ミダゾラム
Midazolam
Midazolam hydrochloride
別名: Versed · Dormicum · Dormonid · Fulsed · Hypnovel · Midaselect · Zolamid · Buccolam · Epistatus · Midazolam HCl · Ro-21-3981/003 · Midazolamum · Midazolam hydrochloride
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
監査済み v13 用量エビデンス
確認済み・計算対象外のエビデンス確認済み・計算対象外のエビデンス (1)
エビデンス表示のみ（自動計算対象外）
Preanesthetic agent (extra-label)
Preanesthetic agent (extra-label): 0.5 – 5 mg/kg IM or IV
必ず考慮する臨床コンテキスト (2)
- NOTE: There are many potential combinations that have been suggested; the following are examples and not inclusive. For additional information, refer to other anesthesia-specific references. 25
- Store midazolam injection at room temperature (15°C-30°C [59°F-86°F]) and protected from light. After being frozen for 3 days and allowed to thaw at room temperature, the injectable product is physically stable. Midazolam is stable at a pH range of 3 to 3.6.
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
ミダゾラムは、獣医療において麻酔前鎮静薬、筋弛緩薬、および抗てんかん薬として広く使用される短時間作用型の注射用ベンゾジアゼピン系薬物です。
臨床上のポイント：
- 独自の溶解性： ジアゼパムとは異なり、ミダゾラムはバイアル内（pH < 4）では水溶性ですが、生理的な体内のpH（7.4）では高い脂溶性を示します。これにより、他の水溶性薬物（オピオイドやケタミンなど）と沈殿することなく安全に混合できます。
- 筋肉内吸収： プロピレングリコールを含まないため、筋肉内（IM）注射時に痛みを伴わず、迅速かつ確実に吸収されるため、IM投与においてジアゼパムより優れています。
- 逆説的興奮： 健康で不安のない犬や猫に単独で投与した場合、確実な鎮静が得られず、逆説的な不快感や興奮を引き起こすことがよくあります。他の薬剤（オピオイド、ケタミン、アルファ2作動薬など）と組み合わせて使用すると最も効果的です。
- てんかん重積状態： 活動性の発作を止めるのに非常に効果的であり、静脈内（IV）、筋肉内（IM）、または経鼻（IN）投与が可能です。
作用機序
Midazolam exerts its effects by enhancing the activity of gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the central nervous system.
- Target: Binds to specific allosteric benzodiazepine receptors on the GABA-A receptor complex.
- Mechanism: Binding increases the frequency of chloride channel openings → influx of chloride ions → hyperpolarization of the postsynaptic neuronal membrane → decreased neuronal excitability.
- Effects: This depression of subcortical levels (limbic, thalamic, and hypothalamic) produces anxiolytic, sedative, skeletal muscle relaxant, and anticonvulsant effects. Midazolam has approximately twice the affinity for benzodiazepine receptors compared to diazepam, making it more potent with a faster onset and shorter duration of action.
安全性・警告
禁忌
- Hypersensitivity to benzodiazepines
- Acute narrow-angle glaucoma
- Intra-carotid artery injection (must be avoided)
- Neonates (avoid use)
有害事象
- Respiratory depression (especially when combined with opioids or other CNS depressants)
- Paradoxical excitement, dysphoria, or agitation (especially in cats and dogs when used alone)
- Hypotension and bradycardia (when combined with other anesthetics like isoflurane or ketamine)
- Pain on injection or local irritation (rare compared to diazepam)
- Severe hypotension
- Paradoxical excitement (occasionally)
注意事項
High-Risk Patients: Use cautiously in patients with hepatic or renal disease, and in debilitated or geriatric patients.
- Cardiovascular/Respiratory: Administer with extreme caution to patients in coma, shock, or with significant respiratory depression. Patients with congestive heart failure may eliminate the drug more slowly.
- Anesthetic Combinations: While midazolam alone has minimal cardiorespiratory effects, combining it with opioids, ketamine, or inhalants can lead to significant respiratory depression, bradycardia, or hypotension.
- Pregnancy: FDA Category D in humans. May cause congenital abnormalities if used in the first trimester. Excreted in milk and may cause CNS effects in nursing neonates.
医薬品相互作用
Midazolam may decrease the dosages required for inhalant anesthetics.
