哌替啶
哌替啶(又稱 pethidine)是一種合成的**鴉片類促效劑**,主要用於鎮痛。 **臨床要點:** * 雖然過去很受歡迎,但由於其作用時間極短(在犬貓體內小於 1-2 小時),且極易引起**組織胺釋放**和低血壓(特別是靜脈注射時),其在現代獸醫學中的使用已大幅減少。 * 與大多數其他鴉片類藥物不同,哌替啶具有**抗膽鹼(迷走神經抑制)和負性肌力作用**,這可能導致心跳過速,而非純 mu 促效劑常見的心跳過緩。 * 其效力約為嗎啡的 1/3 至 1/8,但在等效鎮痛劑量下會產生同等程度的呼吸抑制。 * 本品為第二級管制藥品(C-II)。
作用機制: Meperidine acts primarily as an agonist at the **mu (μ) opioid receptors** in the central nervous system (CNS) and peripheral tissues. * **Receptor Binding:** Binds to G-protein coupled mu receptors → inhibits adenylate cyclase → decreases intracellular cAMP. * **Ion Channel Modulation:** Promotes opening of potassium channels (causing hyperpolarization) and inhibits voltage-gated calcium channels (decreasing neurotransmitter release). * **Analgesia:** Inhibits ascending nociceptive pathways and alters the perception of pain. * **Unique Mechanisms:** Exhibits **anticholinergic (vagolytic)** effects and can cause direct mast cell degranulation leading to **histamine release**.
各物種劑量
- Perioperative pain · 3-5 mg/kg · IM, SC · 1-2 hours
- Analgesia · 2-5 mg/kg · IM, SC · short (30 minutes to an hour)
- Pre-medication · 3-4 mg/kg · IM · In healthy cats
- Post-op analgesia · 1-2 mg/kg · IM · In healthy cats
- General Note · Not recommended for cats
- Analgesia (mild to moderate pain) · 5-10 mg/kg · IM, SC · q1-2h · Depending on pain assessment · Frequent redosing is required.
- Restraining agent (preanesthetic) · 1-2 mg/kg · IM · 45-60 minutes before anesthesia · Used in combination with promazine (2 mg/kg IM) and atropine (0.07-0.09 mg/kg IM) in separate sites.
- Analgesia · 2 mg/kg · IM · q4h · as needed
- Analgesia · 5-10 mg/kg · SC, IM · q2-3h
- Analgesia · Up to 200 mg total dose · IM
給藥途徑
禁忌症
- Hypersensitivity to narcotic analgesics
- Patients receiving monamine oxidase inhibitors (MAOIs)
- Diarrhea caused by a toxic ingestion (until toxin is eliminated)
- Envenomations from Centruroides scorpion species, Gila monsters, or Mexican beaded lizards
- Intravenous (IV) administration
- Animals at risk from histamine release (e.g., skin allergies, asthma, mast cell tumours)
不良反應
- Respiratory depression
- Histamine release
- Bronchoconstriction (dogs)
- CNS depression
- Nausea and vomiting
- Decreased intestinal peristalsis
- Mydriasis (dogs)
- Salivation (especially cats)
- Physical dependence (chronic use)
- Tachycardia with PVCs (horses)
- Profuse sweating (horses)
- Hyperpnea (horses)
- Severe hypotension (if given IV rapidly)
- Hypotension (especially if given IV)
- Tachycardia
- Bronchoconstriction
藥物相互作用
- CNS Depressants (anesthetics, antihistamines, phenothiazines, barbiturates, tranquilizers) · May cause increased CNS or respiratory depression when used with meperidine.
- Diuretics · Opiates may decrease efficacy in CHF patients.
- Isoniazid · Meperidine may enhance INH adverse effects.
- Monamine Oxidase Inhibitors (MAOIs) (e.g., amitraz, selegiline) · Contraindicated. Can cause severe opiate overdose signs; avoid meperidine for at least 14 days after receiving MAOIs.
- Skeletal Muscle Relaxants · Meperidine may enhance neuromuscular blockade.
- Tricyclic Antidepressants (clomipramine, amitriptyline) · Meperidine may exacerbate the effects of tricyclic antidepressants.
- Warfarin · Opiates may potentiate anticoagulant activity.
- CNS depressants (anaesthetics, antihistamines, barbiturates, phenothiazines, tranquillizers) · Increased CNS or respiratory depression · moderate
- Monoamine oxidase inhibitors (MAOIs) · Serious interaction resulting in coma, convulsions, and hyperpyrexia · major
監測
- Respiratory rate and depth
- CNS level of depression or excitation
- Blood pressure (especially with IV use)
- Analgesic activity
- Pain score
- Heart rate
- Blood pressure
- Signs of histamine release (urticaria, bronchoconstriction)
過量
Overdosage may produce profound **respiratory and/or CNS depression**. Other effects can include cardiovascular collapse, hypothermia, and skeletal muscle hypotonia. * **Species Differences:** Some species (especially cats) may demonstrate CNS excitability (hyperreflexia, tremors) and seizures at doses >20 mg/kg. * **Treatment:** **Naloxone** is the agent of choice for respiratory depression. In massive overdoses, naloxone doses may need to be repeated, as its effects can diminish before subtoxic levels of meperidine are attained. Mechanical respiratory support should be considered. Pentobarbital has been suggested for CNS excitement/seizures in cats, but extreme caution is required as barbiturates and narcotics have additive respiratory depressant effects.
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