氯丙嗪
氯丙嗪是典型的吩噻嗪類衍生物，在獸醫學中歷史上被用作神經阻滯劑和鎮靜劑，但由於乙醯丙嗪（Acepromazine）效力更高且作用時間較短，現已大多被其取代。 目前主要用於小動物的**止吐**，特別是控制貓的暈車症狀。 **主要臨床重點：** * 能有效抑制狗（但對貓無效）由阿朴嗎啡引起的嘔吐，以及嗎啡引起的嘔吐。 * 無法抑制由硫酸銅或毛地黃苷引起的嘔吐。 * **幾乎沒有鎮痛作用**；對於疼痛情況必須提供適當的鎮痛藥。 * 由於會引起矛盾的興奮和共濟失調，通常禁忌用於馬匹。 * 可能引起顯著的血管擴張和低血壓；給藥前病患必須有充足的水分。
作用機制: Chlorpromazine acts primarily as a **dopamine (D2) receptor antagonist** in the central nervous system. * **Antiemetic effect:** Blocks D2 receptors in the Chemoreceptor Trigger Zone (CRTZ) of the medulla → inhibits emetic signaling to the vomiting center. * **Sedative effect:** Antagonizes central **histamine (H1)**, **alpha-1 adrenergic**, and **dopamine** receptors → depresses the reticular activating system. * **Cardiovascular effect:** Peripheral **alpha-1 adrenergic blockade** → vasodilation and potential hypotension. * Also possesses weak anticholinergic (muscarinic M1 blockade) and antiserotonergic properties.
各物種劑量
- General use · 0.55-4.4 mg/kg IV, 2.2-6.6 mg/kg IM · IV/IM · Once
- General use · 0.55-4.4 mg/kg IV, 2.2-6.6 mg/kg IM · IV/IM · Once
- General use · 2-3.5 mg/kg IV q5-6h · IV · q5-6h
- As an antiemetic · 0.5 mg/kg IV, IM or SC three to four times daily · IV/IM/SC · q6-8h
- As an antiemetic · 2 mg (total dose) per cat PO q12h · PO · q12h
- As a preanesthetic · up to 1.1 mg/kg IM 1-1.5 hours prior to surgery · IM · Once
- Premedication for cattle undergoing standing procedures · Up to 1 mg/kg IM · IM · Once · May cause regurgitation if animal undergoes general anesthesia
- Premedication · 1 mg/kg IM · IM · Once
- Premedication · 0.55-3.3 mg/kg IV; 2-4 mg/kg IM · IV/IM · Once
- Restraint · 1.1 mg/kg IM · IM · Once · Effects are at peak in 45-60 minutes
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Horses (generally not recommended due to severe ataxia and panic reactions)
- Rabbits (IM injection causes severe muscle discomfort and swelling)
- Hypovolemia or shock
- Tetanus or strychnine intoxication (due to extrapyramidal effects)
不良反應
- Hypotension
- CNS stimulation (paradoxical)
- Bradycardia or tachycardia
- Extrapyramidal signs in cats (tremors, shivering, rigidity, loss of righting reflexes)
- Lethargy
- Diarrhea
- Loss of anal sphincter tone
- Ataxia, excitation, and panic reactions in horses
- Hypothermia or hyperthermia
藥物相互作用
- Acetaminophen · Possible increased risk for hypothermia
- Antacids · May cause reduced GI absorption of oral phenothiazines
- Antidiarrheal mixtures (e.g., kaolin/pectin, bismuth subsalicylate) · May cause reduced GI absorption of oral phenothiazines
- CNS Depressant Agents (barbiturates, narcotics, anesthetics) · May cause additive CNS depression
- Dipyrone · May cause serious hypothermia
- Epinephrine · Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal)
- Opiates · May enhance hypotensive effects; chlorpromazine dosages may need reduction
- Organophosphate Agents · Effects may be potentiated; do not give phenothiazines within one month of worming with these agents
- Paraquat · Toxicity may be increased by chlorpromazine
- Phenytoin · Metabolism may be decreased if given concurrently
- Physostigmine · Toxicity may be enhanced by chlorpromazine
- Procaine · Activity may be enhanced by phenothiazines
- Propranolol · Increased blood levels of both drugs may result
監測
- Cardiac rate, rhythm, and blood pressure (if indicated and possible)
- Degree of tranquilization and anti-emetic activity
- Body temperature (especially in extreme ambient temperatures)
過量
Small overdoses typically cause somnolence. Larger overdoses can cause serious effects including **coma, agitation/seizures, ECG changes/arrhythmias, hypotension, and extrapyramidal effects**. * **Treatment:** Most overdoses are managed with supportive care and monitoring. Massive oral overdoses should be treated by emptying the gut if possible. * **Hypotension Management:** Do NOT treat hypotension with epinephrine (due to epinephrine reversal). Use **phenylephrine** or **norepinephrine** (levarterenol). * **Seizure Management:** Control seizures with barbiturates or diazepam.
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