氟西汀
**氟西汀 (Fluoxetine)** 是一種廣泛使用的選擇性血清素再攝取抑制劑 (SSRI) 抗憂鬱藥，在獸醫學中用於治療犬貓的各種行為障礙。 在犬隻中，它已獲得 FDA 批准（商品名 Reconcile®），用於結合行為矯正計畫治療**分離焦慮症**。它也常被標示外用於攻擊行為、刻板行為（強迫症）和廣泛性焦慮。在貓咪中，常被處方用於不當排泄（尿液記號）、攻擊行為、焦慮和心因性脫毛/搔癢。 > **臨床要點：** 氟西汀通常需要 **4 到 8 週** 的顯著滯後時間才能觀察到完整的臨床療效。這是因為突觸後受體向下調節需要時間。必須建議飼主在初期保持耐心並按時給藥。
作用機制: Fluoxetine acts by selectively binding to and inhibiting the presynaptic **serotonin transporter (SERT)** in the central nervous system. * **Inhibition of Reuptake:** Blockade of SERT prevents the reuptake of serotonin (5-HT) into the presynaptic neuron. * **Increased Synaptic Serotonin:** This leads to an accumulation of serotonin in the synaptic cleft → prolonged activation of postsynaptic **5-HT receptors**. * **Receptor Downregulation:** Chronic elevation of synaptic serotonin eventually leads to the downregulation and desensitization of autoreceptors (e.g., 5-HT1A), which correlates with the onset of anxiolytic, anticompulsive, and anti-aggressive clinical effects. Fluoxetine has minimal affinity for other neurotransmitter receptors (such as dopamine, norepinephrine, histamine, or acetylcholine), which accounts for its relatively favorable side effect profile compared to tricyclic antidepressants (TCAs).
各物種劑量
- Adjunctive treatment of aggression · 0.5-1.5 mg/kg PO once daily · PO · q24h
- To help control urine marking or separation anxiety · 0.5-1 mg/kg (2.55 mg per cat) PO once daily · PO · q24h
- To control pruritus when other therapies have failed · 1-5 mg/cat PO once daily · PO · q24h · Assess therapy after 1-4 weeks. Taper off dose over 6-8 weeks. · Advise obtaining baseline lab work.
- Generalized anxiety disorder · 0.5-1.5 mg/kg PO once daily · PO · q24h
- Urine spraying, psychogenic alopecia, and aggression · 0.5-1.0 mg/kg · PO · q24h · Long-term as directed · Similar precautions for aggression apply as in dogs.
- Treatment of canine separation anxiety in conjunction with a behavior modification plan · 1-2 mg/kg PO once daily · PO · q24h
- Separation anxiety and noise aversions · 1-2 mg/kg PO once daily · PO · q24h · Continue until 2 months after satisfactory response, then discontinue gradually · Use with behavioral therapy. May use long-term. Some dogs require life-long treatment. May add a benzodiazepine during seasonal noise fears.
- Adjunctive pharmacological intervention for conflict-related aggression · 1-2 mg/kg PO once a day · PO · q24h · May take up to 4 weeks for efficacy.
- Compulsive disorders · 1-2 mg/kg PO once daily · PO · q24h
給藥途徑
禁忌症
- Known hypersensitivity to fluoxetine
- Concurrent use of Monoamine Oxidase Inhibitors (MAOIs), including selegiline and amitraz (found in some tick collars)
- Patients with epilepsy or a history of seizures
- Concurrent use with drugs that lower the seizure threshold (e.g., acepromazine, chlorpromazine)
- Known sensitivity to fluoxetine or other SSRIs
- History of seizures or epilepsy
不良反應
- Anorexia or decreased appetite (common, often transient)
- Lethargy or depression
- Gastrointestinal upset (vomiting, diarrhea)
- Anxiety, irritability, or restlessness
- Insomnia or hyperactivity
- Panting (dogs)
- Changes in elimination patterns (cats)
- Paradoxical aggressive behavior (in previously unaggressive animals)
- Seizures (rare but possible)
- Lethargy
- Decreased appetite
- Vomiting
- Weight loss
- Trembling
- Restlessness
- Gastrointestinal disturbances
藥物相互作用
- BUSPIRONE · Increased risk for serotonin syndrome
- CYPROHEPTADINE · May decrease or reverse the effects of SSRIs (acts as a serotonin antagonist)
- DIAZEPAM, ALPRAZOLAM · Fluoxetine may increase diazepam and alprazolam plasma levels
- DIURETICS · Increased risk for hyponatremia
- INSULIN · May alter insulin requirements (can alter blood glucose)
- ISONIAZID · Increased risk for serotonin syndrome
- MAO INHIBITORS (e.g., amitraz, selegiline) · High risk for serotonin syndrome; use contraindicated. A 5-week washout is required after stopping fluoxetine before starting an MAOI, and a 2-week washout if switching from an MAOI to fluoxetine.
- PENTAZOCINE · Serotonin syndrome-like adverse effects possible
- PHENYTOIN · Increased plasma levels of phenytoin possible
- PROPRANOLOL, METOPROLOL · Fluoxetine may increase these beta-blocker's plasma levels; atenolol may be safer to use
- TRAMADOL · SSRIs can inhibit the metabolism of tramadol to active metabolites, decreasing efficacy and increasing toxicity risk (serotonin syndrome, seizures)
- TRICYCLIC ANTIDEPRESSANTS (e.g., clomipramine, amitriptyline) · Fluoxetine may increase TCA blood levels and increase the risk for serotonin syndrome
監測
- Efficacy of the behavior modification plan and reduction of clinical signs
- Appetite and body weight (due to risk of anorexia)
- Signs of adverse effects (GI upset, lethargy, paradoxical aggression, seizures)
- Behavioral response and changes in aggression
- Appetite and body weight
- Signs of serotonin syndrome (tremors, agitation, hyperthermia)
- Gastrointestinal tolerance
過量
The LD50 for rats is 452 mg/kg. **Clinical Signs of Toxicity:** * **Dogs:** Vomiting, mydriasis (dilated pupils), lethargy, hyperactivity, and seizures. Seizures have been reported at doses twice the highest recommended human dose. * **Cats:** Hypersalivation, vomiting, mydriasis, and excessive vocalization. **Treatment:** * Treatment is symptomatic and supportive. * Gut emptying techniques (emesis, activated charcoal) should be employed if recent and not contraindicated (e.g., patient is seizing or comatose). * **Diazepam** is the treatment of choice for controlling seizures. * **Cyproheptadine** can be administered as a serotonin antagonist if serotonin syndrome is suspected.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。