毒扁豆鹼
毒扁豆鹼是一種可逆的**膽鹼酯酶抑制劑**，在獸醫學中主要用於伊維菌素 (ivermectin) 中毒的輔助治療、作為犬馬猝睡症/猝倒症的誘發診斷試劑，以及中樞性抗膽鹼藥物中毒的解毒劑。 **臨床要點：** * 與四級胺類膽鹼酯酶抑制劑（如新斯狄明 neostigmine）不同，毒扁豆鹼是一種**三級胺**。 * 這種結構差異使其能夠輕易穿透**血腦屏障 (BBB)**，因此對治療「中樞性」抗膽鹼毒性特別有效。 * 由於能進入中樞神經系統，其引發中樞毒性副作用（如癲癇）的風險也較高。 * 由於治療指數狹窄且可能產生嚴重副作用，通常僅保留用於危及生命的中樞神經毒性治療。
作用機制: Physostigmine reversibly inhibits the enzyme **acetylcholinesterase** → prevents the hydrolysis and destruction of **acetylcholine (ACh)** → increases the concentration of ACh at both muscarinic and nicotinic receptor sites. Because it is a lipophilic tertiary amine, it crosses the blood-brain barrier and exerts its cholinergic effects both **centrally** and **peripherally**. This widespread cholinergic stimulation leads to miosis, bronchoconstriction, hypersalivation, and increased gastrointestinal motility.
各物種劑量
- For reversal of tall larkspur (Delphinium barbeya) poisoning · 0.04-0.08 mg/kg · IV · As needed · Administer rapidly; serial injections may be necessary.
- Provocative test in diagnosing cataplexy or narcolepsy · 0.05-0.1 mg/kg · IV · Once · Administer slow IV. Will precipitate a cataplectic attack within 3-10 minutes. Untoward effects may include colic or cholinergic stimulation. Note: RCI Class 3 drug.
- Provocative test in diagnosing cataplexy or narcolepsy · 0.06-0.08 mg/kg · IV · Once · Lack of positive response does not rule out diagnosis. Diarrhea can occur and caution is advised as horse can cause colic.
- To temporarily reverse the CNS effects of ivermectin toxicosis in support of the diagnosis · 1 mg (total dose) · IV · Once
- To temporarily reverse the CNS effects of ivermectin toxicosis in support of the diagnosis · 1 mg (total dose)/12 hours · IV · q12h · May reverse ivermectin-induced coma for 30-90 minutes. In comatose patients, it does not appear to induce seizures, but seizure-like activity can be observed in patients with only minor ataxia and confusion.
- Provocative test for narcolepsy/cataplexy · 0.025 mg/kg · IV · Once · Wait 9-15 minutes and observe response to stimulus. If clinical signs do not appear, may try a higher dose of 0.05 mg/kg. Subsequent testing can be done at doses of 0.075 mg/kg and 1 mg/kg. Increased severity of signs persisting for 15-45 minutes is indicative of cataplexy/narcolepsy.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Prior hypersensitivity reactions to physostigmine or sulfites
- Bronchoconstrictive disease (asthma)
- Gangrene
- Diabetes mellitus
- Cardiovascular disease
- Mechanical obstruction of the GI or urinary tract
- Any vagotonic state
- Concurrent use of choline esters or depolarizing neuromuscular blocking agents
不良反應
- Miosis
- Bronchial constriction
- Hypersalivation
- Muscle weakness
- Sweating (in species with sweat glands)
- Seizures
- Bradycardia
- Tachycardia
- Asystole
- Nausea
- Vomiting
- Diarrhea
- Depolarizing neuromuscular block
- Pulmonary edema
- Respiratory paralysis
藥物相互作用
- Choline esters (bethanechol, carbachol, methacholine) · May cause additive adverse cholinergic effects.
- Organophosphates · May cause additive adverse cholinergic effects.
- Succinylcholine · High doses of physostigmine may cause muscle fasciculations or depolarization block, which may be additive to the effects of succinylcholine-like neuromuscular blockers.
監測
- Direct patient supervision is required
- Heart rate
- Blood pressure
- ECG/Heart rhythm (especially if heart rate is abnormal)
- Signs of cholinergic crisis (salivation, lacrimation, urination, defecation, dyspnea, emesis)
過量
Overdoses or acute toxicity can be **life-threatening** and may result in a severe cholinergic crisis (seizures, bradycardia, asystole, respiratory paralysis). * **Supportive Care:** Because of the short duration of effect, supportive care (including mechanical ventilation and repeated bronchial aspiration) may be sufficient in some cases. * **Antidote (Muscarinic):** Administration of **IV atropine** is the primary treatment for cholinergic toxicity. Re-administration may be required. * **Antidote (Nicotinic):** **Pralidoxime (2-PAM)** may be useful in reversing the ganglionic and skeletal muscle effects of physostigmine. * Contact an animal poison control center for case management assistance.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。