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アミトリプチリン

Amitriptyline

Amitriptyline hydrochloride

三環系抗うつ薬 (TCA) / 行動修飾薬 / 神経障害性疼痛緩和薬POParenteral犬猫鳥

別名: Elavil · Lentizol · Tryptanol · Amitriptylini hydrochloridum · Amitriptylinum · Amitriptyline 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

1-2 mg/kg PO 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
Adjunctive treatment of pruritus1-2 mg/kg PO q12hPOq12h—🌎 NA
Acral pruritic dermatitis2.2 mg/kg PO twice dailyPOq12h2-4 week trial recommended🌎 NA
Separation anxiety or generalized anxiety1-2 mg/kg PO q12hPOq12h—🌎 NA
Behavior disorders amenable to tricyclics1-4 mg/kg PO q12h. Begin at 1-2 mg/kg PO q12h for 2 weeks, increase by 1 mg/kg up to maximum dosage (4 mg/kg) as necessary. If no clinical response, decrease by 1 mg/kg PO q12h for 2 weeks until at initial dosage.POq12h—🌎 NA
Behavior disorders amenable to tricyclics2.2-4.4 mg/kg PO q12hPOq12h—🌎 NA
Behavior disorders amenable to tricyclics0.25-1.5 mg/kg PO every 12-24hPOq12-24h—🌎 NA
Neuropathic pain1-2 mg/kg PO q12-24hPOq12-24h—🌎 NA
Adjunctive treatment of pain associated with appendicular osteosarcoma1-2 mg/kg PO q12-24hPOq12-24h—🌎 NA
Management of chronic anxiety, compulsive disorders, and separation anxiety1-2 mg/kgPOq12-24h—🌍 EU
  • Acral pruritic dermatitis: Only occasionally effective.
  • Separation anxiety or generalized anxiety: Use with behavior modification.
  • Management of chronic anxiety, compulsive disorders, and separation anxiety: Clomipramine is an authorized preparation for dogs and is claimed to have better anticompulsive properties.

猫

適応用量経路頻度期間地域
Adjunctive treatment of behavior disorders amenable to tricyclics5-10 mg per cat PO once dailyPOq24h—🌎 NA
Adjunctive treatment of behavior disorders amenable to tricyclics0.5-2 mg/kg PO q12-24h; start at 0.5 mg/kg PO q12hPOq12-24h—🌎 NA
Adjunctive treatment of behavior disorders amenable to tricyclics0.5-1 mg/kg PO q12-24hPOq12-24h—🌎 NA
Adjunctive treatment of behavior disorders amenable to tricyclics0.5-1 mg/kg PO q12-24h. Allow 3-4 weeks for initial trial.POq12-24h3-4 weeks initial trial🌎 NA
Self-mutilation behaviors associated with anxiety5-10 mg per cat PO once to twice dailyPOq12-24h—🌎 NA
Self-mutilation behaviors associated with anxiety1-2 mg/kg PO q12hPOq12h—🌎 NA
Pruritus (after other more conventional therapies have failed)5-10 mg per cat PO once daily or 2.5-7.5 mg/cat once to twice daily. When discontinuing, taper dose over 1-3 weeks.POq12-24h—🌎 NA
Symptomatic therapy of idiopathic feline lower urinary tract disease (FLUTD)2.5-12.5 mg (total dose) PO once daily at nightPOq24h—🌎 NA
Symptomatic therapy of idiopathic feline lower urinary tract disease (FLUTD)5-10 mg (total dose) PO once daily at night; the drug is in popular use at present and further studies are neededPOq24h—🌎 NA
Symptomatic therapy of idiopathic feline lower urinary tract disease (FLUTD)2.5-12.5 mg (total dose) PO at the time the owner retires for the night. Dosage is adjusted to produce a barely perceptible calming effect on the cat. If no improvement is seen within 2 months, the medication may be gradually tapered and then stopped.POq24h2 months trial🌎 NA
Neuropathic pain2.5-12.5 mg/cat PO once dailyPOq24h—🌎 NA
Neuropathic pain0.5-2 mg/kg PO once daily; may be a useful addition to NSAIDs for chronic pain.POq24h—🌎 NA
Management of psychogenic alopecia, hypervocalization, and idiopathic cystitis0.5-1 mg/kgPOq24h—🌍 EU
  • Self-mutilation behaviors associated with anxiety: With behavior modification.
  • Pruritus (after other more conventional therapies have failed): Taper dose over 1-3 weeks when discontinuing.
  • Symptomatic therapy of idiopathic feline lower urinary tract disease (FLUTD): Reserved for cases with severe, recurrent signs.
  • Management of psychogenic alopecia, hypervocalization, and idiopathic cystitis: Very bitter taste; can cause ptyalism.

