プソイドエフェドリン
プソイドエフェドリンは経口の**交感神経刺激アミン**です。獣医療では、フェニルプロパノールアミン（PPA）が使用できない場合の犬の**尿道括約筋機能不全（USMI）**に対する二次選択薬として主に利用されます。また、鼻閉改善薬や逆行性射精の治療薬としても機能します。 > **臨床のポイント:** 尿失禁の治療において、プソイドエフェドリンはPPAと比較して効果が劣り、副作用（興奮や高血圧など）を引き起こしやすいとされています。 違法なメタンフェタミン合成の前駆物質であるため、販売が厳しく制限されており、地域によっては入手が困難です。
作用機序: Pseudoephedrine acts as an **indirect-acting sympathomimetic**. * Enters sympathetic nerve terminals → stimulates the release of endogenous **norepinephrine** from storage vesicles. * Norepinephrine binds to **alpha-1 adrenergic receptors** in the smooth muscle of the urethra and blood vessels → **vasoconstriction** and **increased urethral sphincter tone** (preventing urine leakage). * Also weakly stimulates **beta-adrenergic receptors** → positive chronotropic effects (increased heart rate) and mild bronchodilation.
動物種別の用量
- As a decongestant · 1 mg/kg · PO · q8h
- For use when an antihistamine/decongestant may be useful using the pyrilamine/pseudoephedrine oral granules · ½ ounce (1 tablespoonful) per 1,000 lb body weight. May mix with feed and repeated at 12 our intervals if needed. · PO · q12h · Do not use at least 72 hours before sporting events. ARCI UCGFS CLASS 3 DRUG.
- For urinary incontinence, or as a decongestant · 0.2-0.4 mg/kg [or practically, 15-60 mg (total dose) per dog] · PO · q8-12h
- To increase urethral tone · 1.5 mg/kg · PO · two to three times a day
- For retrograde ejaculation · 4-5 mg/kg · PO · three times daily or 1 to 3 hours before semen collection or attempted breeding may be tried.
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
- Glaucoma
- Prostatic hypertrophy
- Hyperthyroidism
- Diabetes mellitus
- Cardiovascular disorders
- Hypertension
有害事象
- Panting
- Decreased appetite
- Lethargy
- Tachycardia
- CNS excitement
- Restlessness
- Insomnia
- Hypertension
- Arrhythmias
薬物相互作用
- Monoamine Oxidase (MAO) Inhibitors (e.g., amitraz, selegiline) · Should not be given within two weeks of receiving MAOIs; risk of severe hypertension and toxicity.
- Reserpine · Increased chance of hypertension if given concomitantly.
- Other Sympathomimetic Agents (e.g., ephedrine, phenylpropanolamine) · Increased toxicity may result; should not be administered together.
- Tricyclic Antidepressants (e.g., clomipramine, amitriptyline) · Increased chance of hypertension if given concomitantly.
モニタリング
- Efficacy (improvement in incontinence or congestion)
- Heart rate
- CNS stimulation (restlessness, agitation)
- Appetite
過量投与
Overdoses of pseudoephedrine can cause **hyperthermia, mydriasis, tachycardia, hypertension, vomiting, disorientation, and seizures**. * **Toxicity Thresholds:** In small animals, adverse reactions may develop at doses of 5-6 mg/kg. Deaths have occurred at doses >10-12 mg/kg. * **Clinical Signs:** Common findings in dogs include hyperactivity, tachycardia, agitation, mydriasis, restlessness, head bobbing, and panting. Cats commonly present with tachycardia. * **Treatment:** Large overdoses should be treated with gastric evacuation (if not contraindicated). Treat supportively and symptomatically (e.g., propranolol for tachycardia). Phenothiazines are preferred to treat hyperactivity, agitation, and tremors as diazepam may worsen dysphoria. Contact an animal poison control center for further guidance.
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。