阿替美唑
阿替美唑是一種高選擇性且強效的 **α2-腎上腺素受體拮抗劑**，在獸醫學中主要用作美托咪定 (medetomidine) 和右美托咪定 (dexmedetomidine) 等 α2-激動劑的逆轉劑。它也可用於標示外用途，以逆轉其他 α2-激動劑（如甲苯噻嗪 xylazine、雙甲脒 amitraz 和可樂定 clonidine）。 **臨床要點：** * 阿替美唑的 α2:α1 選擇性比例為 8526:1，比育亨賓 (yohimbine) 或妥拉蘇林 (tolazoline) 等較舊的逆轉劑更具特異性。這種高特異性使其能快速、乾淨地逆轉鎮靜，且心血管副作用較少。 * 由於它會迅速逆轉鎮靜**和鎮痛**作用，因此在給藥前必須評估病患的疼痛情況；如果病患接受了會引起疼痛的處置，應提供替代的鎮痛藥物（如鴉片類藥物、非類固醇消炎藥）。 * 阿替美唑的半衰期相對較短（在狗體內約 2-3 小時）。在治療長效 α2-激動劑（如雙甲脒）中毒時，毒性物質的作用時間可能超過逆轉劑，導致再次鎮靜，此時可能需要重複給藥。
作用機制: 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.
各物種劑量
- 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
給藥途徑
禁忌症
- Reptiles (Intravenous administration is contraindicated due to profound hypotension)
不良反應
- Vomiting
- Diarrhea
- Hypersalivation
- Tremors
- Brief excitation or apprehensiveness
- Aggression upon rapid waking
- Profound hypotension (if given IV in reptiles)
- Loss of analgesia
藥物相互作用
- 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
監測
- Level of sedation and analgesia
- Heart rate
- Body temperature
過量
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.
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