Atropine
**Atropine** is a classic anticholinergic agent used primarily in veterinary medicine to treat bradycardia, dilate pupils for ophthalmic examinations, and manage specific toxicities (such as organophosphate and carbamate poisoning). It is also used in conjunction with anticholinesterase drugs during the antagonism of neuromuscular blockade. > **Clinical Warning:** Routine administration prior to anaesthesia as part of premedication is no longer recommended. It is better to monitor heart rate and administer atropine specifically to manage a low heart rate if necessary.
กลไกการออกฤทธิ์: Atropine competitively **blocks the action of acetylcholine** at **muscarinic receptors** located at the terminal ends of the parasympathetic nervous system. This blockade → reverses parasympathetic effects → produces **mydriasis** (pupil dilation), **tachycardia**, **bronchodilation**, and general inhibition of gastrointestinal function.
ขนาดยาตามชนิดสัตว์
- Ophthalmic (mydriasis) · 1 drop in the affected eye · topical · q12-24h to cause mydriasis, then once q24-96h to maintain mydriasis
- Bradyarrhythmias · 0.01-0.03 mg/kg i.v. or 0.03-0.04 mg/kg i.m. · IV/IM · PRN · Low doses may exacerbate bradycardia; repetition of the dose will usually promote an increase in heart rate. IM dose can be given to prevent development of bradycardia during administration of potent opioids such as fentanyl.
- Organophosphate poisoning · 0.2-0.5 mg/kg (¼ dose i.v., ¾ i.m., s.c.) to effect; repeat as necessary; or 0.1-0.2 mg/kg (½ i.v., ½ i.m.) then i.m. q6h · IV/IM/SC · PRN or q6h
- Neuromuscular blockade antagonism · 0.04 mg/kg i.v. · IV · PRN · with edrophonium (0.5-1.0 mg/kg)
- Ophthalmic (mydriasis) · 1 drop in the affected eye · topical · q12-24h to cause mydriasis, then once q24-96h to maintain mydriasis
- Bradyarrhythmias · 0.01-0.03 mg/kg i.v. or 0.03-0.04 mg/kg i.m. · IV/IM · PRN · Low doses may exacerbate bradycardia; repetition of the dose will usually promote an increase in heart rate. IM dose can be given to prevent development of bradycardia during administration of potent opioids such as fentanyl.
- Organophosphate poisoning · 0.2-0.5 mg/kg (¼ dose i.v., ¾ i.m., s.c.) to effect; repeat as necessary; or 0.1-0.2 mg/kg (½ i.v., ½ i.m.) then i.m. q6h · IV/IM/SC · PRN or q6h
- Neuromuscular blockade antagonism · 0.04 mg/kg i.v. · IV · PRN · with edrophonium (0.5-1.0 mg/kg)
ขนาดยาเป็นข้อมูลอ้างอิงทางคลินิกสำหรับสัตวแพทย์ผู้มีใบอนุญาต โปรดตรวจสอบกับฉลากล่าสุดและผู้ป่วยแต่ละรายเสมอ
วิธีการให้ยา
ข้อห้ามใช้
- Glaucoma
- Lens luxation
- Keratoconjunctivitis sicca (KCS / dry eye)
อาการไม่พึงประสงค์
- Sinus tachycardia
- Blurred vision (due to mydriasis)
- Drying of bronchial secretions
- Increased intraocular pressure (IOP)
- Reduced tear production
- Ventricular arrhythmias
- Hypersalivation (especially in cats, due to bitter taste of ophthalmic drops)
- Ileus (rare in small animals)
- Vomiting (rare in small animals)
อันตรกิริยาระหว่างยา
- Bromides, iodides, sodium bicarbonate, alkalis, noradrenaline · Incompatible when mixed together · major
- Antihistamines · May enhance the activity of atropine · moderate
- Pethidine · May enhance the activity of atropine · moderate
- Benzodiazepines · May enhance the activity of atropine · moderate
- Phenothiazines · May enhance the activity of atropine · moderate
- Thiazide diuretics · May enhance the activity of atropine · moderate
- Sympathomimetics · May enhance the activity of atropine · moderate
- Alpha-2 agonists · Combining is not recommended · major
- Amitraz · May aggravate toxicity signs, leading to hypertension and gut stasis · major
- Tricyclic Antidepressants · Additive anticholinergic effects · moderate
- Alpha-2 Agonists (e.g., Dexmedetomidine) · May cause paradoxical hypertension and significantly increased myocardial workload; concurrent use is generally discouraged · major
- Metoclopramide · Atropine antagonizes the prokinetic effects of metoclopramide on the GI tract · moderate
การติดตาม
- Heart rate and rhythm (ECG)
- Pupillary light reflex and pupil size
- Intraocular pressure (IOP)
- Tear production (Schirmer Tear Test)
การได้รับยาเกินขนาด
Overdose may lead to severe sinus tachycardia, ventricular arrhythmias (which may be treated with lidocaine if severe), extreme mydriasis, severe drying of secretions, and gastrointestinal stasis.
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