鳥

適応用量経路頻度期間地域
Adjunctive treatment of feather plucking1-2 mg/kg PO q12-24 hours. Anecdotal reports indicate some usefulness. Barring side-effects, may be worth a more prolonged course of therapy to determine efficacy.POq12-24hProlonged course🌎 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

アミトリプチリンは第一世代の​三環系抗うつ薬 (TCA)​です。犬の原発性行動障害（分離不安など）の治療においては、クロミプラミンやSSRI（フルオキセチンなど）のような新しい薬剤に取って代わられつつありますが、獣医療においては依然として非常に汎用性の高い薬剤です。

​臨床のポイント​: そのマルチモーダルな受容体活性により、​神経障害性疼痛​、​そう痒症​（強力な抗ヒスタミン作用による）、および​猫特発性下部尿路疾患 (FLUTD/FIC)​の補助治療に特に有用です。また、鳥類の毛引き行動を管理するために使用されることもあります。

作用機序

Amitriptyline and its active metabolite, nortriptyline, exhibit a complex pharmacologic profile, affecting multiple receptor systems:

  • Serotonin (SERT) & Norepinephrine (NET) Reuptake Inhibition: Blocks the amine pump → increases synaptic levels of 5-HT and NE → mood stabilization and descending pain pathway modulation.
  • H1-Receptor Antagonism: Potent antihistamine effect → stabilizes mast cells and provides antipruritic action.
  • M1-Muscarinic (Anticholinergic) Antagonism: Causes smooth muscle relaxation (useful in FLUTD) but also leads to side effects like dry mouth and urine retention.
  • Alpha-1 Adrenergic Antagonism: Can cause mild vasodilation and sedation.
  • NMDA Receptor & Sodium Channel Blockade: Contributes to its efficacy in treating chronic, neuropathic pain.

安全性・警告

禁忌

  • Prior sensitivity to any tricyclic antidepressant
  • Concomitant use with monoamine oxidase inhibitors (MAOIs)

有害事象

  • Sedation
  • Constipation
  • Urinary retention
  • Hyperexcitability (dogs)
  • Seizures (rare)
  • Cardiac dysrhythmias
  • Bone marrow suppression
  • Vomiting
  • Diarrhea
  • Hypersalivation (cats)
  • Anorexia (cats)
  • Thrombocytopenia
  • Neutropenia
  • Unkempt hair coat (cats)
  • Ataxia
  • Disorientation

注意事項

Use with extreme caution in patients with seizure disorders as tricyclic agents may reduce seizure thresholds. Use with caution in patients with thyroid disorders, hepatic disorders, keratoconjunctivitis sicca (KCS), glaucoma, cardiac rhythm disorders, diabetes, or adrenal tumors. FDA Pregnancy Category D (restrict use to pregnant animals only when benefits clearly outweigh risks).

