ドキサプラム
ドキサプラムは中枢神経系（CNS）および呼吸興奮薬です。獣医療では主に、全身麻酔中や麻酔後の呼吸刺激、および覚醒を早めるために使用されます。また、浅い麻酔下での**喉頭機能の評価**（喉頭麻痺の診断など）においても非常に有用です。深い吸気努力を誘発するため、披裂軟骨の動きを評価しやすくなります。 > **臨床上のポイント：** 歴史的には、難産や帝王切開後の新生児の呼吸を刺激するために（舌下や臍静脈経由で）日常的に投与されていました。**しかし、現在この使用法には大きな議論があります。** ドキサプラムは心筋および脳の酸素需要を著しく増加させます。すでに低酸素状態にある新生児にとって、これは有害となる可能性があります。現在の新生児蘇生ガイドラインでは、興奮薬の使用よりも、気道の確保、酸素供給、および陽圧換気（人工呼吸器によるサポート）を優先することが強く推奨されています。
作用機序: Doxapram is a generalized CNS stimulant. Its respiratory effects are primarily driven by: 1. **Direct stimulation** of the **medullary respiratory centers**. 2. **Reflex activation** of peripheral **carotid and aortic chemoreceptors**. This dual action leads to transient increases in tidal volume and respiratory rate. > **Mechanistic Note:** While doxapram increases respiratory effort, it simultaneously increases the overall work of breathing, metabolic rate, and carbon dioxide production. Consequently, it does not reliably improve arterial oxygenation, which is why it cannot replace mechanical ventilation in severely hypoxic patients.
動物種別の用量
- Gas anesthesia recovery · 1.1 mg/kg IV · IV · May repeat in 15-20 minutes if necessary · Adjust dosage for depth of anesthesia, respiratory volume and rate.
- Barbiturate anesthesia recovery · 5.5-11 mg/kg IV · IV · May repeat in 15-20 minutes if necessary · Adjust dosage for depth of anesthesia, respiratory volume and rate.
- To initiate or stimulate respirations in neonates after caesarian section or dystocia · 1-2 drops (1-2 mg) SC or sublingually · SC/SL · Once · Depending on severity of respiratory crisis.
- To stimulate respiratory function in neonates · 0.1 mL (2 mg) IV (IM or SL also possible) · IV/IM/SL · Once · Most likely to be beneficial to increase efforts in neonates with low-frequency, gasping, erratic pattern of breathing after receiving oxygen therapy.
- Primary apnea in asphyxic calves when intubation and mechanical ventilation are not feasible · 2 mg/kg IV · IV · Once · Contraindicated in premature calves or other patients with clinical signs indicative of lung immaturity.
- Primary apnea in newborn calves · 2 mg/kg IV · IV · Once
- Halothane, methoxyflurane anesthesia recovery · 0.44 mg/kg IV · IV · May repeat in 15-20 minutes if necessary · Adjust dosage for depth of anesthesia, respiratory volume and rate. ARCI UCGFS Class 2 Drug.
- Chloral hydrate ± magnesium sulfate anesthesia recovery · 0.55 mg/kg IV · IV · May repeat in 15-20 minutes if necessary · Adjust dosage for depth of anesthesia, respiratory volume and rate. ARCI UCGFS Class 2 Drug.
投与経路
禁忌
- Patients receiving mechanical ventilation
- Hypersensitivity to doxapram
- Seizure disorders
- Head trauma or cerebrovascular accidents (CVA)
- Uncompensated heart failure
- Severe hypertension
- Respiratory failure secondary to neuromuscular disorders
- Airway obstruction
- Pulmonary embolism
- Pneumothorax
- Acute asthma
- Dyspnea
- Hypoxia not associated with hypercapnia
- Premature calves or patients with clinical signs of lung immaturity
有害事象
- Hypertension
- Arrhythmias
- Tachycardia
- Seizures (at high doses)
- Hyperventilation leading to respiratory alkalosis
- Increased myocardial oxygen demand
- Reduced cerebral blood flow
- Skeletal muscle hyperactivity
薬物相互作用
- General Anesthetics (e.g., halothane, enflurane) · Doxapram may increase epinephrine release and sensitize the myocardium to catecholamines. Use should be delayed for ~10 minutes after discontinuing these anesthetics.
- Muscle Relaxants · Doxapram may mask the effects of muscle relaxant drugs.
- Sympathomimetic Agents · Additive pressor (blood pressure increasing) effects may occur.
モニタリング
- Respiratory rate and effort
- Cardiac rate and rhythm
- Blood gases (if available and indicated)
- CNS level of excitation and reflexes
- Blood pressure (if indicated)
過量投与
The reported LD50 for IV administration in neonatal dogs and cats is approximately 75 mg/kg. **Clinical signs of overdosage include:** - Respiratory alkalosis - Hypertension - Skeletal muscle hyperactivity - Tachycardia - Generalized CNS excitation, including seizures **Treatment:** Treatment is primarily supportive. Drugs such as short-acting IV barbiturates may be used to help decrease CNS hyperactivity. Oxygen therapy may be necessary.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。