沙丁胺醇 (Albuterol / Salbutamol)
沙丁胺醇（國際通用名為 **salbutamol**）是一種短效 $\beta_2$-腎上腺素受體激動劑 (SABA)。在獸醫學中被廣泛用作強效的**支氣管擴張劑**，以緩解與下呼吸道疾病相關的支氣管痙攣和咳嗽。 主要臨床應用包括： * **貓氣喘 (Feline Asthma)**：主要作為急性氣喘發作時的「急救」吸入劑。 * **犬慢性支氣管炎**：提供支氣管痙攣的症狀緩解。 * **馬復發性呼吸道阻塞 (RAO / 氣喘)**：用於急性緩解呼吸窘迫。 > **臨床要點**：雖然對於急性急救治療非常有效，但不建議長期單獨使用消旋沙丁胺醇（特別是在貓）。消旋混合物中的 S-對映異構體隨著時間推移可能會引起反常的呼吸道發炎。長期管理應理想地搭配吸入性皮質類固醇（例如 fluticasone）使用。
作用機制: Albuterol selectively binds to and stimulates **$\beta_2$-adrenergic receptors** on bronchial smooth muscle. **Mechanism Pathway**: $\beta_2$-receptor activation $\rightarrow$ stimulates **adenylyl cyclase** $\rightarrow$ increases intracellular **cyclic AMP (cAMP)** $\rightarrow$ activates **protein kinase A (PKA)** $\rightarrow$ decreases intracellular calcium concentrations $\rightarrow$ results in **smooth muscle relaxation** and bronchodilation. * **Secondary Effects**: It also stabilizes mast cell membranes (preventing inflammatory mediator release) and increases mucociliary clearance. * **Metabolic/Electrolyte Effects**: Beta-adrenergic stimulation activates the **$Na^+/K^+$-ATPase pump**, driving potassium from the serum into the intracellular space, which can cause temporary hypokalemia. * **Cardiac Effects**: At standard doses, it has minimal $\beta_1$ (cardiac) activity, but at high doses or in sensitive individuals, it can cause tachycardia.
各物種劑量
- Feline asthma (mild symptoms) · one puff albuterol as needed with one puff of 110 micrograms fluticasone twice daily. · Inhalation · PRN · Using the 90 micrograms/puff aerosol albuterol inhaler and an appropriate spacer and mask.
- Feline asthma (moderate symptoms) · albuterol one puff as needed with a 5 day course of prednisone at 1 mg/kg PO daily, and 220 micrograms of fluticasone twice daily. · Inhalation · PRN
- Feline asthma (severely affected/emergency) · 90 micrograms (one puff) albuterol every 30 minutes as needed. · Inhalation · q30min PRN · Should be treated on an emergency basis with oxygen and an intravenous dose of a glucocorticoid.
- Feline asthma (chronic therapy) · 90 micrograms albuterol as needed · Inhalation · PRN · Should include fluticasone 220 micrograms twice daily and 1 mg/kg prednisone every other day.
- Feline asthma (intermittent signs) · two puffs into an appropriate spacer ( e.g., Aerokat ®) twice daily; cat should breathe through the mask and spacer for 7-10 seconds. Positive clinical effect should be seen within 5-10 minutes. Can be used every 1/2 hour for 2-4 hours in crisis. · Inhalation · BID or q30min in crisis · For intermittent signs (e.g., wheeze, increased cough or respiratory rate and effort at rest).
- Rescue therapy (respiratory difficulty at rest) · 360 micrograms (4 puffs) inhaled; if severe airway obstruction, may give at 15 minute increments for up to 2 hours. Continue as needed every 4-6 hours. · Inhalation · q15min up to 2h, then q4-6h PRN · Beneficial effects may last approximately 1 hour in severely affected horses. ARCI UCGFS Class 3 Drug.
- Moderate to severe respiratory disease · 360 micrograms followed in 5 minutes with aerosolized corticosteroid (beclomethasone or fluticasone) therapy. · Inhalation
給藥途徑
禁忌症
- Known hypersensitivity to albuterol
- Use with extreme caution in patients with cardiac disease (especially concurrent arrhythmias)
- Use with caution in patients with diabetes, hyperthyroidism, hypertension, or seizure disorders
- Use during late stages of pregnancy (may inhibit uterine contractions)
- Known hypersensitivity to salbutamol
- Severe cardiac tachyarrhythmias
不良反應
- Tachycardia
- Tremors and trembling
- CNS excitement, nervousness, and agitation
- Dizziness
- Hypokalemia (decreased serum potassium)
- Paradoxical airway inflammation in cats (associated with chronic use of the S-enantiomer in racemic albuterol)
- Muscle tremors
- Restlessness or excitement
- Hypokalemia (with high doses)
藥物相互作用
- Beta-adrenergic blocking agents (e.g., propranolol) · May antagonize the bronchodilatory actions of albuterol
- Digoxin · Albuterol may increase the risk of cardiac arrhythmias · moderate
- Inhalation anesthetics (e.g., halothane, isoflurane, methoxyflurane) · May predispose the patient to ventricular arrhythmias, particularly in patients with preexisting cardiac disease
- Other sympathomimetic amines · Concurrent use may increase the risk of developing adverse cardiovascular effects
- Tricyclic antidepressants or Monoamine oxidase inhibitors (MAOIs) · May potentiate the vascular effects of albuterol
- Propranolol (and other non-selective beta-blockers) · Antagonizes the bronchodilating effects of salbutamol · major
- Loop or Thiazide Diuretics · May exacerbate hypokalemia · moderate
監測
- Clinical symptom improvement (respiratory rate, effort)
- Thoracic auscultation
- Blood gases (if indicated in severe respiratory distress)
- Cardiac rate and rhythm (especially in overdose or susceptible patients)
- Serum potassium levels (early in therapy if animal is susceptible to hypokalemia)
- Respiratory rate and effort
- Heart rate and rhythm
- Serum potassium levels (if used frequently or in high doses)
過量
Significant overdose (often occurring when **dogs puncture an aerosol canister with their teeth**) leads to massive systemic absorption and severe sympathomimetic toxicity. **Clinical Signs**: * Severe tachycardia and arrhythmias (extrasystoles) * Hypertension * Tremors, agitation, and CNS stimulation * Panting, tachypnea, and fever * Vomiting * Mydriasis * **Hypokalemia** and hypophosphatemia (due to intracellular shifts) **Treatment**: * **Oral Ingestion (Tablets)**: If recent and asymptomatic, perform standard decontamination (emesis, activated charcoal, cathartic). * **Inhaler Puncture**: Decontamination is generally *not* effective as absorption across the oral mucosa is extremely rapid. * **Medical Management**: * Use **beta-blocking agents** (e.g., atenolol, metoprolol, or propranolol) to control severe tachycardia and arrhythmias. * Administer **diazepam** for severe tremors or agitation. * Monitor electrolytes closely; **potassium supplementation** via IV fluids is frequently required to correct hypokalemia. * Contact an animal poison control center for guided management.
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