パロキセチン
Paroxetine
Paroxetine HCl
別名: Paxil CR · Pexeva · Seroxat · BRL-29060 · FG-7051 · Paroxetine hydrochloride · Paroxetina · Paroxetinum
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 |
|---|---|---|---|---|---|
| Compulsive disorders | 1 mg/kg (up to 3 mg/kg) PO once daily (q24h) | PO | q24h | — | 🌎 NA |
| Generalized anxiety disorder | 1-1.5 mg/kg q24h | PO | q24h | — | 🌎 NA |
| Adjunctive treatment of phobias, fears, and anxieties | 0.5-1 mg/kg PO once daily | PO | q24h | — | 🌎 NA |
| Generalized anxiety and impulsivity | 1-2 mg/kg | PO | q24h | Long-term as needed | 🌍 EU |
- Generalized anxiety and impulsivity: Fluoxetine or clomipramine may be preferable due to authorized veterinary status.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| SSRI responsive behavior problems | 0.5-1 mg/kg q24h (2.5-5 mg per cat q24h) | PO | q24h | — | 🌎 NA |
| Compulsive disorders | 0.5-1 mg/kg PO once daily (q24h) | PO | q24h | — | 🌎 NA |
| Generalized anxiety disorder | 0.5-1.5 mg/kg q24h | PO | q24h | — | 🌎 NA |
| Marking | 0.5-1 mg/kg PO once daily | PO | q24h | — | 🌎 NA |
| Intercat aggression | 0.5-1 mg/kg PO once daily | PO | q24h | — | 🌎 NA |
| SSRI responsive behavior problems | 0.5-1.5 mg/kg PO q24-48h | PO | q24-48h | — | 🌎 NA |
| Urine marking (especially with overt aggression) | 0.5-1 mg/kg | PO | q24h | Long-term as needed | 🌍 EU |
- Urine marking (especially with overt aggression): Can be increased to 2 mg/kg PO q24h but close monitoring is required. Monitor urination frequency.
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
パロキセチンは強力な選択的セロトニン再取り込み阻害薬（SSRI）であり、獣医療においては主に行動修正のために適応外使用されます。フルオキセチンと構造的に関連していますが、異なる薬物動態および薬力学的特性を持っています。
- 犬：攻撃性、常同行動、強迫性障害（OCD）、全般性不安障害の治療に使用されます。
- 猫：尿スプレー（マーキング）、猫同士の攻撃行動、不安に関連する睡眠障害の管理に有効です。
臨床のポイント：フルオキセチンと比較して、パロキセチンは半減期が短く活性代謝物を持たないため、副作用が生じた場合のウォッシュアウト期間が短くて済みます。ただし、軽度の抗コリン作用を持つため、特に猫において便秘がより一般的な副作用となります。
作用機序
Paroxetine acts by selectively blocking the serotonin transporter (SERT) on the presynaptic neuronal membrane in the central nervous system.
- Inhibition of SERT → Decreased reuptake of serotonin (5-HT) from the synaptic cleft → Increased concentration and prolonged activity of 5-HT at postsynaptic 5-HT receptors.
- This potentiation of serotonergic neurotransmission helps regulate mood, anxiety, and compulsive behaviors.
- Paroxetine has minimal affinity for dopamine or norepinephrine receptors, but does exhibit mild affinity for muscarinic acetylcholine receptors, contributing to its anticholinergic side effect profile.
安全性・警告
禁忌
- Patients with known hypersensitivity to paroxetine
- Patients receiving monoamine oxidase inhibitors (MAOIs)
- Known hypersensitivity to paroxetine or other SSRIs
- History of seizures or epilepsy
- Concurrent use of Monoamine Oxidase Inhibitors (MAOIs)
- Concurrent use of other serotonergic agents (due to serotonin syndrome risk)
有害事象
- Anorexia (common, usually transient)
- Lethargy
- GI effects
- Irritability
- Insomnia/hyperactivity
- Panting
- Aggressive behavior in previously unaggressive dogs
- Constipation (especially in cats)
- Changes in elimination patterns
- Changes in blood glucose levels
- Reduced seizure threshold
- Decreased appetite
- Vomiting
- Trembling
- Restlessness
- Gastrointestinal disturbance
- Paradoxical increase in anxiety
- Potential increase in aggression
- Changes in urination frequency (cats)
注意事項
Use with caution in patients with seizure disorders, or severe cardiac, hepatic, or renal disease. Dosages may need to be reduced in patients with severe hepatic or renal impairment.
If paroxetine is rapidly discontinued, withdrawal reactions can occur. If the patient has been receiving the drug for an extended period, a gradual withdrawal is recommended. Safety during pregnancy has not been established (FDA Category C in humans); use caution in nursing patients as the drug is excreted into milk at low levels.
