メトカルバモール
Methocarbamol
Guaiphenesin carbamate
別名: Robaxin-V · Robaxin-750 · Guaiphenesin carbamate · Labycarbol · Laxan · Lumirelax · Miowas · Musxan · Myocin · Myomethol · Ortoton · Remisol · Rexivin · Robinax · Traumacut · Methocarbamolum
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
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。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Relief of moderate conditions | 44 mg/kg IV | IV | As directed | — | 🌎 NA |
| Controlling severe effects of strychnine and tetanus | 55-220 mg/kg IV | IV | As directed | — | 🌎 NA |
| General muscle relaxation (Tablets) | Initially, 132 mg/kg/day PO divided q8h-q12h, then 61-132 mg/kg divided q8-12h | PO | q8h-q12h | Discontinue if no response in 5 days | 🌎 NA |
| Muscle relaxation for intervertebral disk disease (IVDD) | 15-20 mg/kg PO three times daily | PO | TID | — | 🌎 NA |
| Muscle relaxation for certain toxicosis (e.g., strychnine, metaldehyde, tetanus) | 150 mg/kg IV | IV | As directed | — | 🌎 NA |
| Control severe tremors associated with tremorgenic Mycotoxin intoxication | 55-220 mg/kg IV to effect at a rate no more than 2 mL/minute | IV | As directed | — | 🌎 NA |
| Control tremors associated with Guarana (caffeine) toxicity | 50-220 mg/kg IV, administered slowly and to effect; do not exceed 330 mg/kg/day | IV | As directed | — | 🌎 NA |
| General muscle spasms, tetanus, toxicities | 20-45 mg/kg | PO | q8h | As needed | 🌍 EU |
- Relief of moderate conditions: Administer half the estimated dose rapidly, then wait until animal starts to relax and continue administration to effect.
- Controlling severe effects of strychnine and tetanus: Do not exceed 330 mg/kg/day. Administer half the estimated dose rapidly, then wait until animal starts to relax and continue administration to effect.
- General muscle spasms, tetanus, toxicities: Very high doses may be required for tetanus. Recommended not to exceed 330 mg/kg.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Relief of moderate conditions | 44 mg/kg IV | IV | As directed | — | 🌎 NA |
| Controlling severe effects of strychnine and tetanus | 55-220 mg/kg IV | IV | As directed | — | 🌎 NA |
| General muscle relaxation (Tablets) | Initially, 132 mg/kg/day PO divided q8h-q12h, then 61-132 mg/kg divided q8-12h | PO | q8h-q12h | Discontinue if no response in 5 days | 🌎 NA |
| Adjunctive treatment (control of seizures/muscle tremors) of permethrin toxicity | initially administered at 50-150 mg/kg IV | IV | As directed | — | 🌎 NA |
| General muscle spasms, tetanus, toxicities | 20-45 mg/kg | PO | q8h | As needed | 🌍 EU |
- Relief of moderate conditions: Administer half the estimated dose rapidly, then wait until animal starts to relax and continue administration to effect.
- Controlling severe effects of strychnine and tetanus: Do not exceed 330 mg/kg/day. Administer half the estimated dose rapidly, then wait until animal starts to relax and continue administration to effect.
- Adjunctive treatment (control of seizures/muscle tremors) of permethrin toxicity: First half is given IV slowly over approximately 5-10 minutes and the second half of the dose being given as needed to effect. The dose can be repeated up to a maximum of 330 mg/kg/day; in severely affected cases, the total daily dose can be calculated and given over 24 hours as a constant rate infusion.
- General muscle spasms, tetanus, toxicities: Very high doses may be required for tetanus. Recommended not to exceed 330 mg/kg. Limited literature in cats.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Moderate conditions | 4.4-22 mg/kg IV to effect | IV | As directed | — | 🌎 NA |
| Severe conditions | 22-55 mg/kg IV | IV | As directed | — | 🌎 NA |
| General muscle relaxation | 15-25 mg/kg IV by slow infusion | IV | As directed | — | 🌎 NA |
| Oral administration | Use 2-3 times the recommended IV dose | PO | As directed | — | 🌎 NA |
| Acute rhabdomyolysis | 15-25 mg/kg slow IV infusion | IV | May repeat up to four times daily if needed | — | 🌎 NA |
- Moderate conditions: ARCI UCGFS Class 4 Drug
牛
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Treatment of CNS hyperactivity | 110 mg/kg IV | IV | As directed | — | 🌎 NA |
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
メトカルバモールは、グアイフェネシンに構造的に関連する中枢性骨格筋弛緩薬です。獣医学において、骨格筋の急性炎症や外傷性疾患の治療、および重度の筋肉のけいれんや振戦の管理に広く使用されています。
臨床上のポイント:
- 猫のペルメトリン中毒や犬の振戦誘発性マイコトキシン（カビの生えた食品など）中毒に対する救命処置として非常に有効であり、頻繁に使用されます。
- 経口および注射の両方の製剤が利用可能です。
- 注射剤にはポリエチレングリコール（PEG）300が含まれており、既存の腎病変を悪化させる可能性があるため、重度の腎疾患を持つ患者には静脈内投与を慎重に行うか避けるべきです。
- 収縮した骨格筋を直接弛緩させるのではなく、中枢神経系の抑制を介して作用します。
作用機序
The exact mechanism of action of methocarbamol is not fully understood, but it is known to act centrally rather than peripherally.
