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モルヒネ

Morphine

Morphine sulfate

オピオイド作動薬 / 鎮痛薬IVIMSCEpiduralSpinalIntra-articularPORectal犬猫小型哺乳類馬豚羊ヤギ

別名: Astramorph PF · Avinza · DepoDur · Infumorph · Kadian · MSIR · MS Contin · Oramorph SR · RMS · Roxanol · Morphini sulfas · Morphine sulfate · Morphine 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

構造化された用量計算エビデンス

Analgesia (extra-label) — CRI dosing

0.05–0.1 mg/kg/mg/kg/hIV

認証済み獣医師の確認が必要

NA

必ず考慮する臨床コンテキスト (5)
  • 1. Preservative-free morphine formulations should be used for epidural administration.
  • 2. Do not confuse CRI dosages listed as mg/kg/hour with those listed as µg/kg/minute.
  • 3. For additional dosages/protocols for using morphine in combination with other drugs (eg, ketamine, lidocaine, dexmedetomidine) for pain/sedation in dogs or cats, see the dosages and their accompanying references in the Dexmedetomidine, Ketamine, and Lidocaine monographs.
  • Analgesia (extra-label):
  • Morphine injection should be stored at room temperature (20°C-25°F [68°F-77°F]), protected from light; do not freeze. 19 Morphine gradually darkens in color when exposed to light. Morphine does not appear to adsorb to plastic or polyvinyl chloride (PVC) syringes, tubing, or bags.
規制薬認証済み獣医師の確認が必要formularyプロトコル 2023監査 dose-audit-plumb-v13

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。

診察中ですか？VetSheet の AI が薬剤・用量・投与期間を構造化された診察記録に直接記入します。VetSheet の仕組みを見る

概要

モルヒネは、獣医学において中等度から重度の急性疼痛の治療に使用される代表的な​オピオイド鎮痛薬​です。アヘン由来の天然の純粋なμ（ミュー）オピオイド受容体作動薬です。

​臨床上のポイントと種差：​

  • ​犬および霊長類：​ モルヒネは通常、予測可能な中枢神経系の抑制、鎮静、および鎮痛を引き起こします。化学受容器引き金帯（CTZ）を直接刺激するため、犬に対しては強力な催吐薬となります。犬は初回投与直後に排便することが多く、その後消化管の運動が低下します。
  • ​猫、馬、反芻動物：​ これらの種では、特に鎮静剤や精神安定剤（アセプロマジンやα2作動薬など）を併用せずに投与した場合、抑制ではなく逆説的な​中枢神経系の興奮​（不快気分、躁状態、常同歩行）を示すことがあります。猫で嘔吐を誘発するには、犬よりもはるかに高用量が必要です。
  • ​ヒスタミン遊離：​ モルヒネは肥満細胞から非免疫学的なヒスタミン遊離を引き起こします。重度の低血圧、血管拡張、気管支収縮を避けるため、静脈内投与はゆっくりと行う必要があります。
  • ​体温調節：​ モルヒネは犬やウサギでは低体温を引き起こす可能性がありますが、猫、馬、牛、ヤギでは高体温を引き起こします。

作用機序

Morphine acts primarily as a full agonist at the mu (μ) opioid receptors in the central nervous system, with some secondary activity at delta receptors.

  • ​Mechanism:​ Binding to the G-protein coupled mu-receptor → inhibits adenylate cyclase → decreases intracellular cAMP.
  • ​Presynaptic effect:​ Closes voltage-gated calcium channels → decreases the release of excitatory nociceptive neurotransmitters (e.g., Substance P, glutamate).
  • ​Postsynaptic effect:​ Opens inward-rectifying potassium channels → hyperpolarizes the neuron → inhibits ascending pain transmission pathways.
  • ​Secondary effects:​ Direct stimulation of the ​chemoreceptor trigger zone (CTZ)​ causes emesis. Central vagal stimulation leads to bradycardia. Increased anti-diuretic hormone (ADH) release can reduce urine production.

