巴比妥類藥物
巴比妥類藥物是一類作為**中樞神經系統（CNS）抑制劑**的藥物。它們能引起各種程度的中樞神經情緒改變，從矛盾性興奮到深度昏迷甚至死亡。 主要全身性影響包括： * **呼吸系統**：劑量依賴性呼吸抑制。在鎮靜劑量下，抑制程度類似正常睡眠；隨著劑量增加，延髓呼吸中樞會受到進行性抑制。 * **心血管系統**：可能引起心搏過速、心肌收縮力下降、心搏出量減少及平均動脈壓下降。 * **胃腸道**：通常會降低腸道肌肉的張力與蠕動。硫巴比妥類藥物在初期抑制後，可能會引起短暫的張力/蠕動增加。 * **肌肉骨骼**：降低運動終板對乙醯膽鹼的敏感性，提供輕度的骨骼肌鬆弛作用。 * **肝臟**：長期給藥（尤其是苯巴比妥）會導致明顯的**肝臟微粒體酵素誘導**。 > **臨床要點**：巴比妥類藥物**不具備真正的內在鎮痛活性**。在獸醫學中，它們主要用於癲癇控制（如苯巴比妥）、麻醉誘導（如硫噴妥、美索比妥）以及人道安樂死（如戊巴比妥）。
作用機制: The exact mechanisms for the CNS effects caused by barbiturates are complex and multifactorial: * **Neurotransmitter Inhibition**: They inhibit the release of excitatory neurotransmitters including **acetylcholine**, **norepinephrine**, and **glutamate**. * **GABA Modulation**: Barbiturates enhance inhibitory neurotransmission by acting on **GABA** receptors. Pentobarbital is specifically noted to be **GABA-mimetic**, directly activating GABA receptors at higher doses. * **Calcium Channel Blockade**: At high anesthetic doses, barbiturates inhibit the uptake of calcium at nerve endings, further dampening synaptic transmission.
給藥途徑
禁忌症
- Use with extreme caution in cats due to high sensitivity to respiratory depressant effects
不良反應
- Dose-dependent respiratory depression
- Cardiovascular depression (hypotension, decreased contractility)
- Paradoxical excitement
- Hypothermia (at anesthetic doses)
- Decreased gastrointestinal motility
監測
- Respiratory rate, depth, and volume
- Heart rate and blood pressure
- Body temperature (monitor for hypothermia)
- Liver enzymes (with chronic administration)
過量
Overdose can lead to profound **CNS depression**, **coma**, and **death**. * **Respiratory arrest** typically precedes cardiac arrest (occurring at doses approximately four times lower than those causing cardiac arrest). * Severe **renal impairment** may occur secondary to profound hypotensive effects during an overdose.
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