プロクロルペラジン
プロクロルペラジンは強力な**フェノチアジン系制吐薬**であり、獣医療では主に犬や猫の重度の悪心および嘔吐を抑えるために使用されます。 歴史的には獣医専用の配合剤(抗コリン薬を含むDarbazine®など)として広く使用されていましたが、現在では人体用製剤を適応外使用(オフラベル)することが一般的です。 **臨床のポイント:** 広範な受容体拮抗作用を持つため、中枢性嘔吐に対して非常に有効です。しかし、顕著な鎮静作用やαアドレナリン受容体遮断(低血圧を引き起こす)のリスクがあるため、通常はマロピタントやオンダンセトロンなどの新しい標的制吐薬が無効または利用できない場合に限定して使用されます。また、軽度の鎮静作用と弱い抗コリン作用も併せ持ちます。
作用機序: Prochlorperazine exerts its antiemetic effects primarily by acting on the brain's emetic center and the **Chemoreceptor Trigger Zone (CRTZ)**. Its broad-spectrum efficacy is due to the antagonism of multiple receptor types: * **Dopaminergic (D2) Antagonism** → Blocks dopamine signaling in the CRTZ, providing the primary antiemetic effect. * **Histaminergic (H1) & Cholinergic (M1) Antagonism** → Contributes to anti-motion sickness efficacy and mild antispasmodic effects in the GI tract. * **Alpha-1 Adrenergic Antagonism** → Causes peripheral vasodilation, which is responsible for the primary adverse effect of hypotension. It also has strong extrapyramidal effects due to central dopamine blockade in the basal ganglia.
動物種別の用量
- As an antiemetic · 0.5 mg/kg · SC or IM · three times a day · Ensure adequate hydration
- As an antiemetic · 0.5 mg/kg · IM or SC · q8h
- As an antiemetic · 0.1-0.5 mg/kg · IM or SC · q6-8h
- All uses (motion sickness, emesis) · 0.1-0.5 mg/kg · IV/IM/SC · q6-8h
- All uses (motion sickness, emesis) · 0.5-1 mg/kg · PO · q8-12h
- As an antiemetic · 0.5 mg/kg · IM or SC · q8h · Ensure adequate hydration
- As an antiemetic · 0.1 mg/kg · IM · q6-8h · Use with extreme caution in dehydrated or hypotensive animals
- As an antiemetic · 0.1-0.5 mg/kg · IM or SC · q6-8h
- All uses (motion sickness, emesis) · 0.1-0.5 mg/kg · IV/IM/SC · q6-8h
- All uses (motion sickness, emesis) · 0.5-1 mg/kg · PO · q8-12h
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Hypovolemia or dehydration
- Shock
- Tetanus
- Strychnine intoxication
- Hepatic dysfunction (use with caution)
- Cardiac disease (use with caution)
有害事象
- Sedation
- Hypotension
- Muscle fasciculations and tremors (extrapyramidal signs)
- Prolactin release
- Depression
- Extrapyramidal reactions (rigidity, tremors, weakness, restlessness)
薬物相互作用
- Antacids · May cause reduced GI absorption of oral phenothiazines · moderate
- Antidiarrheal mixtures (e.g., Kaolin/pectin, bismuth subsalicylate) · May cause reduced GI absorption of oral phenothiazines
- CNS Depressant Agents (barbiturates, narcotics, anesthetics) · May cause additive CNS depression if used with phenothiazines
- Dopamine · Phenothiazines may decrease pressor effects
- Epinephrine · Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal)
- Metoclopramide · Phenothiazines may potentiate the extrapyramidal effects of metoclopramide
- Opiates · May enhance the hypotensive effects of the phenothiazines; dosages of prochlorperazine may need to be reduced
- Organophosphate Agents · Phenothiazines should not be given within one month of worming with these agents as their effects may be potentiated
- Paraquat · Toxicity of the herbicide paraquat may be increased by prochlorperazine
- Phenytoin · Metabolism may be decreased if given concurrently with phenothiazines
- Physostigmine · Toxicity may be enhanced by prochlorperazine
- Procaine · Activity may be enhanced by phenothiazines
モニタリング
- Cardiac rate, rhythm, and blood pressure (if indicated and possible to measure)
- Anti-emetic/anti-spasmodic efficacy
- Hydration and electrolyte status
- Body temperature (especially if ambient temperature is very hot or cold)
- Heart rate and rhythm
- Blood pressure
- CNS status (sedation level, extrapyramidal signs)
- Liver function (with prolonged use)
過量投与
Overdose generally presents as an exaggeration of adverse effects, particularly profound sedation, hypotension, and **extrapyramidal clinical signs** (such as torticollis, severe tremors, muscle rigidity, and excessive salivation). > **Treatment:** Acute extrapyramidal signs have been successfully treated with injectable **diphenhydramine** in humans. Hypotension should be treated with intravenous fluids; avoid epinephrine due to the risk of "epinephrine reversal" causing further vasodilation.
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。