ハロタン

解説

ハロタン,ハロセンともいう。吸入麻酔薬の一つ。1958年イギリスのICI社が合成したもので，クロロホルム類似の麻酔作用を示し，麻酔力はエーテルの4倍，クロロホルムの2倍と評価されている。エーテルと異なり不燃性で，吸入に際し，気道粘膜を刺激せず，通常あらゆる種類の手術に全身麻酔の目的で用いられる。鎮痛効果はクロロホルムに劣り，麻酔の導入には1.5～2.0v/v％以上の濃度が必要とされる。手術に必要な筋弛緩作用は弱いので，必要に応じ筋弛緩薬を併用するが，著しい筋弛緩を要しない手術には好んで用いられる。不燃焼性の揮発性液体。甘みがあり，不快な臭気はない。沸点 50.2℃。光に弱く，0.01%のチモールとともに保存。水に少し溶け，石油エーテルその他の油脂溶剤とは混る。ヒトや家畜の吸入麻酔薬として使われる。

用途

吸入麻酔剤、麻酔作用はエーテルの4倍、クロロホルムの2倍

効能

吸入麻酔薬

化学的特性

Halothane is a highly volatile, nonflammable, colorless liquid. Sweet odor.

使用

Halothane is used as a clinical anesthetic.

定義

ChEBI: A haloalkane comprising ethane having three flouro substituents at the 1-position as well as bromo- and chloro substituents at the 2-position.

生物学の機能

Halothane (Fluothane) depresses respiratory function, leading to decreased tidal volume and an increased rate of ventilation. Since the increased rate does not adequately compensate for the decrease in tidal volume, minute ventilation will be reduced; plasma PaCO₂ rises, and hypoxic drive is depressed.With surgical anesthesia, spontaneous ventilation is inadequate, and the patient’s ventilation must be controlled.
Halothane administration can result in a marked reduction in arterial blood pressure that is due primarily to direct myocardial depression, which reduces cardiac output. The fall in pressure is not opposed by reflex sympathetic activation, however, since halothane also blunts baroreceptor and carotid reflexes. Systemic vascular resistance is unchanged, although blood flow to various tissues is redistributed. Halothane also sensitizes the heart to the arrhythmogenic effect of catecholamines. Thus, maintenance of the patient’s blood pressure with epinephrine must be done cautiously.

一般的な説明

Halothane is a nonflammable, nonpungent, volatile, liquid,halogenated (F, Cl, and Br) ethane (bp＝50°C), introducedin 1956. Halothane may increase heart rate, cause cardiacarrhythmias, increase cerebral blood flow, and increase intracranialpressure.It can undergo spontaneous oxidationwhen exposed to ultraviolet light to yield HCl, HBr, Cl ,Br^- , and phosgene (COCl₂). To prevent oxidation it ispackaged in amber bottles with a low concentration of thymol(0.01%) as a stabilizer. The drug has a high potency(MAC＝0.75%), a blood:gas partition coefficient of 2.4,and high adipose solubility. Halothane undergoes both reductiveand oxidative processes with up to 20% of the doseundergoing metabolism .The trifluoroacetylchloride metabolite is electrophilic and can form covalentbonds with proteins leading to immune responses andhalothane hepatitis upon subsequent halothane exposure.Halothane hepatitis is rare with 1 case reported for every6,000 to 35,000 patients exposed.

空気と水の反応

Slightly water soluble.

反応プロフィール

2-BROMO-2-CHLORO-1,1,1-TRIFLUOROETHANE is sensitive to exposure to light. Incompatible with oxidizing materials. Tarnishes or corrodes most metals, with the exception of chromium, nickel and titanium. When moisture is present, 2-BROMO-2-CHLORO-1,1,1-TRIFLUOROETHANE attacks aluminum, brass and lead, but not copper. Contact causes rubber and some plastics to deteriorate rapidly.

健康ハザード

Health hazard may arise from exposure tohigh concentrations of vapors. The target sites are the central nervous system, car diovascular system, and liver. The toxiceffects include depression of the central ner vous system, nausea, vomiting, increasedbody temperature, excitability, arrhythmias,vasodilatation, hepatitis, and liver necrosis.An anesthetic effect in humans is noted atan exposure level of 10,000 ppm. Repeatedexposure to halothane at anesthetic concen trations may result in hepatic lesions andnecrosis. Contact of liquid with the eyes mayresult in severe irritation. The lethal con centration in humans for a 3-hour exposureperiod is in the range of 7000 ppm.
LC50 value, inhalation (mice): 22,000 ppm/10 min
LD50 value, oral (guinea pigs): 6000 mg/kg
No mutagenic effect was observed. Carcino genicity in animals has not been reported.

火災危険

Literature sources indicate that 2-BROMO-2-CHLORO-1,1,1-TRIFLUOROETHANE is nonflammable.

臨床応用

The use of inhaled anesthetics and halothane in particularcan produce malignant hyperthermia (MH) in geneticallysusceptible individuals. This results in an increase inbody temperature, tachycardia, tachypnea, acidosis, andrhabdomylolysis. MH is a result of the excessive release ofcalcium from the sarcoplasmic reticulum (SR). Patientswith an inherited mutation in the ryanodine receptor(RYR1), which is located in the SR, are at an increased riskof developing MH when exposed to an inhaled anesthetictriggering agent. Treatment entails discontinuing the anestheticagent, rapid cooling, intravenous dantrolene sodium,and supportive measures. MH has been reported to occurwith all anesthetics agents and with succinylcholine, a depolarizingneuromuscular blocker. The combination ofhalothane and succinylcholine appears to trigger a great extentof the MH episodes. Patients with a family history ofMH can be genetically screened for MH susceptibility viathe caffeine–halothane contracture test. This test is invasiverequiring a piece of skeletal muscle to conduct and it isexpensive costing approximately $5,000 (cost in 2008).Noninvasive molecular genetic screening is currently beingdeveloped.

職業ばく露

Halothane is used as an inhalation anesthetic. It has been estimated that halothane accounts for two-thirds of all anesthetics.

輸送方法

UN3082 Environmentally hazardous substances, liquid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous haz ardous material, Technical Name Required.

不和合性

May attack rubber and some plastics; sensitive to light. Light causes decomposition. May be stabilized with 0.01% thymol. Halothane is incompatible with oxidizers (chlorates, nitrates, peroxides, permanga nates, perchlorates, chlorine, bromine, fluorine, etc.); con tact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Tarnishes or corrodes most metals, with the exception of copper, chromium, nickel, and titanium. Attacks aluminum, brass and lead in the presence of moisture. Attacks rubber and causes some plastics to deteriorate rapidly.

廃棄物の処理

The compound is mixed with a combustiblesolvent and burned in a chemical incineratorequipped with an afterburner and scrubber.