アチパメゾール
アチパメゾールは高選択的かつ強力な**α2アドレナリン受容体拮抗薬**であり、獣医学において主にメデトミジンやデクスメデトミジンなどのα2作動薬の拮抗薬（リバーサル剤）として使用されます。また、キシラジン、アミトラズ、クロニジンなどの他のα2作動薬を拮抗するための適応外使用も行われます。 **臨床上のポイント:** * アチパメゾールのα2:α1選択性比は8526:1であり、ヨヒンビンやトラゾリンなどの古い拮抗薬よりもはるかに特異性が高いです。この高い特異性により、心血管系の副作用が少なく、迅速かつクリーンな覚醒が得られます。 * 鎮静だけでなく**鎮痛作用も**急速に拮抗するため、投与前に患者の痛みを評価する必要があります。痛みを伴う処置を受けた場合は、代替の鎮痛薬（オピオイド、NSAIDsなど）を投与すべきです。 * アチパメゾールの半減期は比較的短いです（犬で2〜3時間）。長時間作用型のα2作動薬（アミトラズなど）の中毒を治療する場合、原因物質の作用が拮抗薬よりも長く続き、再鎮静を引き起こす可能性があるため、反復投与が必要になることがあります。
作用機序: Atipamezole competitively binds to central and peripheral **$\alpha_2$-adrenergic receptors**, displacing alpha-2 agonists. By blocking these receptors, it inhibits the negative feedback loop on presynaptic neurons $\rightarrow$ increases the release of **norepinephrine** into the synaptic cleft $\rightarrow$ leads to rapid arousal, reversal of sedation, increased heart rate, increased blood pressure, and loss of analgesia. It also antagonizes the diuretic action of alpha-2 agonists like xylazine.
動物種別の用量
- For reversal of alpha2-adrenergic agonists in caprine species · 0.02-0.1 mg/kg IV to effect · IV · Once
- Small ruminants · 0.1-0.2 mg/kg slow IV or IM · IV/IM · Once · As a rule of thumb, if induction included ketamine or Telazol do not reverse alpha2 sooner than 30 and ideally 60 minutes after induction. This will allow enough of the ketamine or tiletamine to be metabolized.
- For reversal of alpha2-adrenergic agonists in ovine species · 0.02-0.1 mg/kg IV to effect · IV · Once
- Small ruminants · 0.1-0.2 mg/kg slow IV or IM · IV/IM · Once · As a rule of thumb, if induction included ketamine or Telazol do not reverse alpha2 sooner than 30 and ideally 60 minutes after induction. This will allow enough of the ketamine or tiletamine to be metabolized.
- For reversal of medetomidine · Give IM an equal volume of Antisedan® and Domitor® is administered (mL per mL). The actual concentration of Antisedan® will be 5X that of Domitor®, as Antisedan® is 5 mg/mL versus Domitor®'s 1 mg/mL. · IM · Once
- For reversal of medetomidine · As above, but may give IV as well as IM. If it has been at least 45 minutes since medetomidine was given, may give atipamezole at half the volume of medetomidine if administered IV. If after 10-15 minutes an IM dose of atipamezole has not seemed to reverse the effects of medetomidine, an additional dose of atipamezole at 1/2 the volume of the medetomidine dose may be given. · IV/IM · Once, may repeat
- For reversal of dexmedetomidine · 0.2 mg/kg IM or IV · IM/IV · Once
投与経路
禁忌
- Reptiles (Intravenous administration is contraindicated due to profound hypotension)
有害事象
- Vomiting
- Diarrhea
- Hypersalivation
- Tremors
- Brief excitation or apprehensiveness
- Aggression upon rapid waking
- Profound hypotension (if given IV in reptiles)
- Loss of analgesia
薬物相互作用
- Alpha-1 adrenergic blockers (e.g., prazosin) · Atipamezole can partially block alpha-1 receptors and reduce the effects of prazosin.
- Alpha-2 adrenergic agonists (e.g., detomidine, clonidine, brimonidine, xylazine, amitraz) · Atipamezole can reduce the effects (toxic or therapeutic) of these agents.
- Medetomidine · Reverses sedative, analgesic, and cardiovascular effects (intended therapeutic interaction) · minor
- Dexmedetomidine · Reverses sedative, analgesic, and cardiovascular effects (intended therapeutic interaction) · minor
- Ketamine · If atipamezole is given less than 30 minutes after a medetomidine/ketamine combination in cats, it can cause severe CNS excitation during recovery. · major
- Other alpha-2 antagonists · Additive antagonistic effects · moderate
- Hypotensive agents · May exacerbate transient hypotension · minor
モニタリング
- Level of sedation and analgesia
- Heart rate
- Body temperature
過量投与
Dogs receiving up to 10X the listed dosage apparently tolerated the drug without major effects. **Clinical signs of overdose:** * Panting * Excitement * Trembling * Vomiting * Soft or liquid feces * Vasodilatation of sclera * Muscle injury at the IM injection site Specific overdose therapy should generally not be necessary as effects are typically transient.
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。