金剛胺鹽酸鹽
**金剛胺 (Amantadine)** 最初是作為預防和治療A型流感的抗病毒藥物開發的，但在現代獸醫學中，它主要被利用其 **NMDA（N-甲基-D-天冬氨酸）受體拮抗劑** 的特性。 主要臨床應用包括： * **輔助鎮痛**：主要用於犬貓治療慢性、神經病理性或對鴉片類藥物產生耐受性的疼痛（例如嚴重的骨關節炎、骨肉瘤）。它很少作為單一鎮痛劑發揮作用，但與非類固醇抗發炎藥 (NSAIDs)、鴉片類藥物或加巴噴丁 (Gabapentin) 併用時，能有效對抗中樞敏感化。 * **馬流感**：曾被研究用於馬-2型流感病毒，但由於成本高、口服吸收不穩定以及靜脈注射有引發癲癇的風險，臨床使用受到限制。 > **臨床要點**：金剛胺是治療「痛覺纏繞 (wind-up pain)」（觸發痛和痛覺過敏）的關鍵藥物，適用於神經系統對疼痛訊號變得過度敏感的情況。
作用機制: Amantadine has distinct mechanisms depending on the therapeutic target: * **Analgesia (NMDA Antagonism)**: Chronic pain causes excessive release of excitatory neurotransmitters (glutamate and aspartate). These bind to the **NMDA receptor** on postsynaptic neurons in the dorsal horn of the spinal cord. Amantadine acts as a non-competitive antagonist, blocking the open ion channel of the **NMDA receptor** → prevents calcium (Ca2+) influx → reduces central sensitization and "wind-up" pain. * **Antiviral**: Interferes with the **influenza A virus M2 transmembrane protein** → blocks the uncoating of the virus particle and prevents viral replication. * **Antiparkinsonian (Human)**: Potentiates dopaminergic neurotransmission in the CNS and exhibits mild anticholinergic activity.
各物種劑量
- Osteoarthritis pain when NSAIDs alone are not effective · 3-5 mg/kg PO once daily in addition to an NSAID · PO · q24h · Meloxicam at approved doses was used for this study.
- Adjunctive therapy for chronic pain · 3-5 mg/kg PO once daily · PO · q24h
- To decrease wind-up · 3-5 mg/kg PO once daily for one week · PO · q24h · 1 week
- Analgesia (adjunct for chronic pain) · 3-5 mg/kg · PO · sid to bid · Chronic · Potentiates the effects of other analgesics. Often combined with NSAIDs.
- Adjunctive therapy for chronic pain · 3 mg/kg PO once daily · PO · q24h · May be useful addition to NSAIDs; has not been evaluated for toxicity. May need to be compounded.
- Adjunctive therapy for chronic pain · 3-5 mg/kg PO once daily · PO · q24h
- Adjunctive therapy for chronic pain · 3 mg/kg PO once daily · PO · q24h
- Analgesia (adjunct for chronic pain) · 3-5 mg/kg · PO · sid · Chronic · Liquid formulations may be bitter and difficult to administer.
- Acute treatment of equine-2 influenza · 5 mg/kg IV q4h · IV · q4h · Not commonly used due to expense, PK variability, and seizure risk.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Known hypersensitivity to amantadine or rimantadine
- Untreated angle-closure glaucoma
- Extra-label use in chickens, turkeys, and ducks (Prohibited by FDA)
不良反應
- Agitation or restlessness (especially early in therapy)
- Loose stools, flatulence, or diarrhea
- Narrow safety margin in cats (potential for neurotoxicity)
- Seizures (reported in horses given IV)
藥物相互作用
- Anticholinergic drugs · May enhance the anticholinergic effects of amantadine.
- CNS Stimulants (e.g., selegiline) · Concomitant use may increase the CNS stimulatory effects of amantadine.
- Trimethoprim/sulfa, quinidine, quinine, thiazide diuretics, triamterene · May decrease the renal excretion of amantadine, yielding higher and potentially toxic blood levels.
- Urinary acidifiers (e.g., methionine, ammonium chloride, ascorbic acid) · May increase the renal excretion of amantadine, potentially decreasing its efficacy.
- Trimethoprim/Sulfamethoxazole · Decreased renal clearance of amantadine, potentially leading to toxicity · moderate
- Anticholinergics · Increased anticholinergic side effects (e.g., dry mouth, urine retention) · minor
- CNS stimulants · Increased risk of agitation, restlessness, or seizures · moderate
監測
- Adverse effects (especially GI upset and agitation/behavioral changes)
- Clinical efficacy (reduction in pain scores, improved mobility)
過量
Overdoses are potentially very serious due to a fairly narrow therapeutic index. * **Cats**: Toxic dose reported is 30 mg/kg. Behavioral effects may be noted at 15 mg/kg. * **Dogs**: Behavioral effects noted at 15 mg/kg. * **Humans**: Overdoses as low as 2 grams have been fatal. Signs include cardiac dysfunction (arrhythmias, hypertension, tachycardia), pulmonary edema, CNS toxicity (tremors, seizures, psychosis, agitation, coma), hyperthermia, and renal dysfunction. **Treatment**: No specific antidote. Empty the gut if possible. Provide intensive monitoring and supportive therapy. Forced urine acidifying diuresis may increase renal excretion. Physostigmine has been suggested for cautious use in treating CNS effects.
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