医薬品相互作用

Anticholinergic agents

Increased effects; hyperthermia and ileus possible

CimetidineModerate

May inhibit tricyclic antidepressant metabolism and increase the risk of toxicity

Cisapride

May have additive effects on QTc interval; possible serious arrhythmias may result

Monoamine Oxidase Inhibitors (selegiline, amitraz)

Potential life-threatening serotonin syndrome; use together not recommended

CNS Depressants

Increased sedative effects

DiazepamModerate

Possible increased amitriptyline levels

Quinidine

Increased risk for QTc interval prolongation and tricyclic adverse effects

Selective-Serotonin Re-uptake Inhibitors (SSRIs, fluoxetine)

Potential increased amitriptyline levels, increased risk for serotonin syndrome; enhanced monitoring suggested if used together

Sympathomimetic agents

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

Thyroid agents

Increased risk for arrhythmias; monitor closely

Monoamine oxidase inhibitors (MAOIs)Major

Risk of fatal serotonin syndrome. Requires a minimum 2-week washout period.

ChlorphenamineModerate

Metabolized by CYP2D6; may alter amitriptyline metabolism.

ClomipramineMajor

Concurrent use increases the risk of serotonin syndrome.

FluoxetineMajor

Concurrent use increases the risk of serotonin syndrome.

TramadolMajor

Increased risk of serotonin syndrome and seizure threshold reduction.

監視

  • Clinical efficacy (behavior, pain, or pruritus improvement)
  • Adverse effects
  • Baseline cardiac evaluation (ECG) prior to therapy
  • Baseline CBC and serum chemistry panel prior to therapy
  • Liver enzymes in cats (prior to therapy, 1 month after initial therapy, and yearly thereafter)

薬物動態

半減期

犬6-8 hours

吸収

Rapidly absorbed from both the GI tract and parenteral injection sites. Transdermal (PLO-gel based) absorption in cats is poor. Peak levels occur in 1-2 hours after oral administration in cats and within 2-12 hours in other species.

分布

Highly bound to plasma proteins. Enters the CNS and enters maternal milk in levels at or greater than those found in maternal serum.

代謝

Metabolized in the liver to several metabolites, including the active metabolite nortriptyline.

消失

Eliminated primarily via hepatic metabolism.

過剰投与

Overdosage with tricyclics can be life-threatening (arrhythmias, cardiorespiratory collapse). Because toxicities and therapies are complicated, it is recommended to contact an animal poison control center immediately in any potential overdose situation.

  • Dogs: Common findings include lethargy and tachycardia.
  • Cats: Common findings include vocalization, ataxia, mydriasis (dilated pupils), tachycardia, disorientation, lethargy, and agitation.

製品

製剤

  • Tablets
  • Injection

ヒト用医薬品

  • Amitriptyline HCl Tablets: 10 mg, 25 mg, 50 mg, 75 mg, 100 mg, & 150 mg

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

POM (Prescription Only Medicine). Clomipramine is the authorized TCA for dogs in the EU.

United Kingdom✓ 承認済み処方箋医薬品VMD

POM-V. Prescribed under the cascade as human generic preparations.

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

保管・安定性

Tablets should be stored at room temperature. The injection should be kept from freezing and protected from light.

飼主向け情報

​忍耐が鍵です​: 行動の変化は一朝一夕には起こりません。十分な効果が現れるまでには、通常​数週間​の継続的な毎日の投薬が必要です。

  • ​急に服用を中止しないでください​: 投薬を中止する場合は、離脱症状を防ぐために獣医師の指導のもとでゆっくりと用量を減らす必要があります。
  • ​副作用​: ペットが眠そうにしたり、口が渇いたりする（唇を舐める回数が増えるなど）ことがあります。便秘や排尿困難が起こることもあるため、これらの兆候が見られた場合は獣医師に連絡してください。
  • ​毒性の警告​: 子供や他のペットの手の届かない、子供が開けにくい容器に厳重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。
  • ​投薬方法​: 錠剤は苦みがある場合があります。嗜好性の高いおやつやピルポケットに隠して与えることをお勧めします。

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。