伊米帕明
伊米帕明 (Imipramine) 是一種**三環類抗憂鬱藥 (TCA)**，在獸醫學中常作為仿單標示外使用。雖然主要用於行為問題（如分離焦慮），但其獨特的受體作用使其具有多種用途。 * 在**犬貓**中，常被用於治療**尿失禁**和**猝倒症 (cataplexy)**。 * 在**馬匹醫學**中，則用於控制**猝睡症 (narcolepsy)**及誘導藥理性射精。 > **臨床要點：**伊米帕明是一種三級胺 TCA，在肝臟中會迅速代謝為具活性的二級胺代謝物**去甲伊米帕明 (desipramine)**。這種雙重作用擴大了其藥理範圍，同時影響血清素和正腎上腺素途徑。
作用機制: Imipramine and its active metabolite, desipramine, exert their effects through a complex, multi-receptor pharmacologic profile: * **Monoamine Reuptake Inhibition**: Blocks the presynaptic amine pump, preventing the reuptake of **serotonin (5-HT)** and **norepinephrine (NE)** → increases neurotransmitter concentrations in the synaptic cleft → modulates mood, arousal, and pain pathways. * **Anticholinergic Activity**: Antagonizes **muscarinic receptors** centrally and peripherally. This mechanism is primarily responsible for its efficacy in treating urinary incontinence (facilitating urine storage by relaxing the detrusor muscle) and its common side effects (dry mouth, tachycardia). * **Alpha-Adrenergic Agonism/Antagonism**: Exhibits complex interactions at alpha receptors, which may contribute to increasing internal urethral sphincter tone. * **Antihistaminic (H1) Activity**: Contributes to its significant **sedative** properties.
各物種劑量
- Urethral incompetence · 2.5-5 mg (total dose) · PO · q12h
- Adjunctive cancer pain treatment · 2.5-5 mg (total dose) · PO · q12h
- Anxiety, inappropriate urination · 0.5-1 mg/kg · PO · q12-24h
- Pharmacologic induced ejaculation · 2 mg/kg · IV · once · If imipramine alone does not induce erection and ejaculation in 10-15 minutes, give xylazine 0.2-0.3 mg/kg IV. (Note: ARCI UCGFS Class 2 Drug)
- Narcolepsy/cataplexy · 0.55 mg/kg IV or 250-750 mg (total dose) orally · IV, PO · once · PO administration produces inconsistent results.
- Urethral incompetence · 5-15 mg (total dose) · PO · q12h
- Urinary incontinence when other agents fail · 5-20 mg (total dose) · PO · q12h
- Cataplexy · 0.5-1 mg/kg · PO · q8h · Titrate dose based on clinical effect
- Adjunctive treatment of separation anxiety or other tricyclic antidepressant-responsive behavior disorders · 2.2-4.4 mg/kg · PO · once to twice daily
- Adjunctive cancer pain treatment · 0.5-1 mg/kg · PO · q8h
給藥途徑
禁忌症
- Prior sensitivity to any tricyclic antidepressant
- Concomitant use with monoamine oxidase inhibitors (MAOIs) within 14 days
- Glaucoma
- History of seizures
- Urinary retention
- Severe liver disease
- Hypersensitivity to tricyclic antidepressants
不良反應
- Sedation
- Dry mouth
- Constipation
- Tachycardia
- Hyperexcitability
- Tremors
- Seizures (CNS stimulation)
- Bone marrow suppression
- Diarrhea
- Vomiting
- Diarrhoea
- Excitability
- Arrhythmias
- Hypotension
- Syncope
- Increased appetite
藥物相互作用
- Anticholinergic agents · Additive anticholinergic effects; use cautiously
- Cimetidine · May inhibit tricyclic antidepressant metabolism and increase the risk of toxicity · major
- CNS Depressants · Additive CNS depressant effects; use cautiously
- Levodopa · Imipramine may decrease levodopa oral absorption
- Phenobarbital · May decrease tricyclic levels
- Quinidine · Increased risk for QTc interval prolongation and tricyclic adverse effects
- Rifampin · May decrease tricyclic blood levels
- 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 (including amitraz, selegiline) · Concomitant use (within 14 days) is generally contraindicated due to risk of serotonin syndrome
- Thyroid agents · May increase risk for cardiac arrhythmias
- Cisapride · Increased risk for prolonged QT interval
- Clonidine · Tricyclics may increase blood pressure
監測
- Clinical efficacy
- Adverse effects
- ECG (Tricyclics can widen QRS complexes, prolong PR intervals, and invert or flatten T-waves)
- Blood Glucose (Tricyclics may increase or decrease blood glucose levels)
- Heart rate and rhythm (ECG) in susceptible patients
- Signs of serotonin syndrome (agitation, tremors, hyperthermia, tachycardia) if used with other serotonergic drugs
- Liver function tests (baseline and periodic)
過量
Overdosage with tricyclics can be **life-threatening**, leading to severe arrhythmias and cardiorespiratory collapse. Because the toxicities and therapies for treatment are complicated and controversial, it is highly recommended to **contact a poison control center** for further information in any potential overdose situation.
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