氫嗎啡酮
氫嗎啡酮是一種強效的半合成**純μ-鴉片受體促效劑**，在獸醫學中廣泛用作鎮靜劑、保定劑、鎮痛藥和麻醉前用藥。 主要臨床特徵包括： - **效力**：按重量計算，其效力約為嗎啡的5倍，與羥嗎啡酮（oxymorphone）大致相當。 - **優於嗎啡之處**：通常鎮靜作用較輕，靜脈注射後引起的組織胺釋放極少，且極少引起顯著的血管擴張或低血壓。 - **臨床實用性**：由於鎮痛效果和作用時間與羥嗎啡酮相似，但成本顯著較低，在獸醫臨床上正迅速取代羥嗎啡酮。 - **管制狀態**：由於具有高度濫用和生理依賴潛力，屬於**第二級（C-II）**管制藥品。
作用機制: Hydromorphone exerts its effects by binding to opioid receptors, primarily the **mu (μ) receptors**, with some affinity for **delta (δ) receptors**. Mechanism pathway: Agonist binding to **mu-receptors** in the CNS (limbic system, spinal cord, thalamus, midbrain) and peripheral tissues (GI tract, smooth muscle) → activation of G-proteins → inhibition of **adenylate cyclase** → decreased intracellular cAMP → opening of **potassium channels** (causing hyperpolarization) and closing of **voltage-gated calcium channels** → decreased presynaptic release of excitatory neurotransmitters (e.g., **Substance P**, glutamate) → profound **analgesia** and altered pain perception. Secondary effects include respiratory depression (decreased sensitivity of the respiratory center to CO2), antitussive activity, and increased GI sphincter tone leading to decreased motility.
各物種劑量
- As an analgesic · 0.05-0.1 mg/kg IM, IV or SC q2-6 hours · IM/IV/SC · q2-6h
- For cancer pain · 0.08-0.2 mg/kg IV, IM, or SC · IV/IM/SC · Not specified
- For moderate to severe pain · 0.08-0.3+ mg/kg IV, IM or SC q2-6 hours · IV/IM/SC · q2-6h
- As a premed prior to moderately painful procedures · 0.1 mg/kg · Not specified · Once · May be combined with acepromazine (0.05-0.2 mg/kg) in young, healthy patients.
- As an alternate induction method (especially in critical patients) · 0.05-0.2 mg/kg IV, slowly to effect followed by diazepam 0.02 mg/kg IV · IV · Once · Do not mix two drugs together. Positive pressure ventilation likely necessary.
- As a pre-op · 0.05-0.1 mg/kg IV · IV · Once
- As a CRI post-op · 0.05 mg/kg IV loading dose, then 0.05-0.1 mg/kg/hr · IV · CRI
- As a pre-op (Rabbits) · 0.05-0.1 mg/kg IV · IV · Once
- As a CRI post-op (Rabbits) · 0.05 mg/kg IV loading dose, then 0.05-0.1 mg/kg/hr · IV · CRI
給藥途徑
禁忌症
- Hypersensitivity to narcotic analgesics
- Diarrhea caused by toxic ingestion (until toxin is eliminated)
- Prior to GI obstructive surgery (due to vomiting risk)
- Patients stung by scorpion species Centruroides sculpturatus Ewing and C. gertschi Stahnke (may potentiate venom)
不良反應
- Dogs: Nausea, vomiting, defecation, panting, vocalization, sedation, CNS depression, respiratory depression, bradycardia, decreased GI motility (constipation with chronic use)
- Cats: Nausea, ataxia, hyperesthesia, hyperthermia, behavioral changes (mania/excitement if given without tranquilization)
- Mild histamine release (infrequent compared to morphine)
藥物相互作用
- Butorphanol, Nalbuphine · Potentially could antagonize opiate effects
- CNS Depressants · Additive CNS depression effects possible
- Diuretics · Opiates may decrease diuretic efficacy in CHF patients
- Monoamine Oxidase Inhibitors (e.g., amitraz, selegiline) · Severe and unpredictable opiate potentiation; not recommended if MAOI used within 14 days
- Skeletal Muscle Relaxants · Hydromorphone may enhance muscle relaxant effects
- Phenothiazines · May antagonize analgesic effects and increase risk for hypotension
- Tricyclic Antidepressants (clomipramine, amitriptyline) · Hydromorphone may exacerbate the effects of tricyclic antidepressants
- Warfarin · Opiates may potentiate anticoagulant activity
監測
- Respiratory rate and depth (pulse oximetry highly recommended)
- CNS level of depression or excitation
- Blood pressure (especially with IV use)
- Cardiac rate (monitor for bradycardia)
- Analgesic efficacy
過量
Massive overdoses may produce profound **respiratory and/or CNS depression** in most species. Other potential effects include: - Cardiovascular collapse - Hypothermia - Skeletal muscle hypotonia - Mania (especially in cats) **Treatment**: - **Naloxone** is the specific reversal agent of choice for treating respiratory depression. - In massive overdoses, naloxone doses may need to be repeated, as naloxone's duration of action may be shorter than that of hydromorphone. - Mechanical respiratory support should be considered in cases of severe respiratory depression. - Provide supportive care as needed.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。