トラゾドン
トラゾドンは**セロトニン2A拮抗薬/再取り込み阻害薬 (SARI)**であり、獣医療において抗不安薬および軽度の鎮静薬として広く使用されています。 - **臨床的有用性**: 状況的不安（雷雨、花火、動物病院への受診、旅行など）や、術後の運動制限・ケージレストの補助に非常に有効です。 - **補助療法**: 難治性の行動障害に対して、SSRI（フルオキセチンなど）やガバペンチンと併用されることがよくあります。 - **安全性**: 一般的に忍容性が高く、安全域が広いです。三環系抗うつ薬（TCA）と比較して抗コリン作用が少なく、発作のリスクも低いです。 - **ヒトでの用途**: うつ病、攻撃的行動、アルコールやコカインの離脱症状、片頭痛の予防、不眠症の治療に使用されます。
作用機序: Trazodone exerts its anxiolytic and sedative effects through multiple neurochemical pathways: - **Serotonin Reuptake Inhibition**: Blocks the serotonin transporter (SERT) → increases extracellular serotonin (5-HT) in the synaptic cleft. - **5-HT2A Receptor Antagonism**: Blocks 5-HT2A receptors → prevents overstimulation by serotonin, contributing to its anxiolytic and antidepressant efficacy. Downregulation of these receptors can augment the efficacy of concurrent SSRIs. - **Active Metabolite**: Hepatic metabolism produces **m-chlorophenylpiperazine (mCPP)**, which acts as a direct, non-selective serotonin receptor agonist. - **Alpha-1 Adrenergic Antagonism**: Blocks peripheral alpha-1 receptors → can cause mild vasodilation and hypotension. - **Histamine (H1) Antagonism**: Weak blockade of H1 receptors contributes to its sedative properties.
動物種別の用量
- Adjunctive treatment of anxiety-related disorders (Daily medication only) · 1.9 mg/kg/day-16.2 mg/kg/day (mean = 7.3 mg/kg/day) · PO · daily · Begin at half target dose for 3 days to build tolerance.
- Adjunctive treatment of anxiety-related disorders (As needed only) · 2.2 mg/kg/day- 14 mg/kg/day (mean 7.7 mg/kg/day) · PO · PRN
- Adjunctive treatment of anxiety-related disorders (Daily medication and as needed) · 1.7 mg/kg/day-19.5 mg/kg/day (mean 7.25 mg/kg/day) · PO · daily and PRN
- Adjunctive treatment of anxiety-related disorders · 1 mg/kg PO q12h for 7 days, then up to 3 mg/kg PO q12h. · PO · q12h · 7 days initially
- Adjunctive treatment of anxiety-related disorders · 1-4.8 mg/kg PO twice daily; (titrate to effect in 1 mg increments every 7 days). · PO · q12h
- Adjunctive treatment of anxiety-related disorders (Situational) · typical starting dose between 2-5 mg/kg and adjusting upwards as necessary to get control (maximum dose 14 mg/kg/day). · PO · PRN · Given about an hour prior to the onset of anxiety.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Hypersensitivity to trazodone
- Concurrent use of MAO inhibitors (e.g., amitraz, selegiline)
- Glaucoma
- History of seizures
- Urinary retention
- Severe liver disease
有害事象
- Sedation
- Lethargy
- Ataxia
- Cardiac conduction disturbances
- Increased anxiety (paradoxical)
- Aggression (paradoxical)
- Vomiting/gagging
- Increased excitement
- Increased appetite
- Colitis
- Serotonin syndrome (rare, usually with concurrent serotonergic drugs)
- Vomiting
- Excitability
- Dry mouth
- Third eyelid protrusion (in cats)
薬物相互作用
- Antihypertensive drugs · May increase reductions in blood pressure and cause hypotension
- Aspirin · Increase risk for GI bleeding; monitor
- Azole antifungals (e.g., ketoconazole, fluconazole) · May increase trazodone blood levels
- CNS depressants · Use with trazodone may cause additive CNS depressant effects
- Digoxin · Trazodone may increase digoxin levels
- Macrolide antibiotics (e.g., erythromycin, clarithromycin) · May increase trazodone blood levels
- Metoclopramide · Increased risk for serotonin syndrome
- NSAIDs · Increased risk for GI bleeding; monitor
- Phenothiazines · May increase trazodone blood levels; cause additive CNS effects
- SSRI antidepressants (e.g., fluoxetine) · Increased risk for serotonin syndrome. Commonly used together, but monitor closely.
- Monoamine oxidase inhibitors (MAOIs) · Contraindicated; high risk of serotonin syndrome · major
- Chlorphenamine · Metabolized by CYP450 2D6; potential for altered metabolism and toxicity · moderate
- Cimetidine · Metabolized by CYP450 2D6; potential for altered metabolism and toxicity · moderate
モニタリング
- Clinical efficacy (behavioral calming)
- Adverse effects (sedation, GI upset, paradoxical excitement)
- Signs of serotonin syndrome (vomiting, diarrhea, seizures, hyperthermia, hyperesthesia, mydriasis)
- Renal function (in patients with pre-existing renal disease)
- Signs of serotonin syndrome (tremors, agitation, hyperthermia)
- Efficacy of anxiety reduction
過量投与
No specific information is available regarding trazodone overdoses in veterinary patients. In humans, the incidence of serious toxicity from trazodone overdose alone is low compared with tricyclic antidepressant overdoses. In the event of a substantial overdose, contact an animal poison control center for guidance. Monitor for profound sedation, ataxia, hypotension, and signs of serotonin syndrome.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。