Imipramine
Imipramine is a **tricyclic antidepressant (TCA)** used off-label in veterinary medicine. While primarily recognized for its behavioral applications (such as separation anxiety), its unique receptor profile makes it highly versatile. * In **dogs and cats**, it is frequently utilized for **urinary incontinence** (urethral incompetence) and **cataplexy**. * In **equine medicine**, it is employed to manage **narcolepsy** and to induce pharmacologic ejaculation. > **Clinical Pearl:** Imipramine is a tertiary amine TCA that is rapidly metabolized in the liver into its active secondary amine metabolite, **desipramine**. This dual-action broadens its pharmacologic spectrum, affecting both serotonin and norepinephrine pathways.
กลไกการออกฤทธิ์: 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.
ขนาดยาตามชนิดสัตว์
- 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
วิธีการให้ยา
ข้อห้ามใช้
- 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
อาการไม่พึงประสงค์
- Sedation
- Dry mouth
- Constipation
- Tachycardia
- Hyperexcitability
- Tremors
- Seizures (CNS stimulation)
- Bone marrow suppression
- Diarrhea
- Vomiting
- Diarrhoea
- Excitability
- Arrhythmias
- Hypotension
- Syncope
- Increased appetite
อันตรกิริยาระหว่างยา
- 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
การติดตาม
- 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)
การได้รับยาเกินขนาด
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.
ข้อมูลอ้างอิงยาของ VetSheet มีไว้สำหรับสัตวแพทย์ผู้มีใบอนุญาตเพื่อช่วยในการตัดสินใจทางคลินิก ไม่ใช่สิ่งทดแทนการวินิจฉัยของผู้เชี่ยวชาญหรือฉลากล่าสุดของผู้ผลิต