安全性・警告

禁忌

  • Hypersensitivity to narcotic analgesics
  • Patients receiving monoamine oxidase inhibitors (MAOIs)
  • Diarrhea caused by a toxic ingestion (until toxin is eliminated)
  • Scorpion envenomation (Centruroides spp. - potentiates venom)
  • Conditions where vomiting is contraindicated (e.g., raised intraocular pressure)

有害事象

  • Histamine release (hypotension, vasodilation)
  • Bronchoconstriction
  • CNS depression (dogs, primates) or excitation (cats, horses, ruminants)
  • Physical dependence (with chronic use)
  • Hyperthermia (cattle, goats, horses, cats)
  • Hypothermia (dogs, rabbits)
  • Nausea and vomiting
  • Decreased intestinal peristalsis and constipation
  • Initial defecation (dogs)
  • Panting (dogs)
  • Bradycardia or tachycardia
  • Histamine release (if given rapidly IV)
  • Vomiting (common in non-painful pre-operative patients)
  • Transient excitation (IV administration)
  • Respiratory depression (especially under general anaesthesia)
  • Constriction of gastrointestinal sphincters (e.g., pyloric sphincter)
  • Reduction in gastrointestinal motility (with prolonged use)
  • Neonatal sedation (crosses the placenta)

注意事項

​Extreme Caution:​ Patients with head injuries, increased intracranial pressure, acute abdominal conditions (e.g., colic - may mask clinical signs), and respiratory disease or acute respiratory dysfunction.

​Caution:​ Hypothyroidism, severe renal insufficiency (acute uremia), adrenocortical insufficiency (Addison's), and geriatric or severely debilitated patients.

​Important Notes:​

  • ​IV Administration:​ Must be given slowly to avoid significant hypotension and histamine release.
  • ​Envenomation:​ Avoid in envenomation situations, as clinical signs associated with histamine-release can be confused with anaphylaxis.
  • ​Uremia:​ Because of its effects on vasopressin (ADH), urine flow can decrease by up to 90% in dogs given large doses.

医薬品相互作用

CNS Depressants (anesthetics, antihistamines, phenothiazines, barbiturates)

May cause increased CNS or respiratory depression when used with morphine.

Diuretics

Opiates may decrease diuretic efficacy in congestive heart failure patients.

Monoamine Oxidase Inhibitors (MAOIs, e.g., amitraz, selegiline)

Use with extreme caution; contraindicated in humans due to risk of severe opiate overdose signs.

Skeletal Muscle Relaxants

Morphine may enhance neuromuscular blockade.

Tricyclic Antidepressants (clomipramine, amitriptyline)

Morphine may exacerbate the effects of tricyclic antidepressants.

Warfarin

Opiates may potentiate anticoagulant activity.

CNS depressants (anaesthetics, antihistamines, barbiturates, phenothiazines, tranquillizers)Major

Increased CNS or respiratory depression

監視

  • CNS level of depression or excitation
  • Blood pressure (especially with IV use)
  • Analgesic activity
  • Respiratory rate and depth (especially under general anaesthesia)
  • Pain scores (to assess individual efficacy)
  • Signs of histamine release (hypotension, tachycardia) during IV administration
  • Gastrointestinal motility

薬物動態

半減期

猫~3 hours馬88 minutes (IV)犬~1 hour

吸収

Absorbed when given by IV, IM, SC, and rectal routes. Very low oral bioavailability (<20%) in dogs due to a high first-pass effect, limiting the clinical usefulness of oral morphine in canines.

分布

Concentrates in the kidney, liver, and lungs; lower levels are found in the CNS. The majority of free morphine is found in skeletal muscle. Crosses the placenta and distributes into maternal milk. Volume of distribution in dogs is ~7.5 L/kg.

代謝

Major route of elimination is by metabolism in the liver, primarily by glucuronidation. Cats are deficient in this metabolic pathway, leading to prolonged half-lives.

消失

The active glucuronidated metabolite (M6G) is excreted by the kidney. Clearance in dogs is approximately 83 mL/min/kg.

