ブプレノルフィン
ブプレノルフィンは、獣医療において広く使用されている**オピオイド部分アゴニスト**です。主に小動物の軽度から中等度の急性疼痛の管理に利用され、アルファ2アゴニストや解離性麻酔薬と組み合わせた短時間の不動化「カクテル」に組み込まれることがよくあります。 * **臨床上のポイント**: ブプレノルフィンは標準用量で「天井効果（シーリングエフェクト）」を示します。つまり、一定の用量を超えて増量しても追加の鎮痛効果は得られず、理論的には鎮痛効果が低下する可能性があります。 * **猫における利点**: 猫の口腔内pHは比較的アルカリ性であるため、ブプレノルフィンは高い脂溶性を示し、優れた**口腔粘膜（OTM）/ 頬粘膜吸収**を可能にします。猫では、頬粘膜投与のバイオアベイラビリティは筋肉内注射とほぼ同等であり、家庭での術後疼痛管理において非常に実用的な経路となります。 * **持続時間**: 純粋なミューアゴニスト（フェンタニルやメタドンなど）と比較して効果発現までの時間は長いですが、鎮痛効果の持続時間は著しく長くなります（通常6〜8時間、最大12時間）。 * **規制**: 本剤は規制薬物に指定されています。
作用機序: Buprenorphine exerts its analgesic effects by acting as a **partial agonist at the mu (μ) opioid receptor** and an **antagonist at the kappa (κ) opioid receptor** in the central nervous system. * **High Affinity, Slow Dissociation**: It binds to the μ-receptor with an affinity approximately 30 times greater than morphine. This tight binding → prolonged duration of action. * **Receptor Competition**: Because of its high affinity, it can displace pure μ-agonists from the receptor, potentially antagonizing their analgesic effects while reversing their sedative and respiratory depressant effects. * **Naloxone Resistance**: Its slow dissociation from the receptor makes it notoriously difficult to fully reverse with standard doses of the opioid antagonist **naloxone**; high doses of naloxone or the use of doxapram may be required in cases of severe respiratory depression.
動物種別の用量
- Analgesia · 0.005-0.02 mg/kg IM, IV or SC q6-12h · IM, IV, SC · q6-12h
- Analgesia · 2-4 micrograms/kg/hour · IV · continuous infusion
- Analgesia · 0.005-0.03 mg/kg IV, IM, SC, epidural · IV, IM, SC, epidural
- Analgesia · 0.006-0.02 mg/kg IV, IM, SQ · IV, IM, SQ · 6-12 hours · Relatively effective analgesic, but may be difficult to reverse with naloxone if untoward effects are seen.
- Analgesia · 0.02 mg/kg · IV, IM, SC · q6h · SC route is listed in historical dosing but text notes it is not recommended due to potentially lower efficacy compared to IM/IV.
- Analgesia · 0.01-0.05 mg/kg SC or IM 2-3 times daily · SC, IM · 2-3 times daily
- Analgesia · 0.01-0.03 mg/kg IM, IV, Buccal · IM, IV, Buccal · up to 6 hours · Buccal use is well accepted by cats.
- Analgesia · 0.01-0.03 mg/kg PO transmucosally (squirted directly into the mouth) q8h · PO transmucosal · q8h
- Analgesia · 0.01-0.03 mg/kg IM, IV, SC q6-8h; 0.01-0.03 mg/kg PO q6-12h · IM, IV, SC, PO · q6-12h
- Analgesia · 1-3 micrograms/kg/hour · IV · continuous infusion
投与経路
禁忌
- Known hypersensitivity to buprenorphine
有害事象
- Respiratory depression (rare but significant)
- Sedation
- Urine retention or difficulty voiding (particularly with high IV or epidural doses)
- Excitement (horses)
- Diminished gut sounds (horses)
- Vomiting (rare in cats)
薬物相互作用
- Local Anesthetics (mepivacaine, bupivacaine) · May be potentiated by concomitant use of buprenorphine
- Anticonvulsants (phenobarbital, phenytoin) · May decrease plasma buprenorphine levels
- Benzodiazepines · Case reports of humans developing respiratory/cardiovascular/CNS depression; use with caution
- CNS Depressants (anesthetics, antihistamines, phenothiazines, barbiturates, alcohol) · May cause increased CNS or respiratory depression when used with buprenorphine
- Erythromycin · Can increase plasma buprenorphine levels
- Fentanyl (and other pure opiate agonists) · Buprenorphine may potentially antagonize some analgesic effects, but may also reverse some sedative and respiratory depressant effects
- Halothane · Potentially can increase buprenorphine effects
- Azole Antifungals (ketoconazole, itraconazole, fluconazole) · Can increase plasma buprenorphine levels
- Monoamine Oxidase Inhibitors (selegiline, amitraz) · Possible additive effects or increased CNS depression
- Naloxone · May reduce analgesia associated with high dose buprenorphine
- Pancuronium · If used with buprenorphine may cause increased conjunctival changes
- Rifampin · Potentially decrease plasma buprenorphine concentrations
モニタリング
- Analgesic efficacy
- Respiratory status
- Cardiac status
過量投与
Buprenorphine has a very high index of safety (ratio of lethal dose to effective dose is at least 1000:1 in rodents). Life-threatening acute overdoses are rare in veterinary medicine, but clinical signs are common. * **Clinical Signs (Dogs)**: Vocalization, ataxia, hypersalivation, hypothermia, and lethargy. * **Treatment**: Supportive care. In cases of acute overdose causing severe respiratory or cardiac effects, **naloxone** and **doxapram** are suggested. > **Note**: Due to buprenorphine's extremely high affinity for the mu-receptor, standard doses of naloxone may be ineffective; very high doses of naloxone may be required to reverse respiratory depression.
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。