ヨヒンビン
ヨヒンビンはインドールアルキルアミンアルカロイドであり、特異的なα2-アドレナリン受容体拮抗薬です。獣医学では主に、α2作動薬（特にキシラジン）の鎮静および心血管作用を拮抗するために使用されます。また、アミトラズ中毒の有効な解毒剤でもあり、予防的にも使用されます。現代の臨床ではデクスメデトミジンの拮抗にはアチパメゾールが主流ですが、ヨヒンビンは依然として重要な救急および拮抗薬です。
作用機序: Yohimbine competitively blocks central and peripheral **presynaptic alpha-2 adrenergic receptors**. - **Mechanism:** By blocking these autoreceptors, yohimbine prevents the negative feedback loop that normally inhibits neurotransmitter release → **increases synaptic norepinephrine** release → enhances sympathetic outflow. - **Systemic Effects:** This surge in sympathetic tone results in increased heart rate, elevated blood pressure, CNS stimulation, and antidiuresis, effectively counteracting the profound sedation, bradycardia, and hypotension induced by alpha-2 agonists.
動物種別の用量
- Xylazine reversal (Llamas/Camelids) · 0.25 mg/kg IV or IM · IV/IM · once · Dosing specifically reported for Llamas.
- Xylazine reversal · 0.125 mg/kg IV · IV · once
- Xylazine reversal (Routine/Emergency) · IM administration preferred for routine; 0.1 mg/kg IV for emergency · IM/IV · once · IM preferred to decrease CNS/CV risks. Wait 30-45 min post-IM or 15-30 min post-IV xylazine to allow ketamine/Telazol to resolve before reversing.
- Xylazine reversal · 0.075 mg/kg IV · IV · once · ARCI UCGFS Class 2 Drug.
- Alpha2-adrenergic agonist reversal (e.g., xylazine) · 0.1 mg/kg IV · IV · once
- Xylazine reversal (Rabbits) · 0.2 mg/kg IV · IV · as needed · Also partially antagonizes ketamine and acepromazine.
- Xylazine reversal (Mice/Rats) · 0.2 mg/kg IP · IP · as needed · Also partially antagonizes ketamine and acepromazine.
- Xylazine reversal · 0.11 mg/kg IV slowly OR 0.1 mg/kg IV · IV · once
- Medetomidine reversal · 0.11 mg/kg IV · IV · once
- Amitraz toxicity reversal (centrally mediated bradycardia/hypotension) · 0.1 mg/kg IV · IV · repeat as necessary
- Amitraz toxicity (demodicosis treatment) · 0.11 mg/kg IV or 0.25 mg/kg IM (with atipamezole 50 mcg/kg IM) · IV/IM · once · Used to treat or prevent acute toxicity episodes.
- Prevention of side effects from amitraz dips · 0.1 mg/kg IV · IV · once · May give prior to, or after bathing.
- Antiemetic · 0.25-0.5 mg/kg SC or IM · SC/IM · q12h
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 yohimbine
- Renal disease (extrapolated from human medicine)
- Patients with active seizure disorders
有害事象
- Transient apprehension or anxiety
- CNS excitement
- Muscle tremors
- Hypersalivation
- Increased respiratory rate (panting)
- Hyperemic (red) mucous membranes
- Tachycardia
薬物相互作用
- Tricyclic Antidepressants · May cause severe hypertension; concurrent use is not recommended.
- Other Alpha-2 Antagonists · Additive antagonistic effects; use with caution.
- CNS Stimulants · Additive CNS stimulation and increased risk of seizures or severe agitation.
モニタリング
- CNS status (arousal level, signs of excitement or apprehension)
- Cardiac rate and rhythm
- Blood pressure (if indicated and practical)
- Respiratory rate and effort
過量投与
Overdoses can cause significant CNS and cardiovascular overstimulation. - **Experimental Data:** Dogs receiving 0.55 mg/kg (5 times the recommended dose) exhibited clinical signs of transient seizures and muscle tremors. - **Clinical Reports (APCC):** Reported findings in dogs include diarrhea, disorientation, hyperactivity, panting, tachycardia, and hypersalivation. - **Treatment:** Primarily supportive and symptomatic. Avoid further CNS stimulation and manage seizures if they occur.
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。