過剰投与

​Signs of Toxicity:​ Overdosage may produce profound respiratory and/or CNS depression in most species. Newborns are more susceptible. Parenteral doses >100 mg/kg are thought to be fatal in dogs. Other toxic effects include cardiovascular collapse, hypothermia, and skeletal muscle hypotonia. Horses, cats, swine, and cattle may demonstrate CNS excitability (hyperreflexia, tremors) and seizures at high doses or if given rapidly intravenously.

​Treatment:​

  • Naloxone is the agent of choice for treating respiratory depression. Doses may need to be repeated as naloxone's effects might diminish before sub-toxic levels of morphine are attained.
  • Mechanical respiratory support should be considered in severe cases.
  • Pentobarbital has been suggested for CNS excitement and seizures in cats, but extreme caution is required as barbiturates and narcotics have additive respiratory depressant effects.

製品

製剤

  • Morphine Sulfate for Injection (1-50 mg/mL)
  • Liposomal Extended-release Injection (10 mg/mL)
  • Preservative-free Injection (0.5-25 mg/mL)
  • Soluble Tablets for Injection
  • Oral Tablets (15 mg, 30 mg)
  • Extended/Controlled Release Tablets (15-200 mg)
  • Extended/Sustained Release Capsules (20-200 mg)
  • Oral Solution (2-20 mg/mL)
  • Rectal Suppositories (5-30 mg)
  • Injectable solution: 10 mg/ml, 15 mg/ml, 20 mg/ml, 30 mg/ml
  • Oral tablets: 10 mg, 30 mg, 60 mg, 100 mg
  • Oral suspensions
  • Slow-release capsules
  • Granules

ヒト用医薬品

  • Morphine Sulfate for Injection (1 mg/mL to 50 mg/mL)
  • Morphine Sulfate Liposomal Extended-release Injection (DepoDur, 10 mg/mL)
  • Morphine Sulfate for Injection, preservative-free (Infumorph, Astramorph PF, 0.5 mg/mL to 25 mg/mL)
  • Morphine Sulfate Soluble Tablets for Injection (10 mg, 15 mg, 30 mg)
  • Morphine Sulfate Oral Tablets (15 mg, 30 mg)
  • Morphine Sulfate Extended/Controlled Release Tablets (MS Contin, Oramorph SR, 15 mg to 200 mg)
  • Morphine Sulfate Extended/Sustained Release Capsules (Avinza, Kadian, 20 mg to 200 mg)
  • Morphine Sulfate Oral Solution (MSIR, Roxanol, 2 mg/mL to 20 mg/mL)
  • Morphine Sulfate Rectal Suppositories (RMS, 5 mg to 30 mg)
  • Morphine sulfate injectable solutions
  • Morphine sulfate tablets and slow-release capsules
  • Morphine suppositories

規制ステータス

European Union✗ 未承認処方箋医薬品 · Schedule 2EMA

Methadone is the licensed alternative preferred for bolus administration.

United Kingdom✗ 未承認処方箋医薬品 · POM CD SCHEDULE 2VMD

Controlled Drug Schedule 2. Methadone is the licensed alternative.

規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

保管・安定性

Oral morphine products should be stored in tight, light-resistant containers at room temperature unless otherwise labeled. Morphine injection should be stored at room temperature, protected from light; do not freeze. Morphine gradually darkens in color when exposed to light; protect from prolonged exposure to bright light.

飼主向け情報

モルヒネは強力で厳しく規制されている鎮痛薬であり、通常は獣医師の直接の監督下で病院内で投与されます。

  • ​予想されること：​ ペットは鎮静状態になり、眠そうにしたり、異常に静かになったりすることがあります。犬は激しくパンティング（あえぎ呼吸）をすることが多く、投与直後に嘔吐や排便をすることがあります。
  • ​猫と馬：​ 眠そうにするのではなく、落ち着きがなくなったり、歩き回ったり、目を大きく見開いたりすることがあります。これは知られている種差です。
  • ​自宅でのケア：​ 経口モルヒネを自宅に持ち帰る場合は、子供や他の動物の手の届かないところに厳重に保管してください。これは高度に規制されている薬物（スケジュールII）です。獣医師に相談せずに用量を変更しないでください。

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