戊巴比妥鈉
戊巴比妥鈉是一種短效**巴比妥類藥物**,在獸醫學中歷史上被用作全身麻醉劑和鎮靜劑。由於更安全的吸入性麻醉劑和如丙泊酚(Propofol)等注射劑的出現,其治療用途現在主要限於控制**難治性癲癇重積狀態**(例如繼發於番木鱉鹼或破傷風毒素中毒)以及作為**安樂死溶液**的主要成分。 * **中樞神經系統抑制:** 能夠引起所有程度的中樞神經系統改變,從輕度鎮靜到深度昏迷和死亡。 * **心血管與呼吸系統影響:** 引起劑量依賴性的呼吸抑制和心血管改變(心搏過速、心肌收縮力下降和低血壓)。 > **臨床要點:** 戊巴比妥的治療指數狹窄,且**不具備內在鎮痛作用**。它屬於 DEA 附表 II 管制藥物(當未配製為安樂死組合產品時)。
作用機制: Pentobarbital acts as a profound **CNS depressant** through multiple mechanisms: * **GABA-A Receptor Modulation:** Binds to the barbiturate site on the GABA-A receptor, **prolonging the duration** of chloride channel opening → hyperpolarization of the postsynaptic membrane → profound CNS inhibition. At high doses, it is directly GABA-mimetic. * **Glutamate Inhibition:** Inhibits excitatory neurotransmission by blocking glutamate release and AMPA/kainate receptors. * **Neurotransmitter Release:** Inhibits the release of acetylcholine and norepinephrine. * **Calcium Channels:** At high anesthetic doses, it inhibits calcium uptake at nerve terminals.
給藥途徑
禁忌症
- Known hypersensitivity to barbiturates
- Severe liver disease
- Nephritis
- Severe respiratory depression
- Lidocaine-induced seizures
- Pregnancy (Category D - embryotoxic/teratogenic)
不良反應
- Respiratory depression (can be severe)
- Hypothermia
- Paradoxical excitement during recovery (especially in dogs)
- Cardiovascular depression (decreased contractility, hypotension)
- Severe tissue irritation and necrosis (if given perivascularly or SC)
藥物相互作用
- Acetaminophen · Increased risk for hepatotoxicity, particularly with large or chronic barbiturate doses.
- Lidocaine · Fatalities reported when treating lidocaine-induced seizures with pentobarbital; use diazepam instead.
- Phenytoin · Barbiturates may affect phenytoin metabolism and vice versa; blood level monitoring indicated.
- Rifampin · May induce enzymes that increase the metabolism of barbiturates.
- Antihistamines · May increase the CNS depressant effect of pentobarbital.
- Chloramphenicol · May increase the CNS depressant effect of pentobarbital.
- Opiates · May increase the CNS depressant effect of pentobarbital.
- Phenothiazines · May increase the CNS depressant effect of pentobarbital.
監測
- Respiratory rate, depth, and effort (ventilatory support must be available)
- Heart rate and rhythm
- Blood pressure
- Body temperature (monitor for hypothermia)
- Depth of anesthesia/sedation
過量
In dogs, the reported oral LD50 is 85 mg/kg and IV LD50 is 40-60 mg/kg. **Fatalities from ingestion of meat from animals euthanized by pentobarbital have been reported in dogs.** **Treatment:** * Removal of ingested product from the gut if appropriate (e.g., gastric lavage, activated charcoal). * Provide aggressive respiratory (ventilatory) and cardiovascular support. * Forced alkaline diuresis is of little benefit. * Peritoneal dialysis or hemodialysis may be beneficial in severe intoxications.
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。