anxiolytic effects.
  • ​Receptor Antagonism:​ It exhibits potent H1-histamine receptor blockade (providing anti-pruritic and sedative effects), as well as ​anticholinergic (muscarinic)​ and alpha-1 adrenergic blocking activity. These latter receptor affinities are largely responsible for its side effect profile (e.g., dry mouth, urinary retention, hypotension).

安全性・警告

禁忌

  • Prior sensitivity to doxepin or other tricyclic antidepressants
  • Concomitant use with Monoamine Oxidase Inhibitors (MAOIs) such as selegiline or amitraz (within 14 days)
  • Urinary retention
  • Glaucoma
  • Severe cardiac disease
  • History of seizures
  • Concurrent use with MAOIs

有害事象

  • Hyperexcitability (paradoxical)
  • Gastrointestinal distress
  • Lethargy and sedation
  • Ventricular arrhythmias (particularly in overdose)
  • Anticholinergic effects (dry mouth, urinary retention, constipation)
  • Altered blood glucose levels
  • Dry mouth (xerostomia)
  • Tachycardia

注意事項

​Pregnancy & Nursing:​ Safety during pregnancy has not been established (FDA Category C). Doxepin and its active metabolite distribute into milk; use with caution in nursing patients as sedation and respiratory depression have been reported in human infants.

​Cardiac Effects:​ Tricyclics can widen QRS complexes, prolong PR intervals, and invert or flatten T-waves on ECG. Use with caution in patients with pre-existing cardiac disease.

​Laboratory Alterations:​ May alter (increase or decrease) blood glucose levels.

医薬品相互作用

Anticholinergic AgentsModerate

Additive anticholinergic effects; use cautiously.

CimetidineModerate

May inhibit tricyclic antidepressant metabolism and increase the risk of toxicity.

CNS DepressantsModerate

Additive CNS depression; use cautiously.

Meperidine, Pentazocine, Dextromethorphan

Increased risk for serotonin syndrome.

Monoamine Oxidase Inhibitors (MAOIs, e.g., amitraz, selegiline)

Concomitant use (within 14 days) is generally contraindicated due to high risk of serotonin syndrome.

Quinidine

Increased risk for QTc interval prolongation and tricyclic adverse effects.

SSRIs (e.g., fluoxetine, paroxetine, sertraline)

Increased risk for serotonin syndrome.

Sympathomimetic Agents

May increase the risk of cardiac effects (arrhythmias, hypertension, hyperpyrexia).

Monoamine Oxidase Inhibitors (MAOIs)Major

Risk of fatal serotonin syndrome

Selective Serotonin Reuptake Inhibitors (SSRIs)Major

Increased risk of serotonin syndrome

監視

  • Efficacy (reduction in pruritus, anxiety, or compulsive behaviors)
  • Adverse effects (GI distress, lethargy, hyperexcitability)
  • ECG (if arrhythmias are suspected or in cases of overdose)
  • Heart rate and rhythm
  • Resolution of pruritus or behavioral signs
  • Signs of excessive sedation or anticholinergic effects

薬物動態

半減期

猫Variable犬Variable

吸収

Appears to be well absorbed after oral administration.

分布

Doxepin and its N-demethylated active metabolite are distributed into milk.

代謝

Extensively metabolized in the liver to an active N-demethylated metabolite.

消失

Excreted primarily via the kidneys as metabolites.

過剰投与

Overdosage with tricyclic antidepressants can be life-threatening.

  • ​Clinical Signs:​ Severe ventricular arrhythmias, cardiorespiratory collapse, profound CNS depression or seizures.
  • ​Action:​ Because the toxicities and therapies for treatment are complicated and controversial, it is highly recommended to contact an animal poison control center immediately for further information in any potential overdose situation.

製品

製剤

  • Capsules: 10 mg, 25 mg, 50 mg, 75 mg, 100 mg, 150 mg
  • Oral Concentrate: 10 mg/mL
  • Oral capsule (25 mg, 50 mg)
  • Topical cream

ヒト用医薬品

  • Doxepin Capsules: 10 mg, 25 mg, 50 mg, 75 mg, 100 mg & 150 mg (Sinequan, generic)
  • Doxepin Oral Concentrate: 10 mg/mL in 120 mL (generic)
  • Sinepin capsules (25 mg, 50 mg)
  • Sinequan capsules
  • Zonalon cream

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

POM (Prescription Only Medicine) status.

United Kingdom✓ 承認済み処方箋医薬品VMD

POM (Prescription Only Medicine) status.

規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

保管・安定性

Store protected from direct sunlight in tight, light-resistant containers at room temperature.

飼主向け情報

  • ​効果の発現​：行動や皮膚の改善が見られるまでに数週間（通常3〜4週間）かかる場合があります。処方通りに投薬を続けてください。
  • ​安全第一​：すべての三環系抗うつ薬は子供が開けにくい容器に入れ、子供やペットの手の届かない場所に保管してください。過剰摂取は致命的になる可能性があります。
  • ​急な休薬は避ける​：離脱症状を防ぐため、投薬を中止する前に獣医師に相談してください。
  • ​副作用の観察​：ペットが極度の無気力、予期せぬ多動、嘔吐、または頻脈/不整脈の兆候を示した場合は、獣医師に連絡してください。

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