May inhibit midazolam metabolism, increasing midazolam blood levels.
May increase midazolam levels.
May increase midazolam levels by inhibiting hepatic metabolism.
May increase the risk of profound sedation and respiratory depression.
May increase midazolam levels.
May increase the hypnotic effects of midazolam; hypotension has been reported when used with meperidine. Combination causes greater respiratory depression.
May decrease peak levels and AUC of midazolam via enzyme induction.
May decrease peak levels and AUC of midazolam.
Midazolam may decrease the dosages required for induction.
Potentiates effect, reducing the dose required for induction
Potentiates effect, reducing the dose required
May enhance the sedative effect
May enhance the sedative effect
May enhance the sedative effect
May increase the hypnotic and hypotensive effects of midazolam; enhances sedation
Inhibits the metabolism of midazolam
監視
- Level of sedation and central nervous system depression
- Respiratory rate, effort, and oxygenation (especially when combined with other drugs)
- Heart rate and blood pressure
- Respiratory rate and effort
- Heart rate and rhythm
- Level of sedation and consciousness
薬物動態
半減期
吸収
Following IM injection, midazolam is rapidly and nearly completely (91%) absorbed. Oral absorption is good, but bioavailability is low (31-72%) due to a rapid first-pass effect. Rectal bioavailability in dogs is very low. Intranasal administration (especially via compounded gel) provides good absorption and high peak levels.
分布
Highly protein bound (94-97%). Due to its high lipophilicity at physiologic pH, it rapidly crosses the blood-brain barrier. Changes in plasma protein concentrations can significantly alter the response to a given dose.
代謝
Metabolized in the liver, principally by microsomal oxidation. Forms an active metabolite (alpha-hydroxymidazolam), which has a very short half-life and negligible clinical effects.
消失
Eliminated primarily via hepatic metabolism and subsequent excretion. The duration of activity is considerably shorter than that of diazepam.
過剰投与
Accidental overdoses should be managed with supportive care (e.g., cardiovascular and respiratory support), similar to diazepam.
- Reversal Agent: Flumazenil is a specific benzodiazepine antagonist and can be used to reverse midazolam's effects.
- However, because midazolam has a very short duration of effect and flumazenil is costly, supportive therapy is usually sufficient for all but the most massive overdoses.
製品
製剤
- Injection (solution)
- Oral syrup
- Injectable solution: 1 mg/ml, 2 mg/ml, 5 mg/ml
- Oromucosal solution: 5 mg/ml (in 0.5 ml, 1 ml, 1.5 ml, 2 ml pre-filled syringes)
- Oromucosal solution: 10 mg/ml pre-filled syringe
動物用医薬品
- None (No veterinary-labeled products currently available)
- Buccolam
- Epistatus
- Hypnovel
ヒト用医薬品
- Midazolam HCl Injection: 1 mg/mL in 2 mL, 5 mL, 10 mL vials
- Midazolam HCl Injection: 5 mg/mL in 1 mL, 2 mL, 5 mL, 10 mL vials & 2 mL syringes
- Midazolam HCl Syrup: 2 mg/mL in 118 mL
- Buccolam
- Epistatus
- Hypnovel
規制ステータス
POM
POM-V
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store midazolam injection at room temperature (15°-30°C) and protect from light. It is physically stable after being frozen for 3 days and thawed. Midazolam is stable at a pH from 3-3.6. Compounded oral suspensions (e.g., with Syrpalta) retain >90% potency for 56 days when stored at 7°C, 20°C, or 40°C and protected from light.
飼主向け情報
注意： ミダゾラムは、ほぼ例外なく動物病院内、または専門家の直接の監督下でのみ投与されます。
- 目的： 手術前にリラックスさせたり、筋肉を弛緩させたり、起きている発作を素早く止めるために、ペットにこの薬が投与されることがあります。
- 行動の変化： 単独で投与された場合、一部のペット（特に健康な犬や猫）は、眠くなる代わりに一時的に落ち着きがなくなったり、鳴いたり、ふらついたりすることがあります。これはよく知られた反応であり、すぐに治まります。
- 安全性： 他の麻酔薬と組み合わせて使用すると呼吸や心拍数に影響を与える可能性があるため、薬が効いている間、獣医療チームがペットのバイタルサインを注意深く監視します。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。