硫酸阿托品
硫酸阿托品是一種天然存在的顛茄生物鹼，也是獸醫學中廣泛使用的**抗毒蕈鹼（抗膽鹼）**原型藥物。 主要臨床應用包括： - **急診醫學與心肺腦復甦術 (CPCR)**：治療具有血流動力學意義的竇性心搏過緩、竇房結停搏及不完全性房室傳導阻滯。 - **麻醉**：作為麻醉前給藥，以預防或減少呼吸道和唾液分泌，並減輕迷走神經介導的心搏過緩。 - **毒物學**：作為膽鹼能藥物過量（包括有機磷、氨基甲酸酯、毒蕈鹼類蘑菇及藍綠藻中毒）的救命解毒劑。 - **呼吸系統**：支氣管收縮疾病的輔助治療。 > **臨床要點**：雖然阿托品非常有效，但在常規麻醉前給藥方案中，其使用正逐漸減少，轉向針對性使用或替代藥物（如格隆溴銨 Glycopyrrolate），因為後者較不易穿過血腦屏障且作用時間更長。
作用機制: **Atropine** acts as a competitive, reversible antagonist at **muscarinic acetylcholine receptors (mAChRs)** (M1-M5 subtypes) located at postganglionic parasympathetic neuroeffector sites. By blocking **acetylcholine (ACh)** binding, it inhibits parasympathetic tone: - **Cardiovascular**: Blocks vagal tone at the SA and AV nodes → increases heart rate (positive chronotropy) and improves AV conduction (positive dromotropy). - **Secretions**: Inhibits glandular M3 receptors → decreases salivary, bronchial, and gastric secretions. - **Smooth Muscle**: Relaxes smooth muscle in the GI, urinary, and biliary tracts → decreases motility and spasm. - **Ocular**: Blocks M3 receptors in the pupillary sphincter and ciliary muscle → causes pupillary dilation (mydriasis) and paralysis of accommodation (cycloplegia). > **Mechanistic Note**: At very low doses, atropine can cause a paradoxical, transient bradycardia due to the blockade of presynaptic **M1 autoreceptors** on vagal postganglionic fibers, which normally inhibit ACh release. High doses may also block nicotinic receptors at autonomic ganglia and the neuromuscular junction.
各物種劑量
- Treating organophosphate toxicity · Use the dose for cattle · IV, SC, IM · as needed
- Treating organophosphate toxicity · Use the dose for cattle · IV, SC, IM · as needed
- As a preanesthetic adjuvant (geriatric patients) · 0.01-0.02 mg/kg · IM, IV · once · Do not use anticholinergics indiscriminately in geriatric patients.
- As a preanesthetic adjuvant · 0.074 mg/kg · IV, IM or SC · once
- As a preanesthetic adjuvant · 0.02-0.04 mg/kg · SC, IM or IV · once
- During cardiopulmonary cerebral resuscitation (CPCR) efforts · 0.04 mg/kg (IV or IO); 0.08-0.1 mg/kg (IT) · IV, IO, IT · every 3-5 minutes · maximum of 3 doses · For IT administration: dilute in 5-10 mL of sterile water before administering.
- Treatment of bradycardias · 0.02-0.04 mg/kg · SC, IM or IV · q4-6h
- Treatment of cholinergic toxicity · 0.2-2 mg/kg · IV, SC, IM · as needed · give 1/4th of the dose IV and the remainder SC or IM
- As a premed · 0.05 mg/kg · SC or IM · once
給藥途徑
禁忌症
- Narrow-angle glaucoma
- Synechiae (adhesions) between the iris and lens
- Hypersensitivity to anticholinergic drugs
- Tachycardias secondary to thyrotoxicosis or cardiac insufficiency
- Myocardial ischemia
- Unstable cardiac status during acute hemorrhage
- GI obstructive disease or paralytic ileus
- Severe ulcerative colitis
- Obstructive uropathy
- Myasthenia gravis (unless used to reverse adverse muscarinic effects secondary to therapy)
不良反應
- Dry mouth (xerostomia)
- Dysphagia
- Constipation
- Vomiting
- Thirst
- Urinary retention or hesitancy
- CNS stimulation, drowsiness, ataxia, seizures, respiratory depression
- Blurred vision, pupil dilation (mydriasis), cycloplegia, photophobia
- Sinus tachycardia (at higher doses)
- Paradoxical bradycardia (initially or at very low doses)
- Hypertension or hypotension
- Arrhythmias (ectopic complexes)
- Decreased gut motility (can induce colic in horses or rumen stasis in cattle)
藥物相互作用
- Amantadine · May enhance the activity or toxicity of atropine
- Anticholinergic agents (other) · May enhance the activity or toxicity of atropine
- Antihistamines (e.g., diphenhydramine) · May enhance the activity or toxicity of atropine
- Disopyramide · May enhance the activity or toxicity of atropine
- Meperidine · May enhance the activity or toxicity of atropine
- Phenothiazines · May enhance the activity or toxicity of atropine; do not use in atropine overdose
- Procainamide · May enhance the activity or toxicity of atropine
- Primidone · May enhance the activity or toxicity of atropine
- Tricyclic antidepressants (e.g., amitriptyline, clomipramine) · May enhance the activity or toxicity of atropine
- Alpha-2 agonists (e.g., dexmedetomidine, medetomidine) · Use with alpha-2 blockers may significantly increase arterial blood pressure, heart rates, and the incidence of arrhythmias. Concurrent use is controversial.
- Amitraz · Atropine may aggravate signs of amitraz toxicity, leading to hypertension and further inhibition of peristalsis
- Antacids · May decrease PO atropine absorption; give oral atropine at least 1 hour prior to oral antacids
監測
- Heart rate and rhythm
- Thirst and appetite
- Urination and defecation capability
- Mouth and secretions dryness
- Pupillary dilation (mydriasis)
過量
**Signs of Toxicity:** Extensions of pharmacologic effects: severe dry mouth, dysphagia, extreme thirst, vomiting, urinary retention, CNS signs (extreme agitation, seizures, ataxia, respiratory depression), severe tachycardia, arrhythmias, and circulatory failure. **Treatment:** - **Decontamination**: If recent oral ingestion, empty gut contents and administer activated charcoal and saline cathartics. - **Supportive Care**: Treat clinical signs supportively and symptomatically. Fluid therapy and standard treatments for shock may be instituted. - **Contraindications**: Do NOT use phenothiazines as they may contribute to anticholinergic effects. - **Antidote (Physostigmine)**: Controversial. Reserve for extreme agitation/risk of injury or severe/life-threatening supraventricular and sinus tachycardias. - *Human dose*: 2 mg IV slowly. - *Pediatric/Small Animal dose*: 0.02 mg/kg slow IV (repeat q10 minutes until reversal). - *Note*: Physostigmine adverse effects (bronchoconstriction, bradycardia, seizures) may be treated with small doses of IV atropine.
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