メトカルバモール
**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.
動物種別の用量
- Relief of moderate conditions · 44 mg/kg IV · IV · As directed · 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 · 55-220 mg/kg IV · IV · As directed · 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 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
- Adjunctive treatment (control of seizures/muscle tremors) of permethrin toxicity · initially administered at 50-150 mg/kg IV · IV · As directed · 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 · 20-45 mg/kg · PO · q8h · As needed · Very high doses may be required for tetanus. Recommended not to exceed 330 mg/kg. Limited literature in cats.
- Moderate conditions · 4.4-22 mg/kg IV to effect · IV · As directed · ARCI UCGFS Class 4 Drug
- Severe conditions · 22-55 mg/kg IV · IV · As directed
- General muscle relaxation · 15-25 mg/kg IV by slow infusion · IV · As directed
投与経路
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
薬物相互作用
- CNS Depressants (e.g., opioids, benzodiazepines, barbiturates) · Additive CNS depression may occur when given concurrently.
- Pyridostigmine · May cause severe weakness (reported in a human patient with myasthenia gravis).
- Other CNS depressants · Additive CNS depression · moderate
モニタリング
- 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)
過量投与
**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.
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。