医薬品相互作用
Increased risk for serotonin syndrome
May increase paroxetine levels
May decrease or reverse the effects of SSRIs
Paroxetine (in humans) can decrease digoxin AUC by 15%
May alter insulin requirements
Increased risk for serotonin syndrome
High risk for serotonin syndrome; use contraindicated. A 5-week washout period is required after discontinuing paroxetine, and a 2-week washout if discontinuing the MAOI first.
Serotonin syndrome-like adverse effects possible
May decrease paroxetine levels
Increased plasma levels of phenytoin possible; may decrease paroxetine levels
Paroxetine may increase these beta-blockers' plasma levels and cause hypotension; atenolol may be safer
SSRIs can inhibit the metabolism of tramadol to active metabolites, decreasing efficacy and increasing toxicity risk (serotonin syndrome, seizures)
Paroxetine may increase TCA blood levels and may increase the risk for serotonin syndrome
Increased plasma levels of theophylline possible
Paroxetine may increase the risk for bleeding
High risk of fatal serotonin syndrome. Do not use paroxetine within 2 weeks of an MAOI, and do not use an MAOI within 6 weeks of stopping paroxetine.
Paroxetine antagonizes the effects of anticonvulsants and lowers the seizure threshold.
May lower seizure threshold and increase risk of adverse neurological events.
Increased risk of bleeding in the case of tissue trauma.
Increased risk of bleeding.
Increased risk of serotonin syndrome. Use only in exceptional cases with careful monitoring.
監視
- Efficacy of behavioral modification
- Adverse effects (including appetite and weight changes)
- Behavioral changes (efficacy, paradoxical anxiety, or increased aggression)
- Frequency of urination (especially in cats)
- Signs of serotonin syndrome (tremors, agitation, hyperthermia)
- Gastrointestinal tolerance (appetite, vomiting)
薬物動態
半減期
吸収
No veterinary data located. In humans, slowly but nearly completely absorbed from the GI tract. High first-pass effect means relatively small amounts reach systemic circulation unchanged. Food does not impair absorption.
分布
About 95% bound to plasma proteins.
代謝
Extensively metabolized, probably in the liver.
消失
Excreted primarily in urine as metabolites, with some fecal excretion.
過剰投与
Experience with overdoses in humans yields a mixed picture; while not as toxic as tricyclic antidepressants, fatalities and significant morbidity have occurred.
- Clinical Signs: ASPCA APCC data (2008-2009) reported common findings in dogs including hyperactivity, lethargy, mydriasis, and trembling. In cats, mydriasis was commonly noted.
- Treatment: In small animal overdoses, err on the safe side. Employ gut evacuation (if not contraindicated) followed by supportive care. Activated charcoal is very effective in binding paroxetine.
- Serotonin Syndrome: If serotonin syndrome develops, phenothiazines and cyproheptadine can be effective for control. Contact an animal poison control center for additional guidance.
製品
製剤
- Controlled-release oral tablets
- Oral suspension
- 20 mg oral tablet
- 30 mg oral tablet
- 2 mg/ml oral liquid suspension
ヒト用医薬品
- Paroxetine Oral Tablets: 10 mg, 20 mg, 30 mg & 40 mg; Paxil® (GlaxoSmithKline); Pexeva® (Synthon); generic; (Rx)
- Paroxetine Oral Tablets Controlled-release: 12.5 mg, 25 mg & 37.5 mg; Paxil® CR (GlaxoSmithKline); generic; (Rx)
- Paroxetine Oral Suspension: 2 mg/mL in 250 mL; Paxil® (GlaxoSmithKline); generic; (Rx)
- Paxil 20 mg, 30 mg tablets
- Seroxat 20 mg, 30 mg tablets
- Seroxat 2 mg/ml oral suspension
規制ステータス
POM (Prescription Only Medicine). Used under the prescribing cascade.
POM (Prescription Only Medicine). Used under the prescribing cascade.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Paroxetine oral tablets should be stored at 15-30°C. The oral suspension should be stored below 25°C.
飼主向け情報
- 忍耐が鍵です：パロキセチンのような行動治療薬は、十分な効果が現れるまでに数週間（通常4〜8週間）かかることがあります。獣医師の指示がない限り、急に投薬を中止しないでください。
- 投薬方法：食事と一緒でも、空腹時でも与えることができます。ペットが胃腸の不調を示した場合は、少量のおやつや食事と一緒に与えると良いでしょう。
- 副作用：食欲の変化（初期の食欲低下は一般的です）、無気力、または胃腸の不調に注意してください。猫の場合は、便秘やトイレの習慣の変化に注意して観察してください。
- 安全性：薬は子供や他のペットの手の届かないところに厳重に保管してください。用量が大きく異なるため、獣医師の承認なしに人間用の薬をペットに絶対に与えないでください。
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