- Central CNS Depression: It is believed to cause skeletal muscle relaxation by general central nervous system depression, likely depressing polysynaptic reflexes in the internuncial neurons of the spinal cord.
- No Peripheral Action: It has no direct relaxant effects on striated muscle, nerve fibers, or the motor endplate.
- Secondary Effects: Produces a secondary sedative effect due to its generalized CNS depressant properties.
安全性・警告
禁忌
- Food-producing animals
- Renal disease (injectable formulation only, due to PEG 300 vehicle)
- Known hypersensitivity to methocarbamol
- Subcutaneous (SC) administration
- No specific contraindications available, but use with caution in renal or hepatic impairment.
有害事象
- Sedation
- Salivation
- Emesis
- Lethargy
- Weakness
- Ataxia
注意事項
Administration Warnings:
- Intravenous Use: Give IV slowly. Do not exceed a rate of 2 mL/minute in dogs and cats. Avoid extravasation as it can cause tissue irritation.
- Do NOT administer subcutaneously (SC).
Organ System Warnings:
- Renal Impairment: The injectable product contains polyethylene glycol (PEG) 300, which can increase pre-existing acidosis and urea retention. Avoid IV use in patients with known or suspected renal pathology.
- Working Animals: May impair the abilities of working animals due to CNS depressant effects.
Reproductive/Nursing:
- FDA Category C for pregnancy. Use with caution as a last resort when benefits clearly outweigh risks. Safety during lactation is unknown, though considered compatible with breastfeeding in humans.
Laboratory Considerations:
- May falsely elevate urinary values of vanillylmandelic acid (VMA) or 5-HIAA.
医薬品相互作用
Additive CNS depression may occur when given concurrently.
May cause severe weakness (reported in a human patient with myasthenia gravis).
Additive CNS depression
監視
- Level of muscle relaxation
- Degree of sedation
- Respiratory rate and effort (especially with high IV doses or concurrent CNS depressants)
- Degree of muscle relaxation
- CNS depression/sedation levels
- Renal and hepatic function (if prolonged use)
薬物動態
半減期
吸収
In humans, onset of action is about 30 minutes after oral administration. Peak levels occur approximately 2 hours after dosing.
分布
Limited pharmacokinetic data is available in veterinary species.
代謝
The drug is metabolized to inactive metabolites. Guaifenesin is a minor metabolite of methocarbamol, but due to very low concentrations, it likely has no clinical effect.
消失
Inactive metabolites are excreted primarily into the urine, with small amounts in the feces. In horses, plasma clearances appear to be dose-dependent after IV administration (lower clearances measured after higher doses).
過剰投与
Signs of Toxicity: Overdosage is generally characterized by profound CNS depressant effects, including loss of righting reflex and prostration. Excessive doses in dogs and cats may manifest as emesis, salivation, severe weakness, and ataxia.
Management:
- Decontamination: If the overdose occurred recently via oral administration, emptying the gut (e.g., emesis induction or gastric lavage) may be indicated. Do not induce emesis if the patient's continued consciousness and airway protection are not assured.
- Supportive Care: Treat other clinical signs supportively if severe. Monitor respiratory and cardiovascular function closely.
製品
製剤
- Injection
- Oral: 500 mg, 750 mg tablets
動物用医薬品
- Methocarbamol Tablets: 500 mg (Robaxin-V)
- Methocarbamol Injection: 100 mg/mL in vials of 20 mL and 100 mL (Robaxin-V)
ヒト用医薬品
- Methocarbamol Tablets: 500 mg & 750 mg (Robaxin, Robaxin-750, generic)
- Methocarbamol Injection: 100 mg/mL in 10 mL vials (Robaxin)
- Robaxin 500 mg tablets
- Robaxin 750 mg tablets
規制ステータス
POM (Prescription Only Medicine)
POM
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store tablets at room temperature in tight containers. Store the injection at room temperature and do not freeze. Solutions prepared for IV infusion should not be refrigerated as a precipitate may form. Because a haze or precipitate may form, all diluted intravenous solutions should be physically inspected before administration.
飼主向け情報
重要な注意事項: この薬を服用している間、ペットの尿の色が濃くなる（黒、茶色、または緑色に見えることがあります）ことがあります。これは無害な副作用であり、心配する必要はありません。
- 鎮静と運動失調: この薬は通常、眠気、無気力、および歩行の不調和（運動失調）を引き起こします。怪我を防ぐため、ペットを階段や飛び降りる可能性のある家具、その他の危険から遠ざけ、安全で限られた場所に置いてください。
- 投与: 処方通りに正確に投与してください。1回分を飲み忘れた場合でも、次回の投与で2回分を一度に与えないでください。
- 報告すべき副作用: ペットに重度の嘔吐、過度のよだれ、または立てないほどの衰弱が見られた場合は、獣医師に連絡してください。
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