プロパンテリン臭化物
**プロパンテリン臭化物**は、合成の第四級アンモニウム抗ムスカリン（抗コリン）薬です。獣医学では主にその鎮痙作用および分泌抑制作用のために使用されます。 **主な臨床用途:** * **小動物:** 下痢、排尿筋過反射（切迫性尿失禁）、および抗コリン薬に反応する徐脈の治療。 * **馬:** 結腸の蠕動運動を抑え、直腸を弛緩させるために静脈内投与され、直腸検査や手術をより安全に行うために用いられます。 **臨床のポイント:** プロパンテリンは第四級アンモニウム化合物であるため、常にイオン化しており水溶性が高いです。この構造的特徴により、血液脳関門（BBB）を通過したり眼に浸透したりしにくくなっています。その結果、アトロピンのような第三級アミンと比較して、中枢神経系（CNS）や眼への副作用を大幅に抑えつつ、末梢の抗コリン作用（消化管の弛緩や心拍数の増加など）をもたらします。
作用機序: **Propantheline** acts as a competitive antagonist at **muscarinic acetylcholine receptors** (primarily M1, M2, and M3 subtypes) located on smooth muscle, cardiac muscle, and exocrine glands. * **Gastrointestinal Tract:** Blockade of M3 receptors → decreased smooth muscle tone and peristalsis (antispasmodic effect) + reduced gastric acid secretion. * **Urinary Tract:** Blockade of M3 receptors on the detrusor muscle → relaxation of the bladder wall → increased bladder capacity and reduced urge incontinence. * **Cardiovascular System:** Blockade of M2 receptors on the sinoatrial (SA) node → vagolytic effect → increased heart rate. * **Exocrine Glands:** Blockade of muscarinic receptors → decreased salivation and respiratory secretions.
動物種別の用量
- Detrusor hyperreflexia, urge incontinence · 0.25-0.5 mg/kg PO q12-24h · PO · q12-24h · Empirical dosage. Further studies required to substantiate beneficial effect.
- Detrusor hyperreflexia, urge incontinence · 5-7.5 mg (total dose) PO once a day to once every 3 days · PO · q24h to q72h
- Detrusor hyperreflexia, urge incontinence · 5-7.5 mg (total dose) PO q8h; 7.5 mg PO q72h · PO · q8h or q72h
- Sinus bradycardia, incomplete AV block, etc. · 0.8-1.6 mg/kg three times daily · PO · TID · Although generally ineffective, a trial may be attempted.
- Sinus bradycardia, incomplete AV block, etc. · 7.5 mg PO q8-12h · PO · q8-12h · Usually well tolerated, but improvement is usually partial and often temporary.
- Chronic colitis · 0.5 mg/kg two to three times daily · PO · BID-TID
- As an antiemetic/antidiarrheal · 0.25 mg/kg PO q8h · PO · q8h
- To reduce rectal contractions during oocyte collection · 0.04 mg/kg IV · IV · Once · Must be freshly prepared and filtered through a 0.22 micron-filter from oral tablets.
- To inhibit peristalsis for 2 hours during rectal surgery · 30 mg IV · IV · Once · Must be freshly prepared and filtered through a 0.22 micron-filter from oral tablets.
投与経路
禁忌
- Hypersensitivity to anticholinergics
- Tachycardias secondary to thyrotoxicosis or cardiac insufficiency
- Myocardial ischemia
- Unstable cardiac status during acute hemorrhage
- Gastrointestinal obstructive disease
- Paralytic ileus
- Severe ulcerative colitis
- Obstructive uropathy
- Myasthenia gravis (unless used to reverse adverse muscarinic effects secondary to therapy)
有害事象
- Dry mouth (xerostomia)
- Dry eyes (keratoconjunctivitis sicca)
- Urinary hesitancy or retention
- Tachycardia
- Constipation
- Vomiting (especially in cats)
- Hypersalivation (especially in cats)
- Ileus (at high doses, potentially leading to bacterial overgrowth)
薬物相互作用
- Antihistamines · May enhance the anticholinergic activity of propantheline.
- Benzodiazepines · May enhance the activity of propantheline.
- Cimetidine · Propantheline may decrease the absorption of cimetidine.
- Corticosteroids · Long-term concurrent use may increase intraocular pressure.
- Meperidine · May enhance the activity of propantheline.
- Nitrates · May potentiate the adverse effects of propantheline.
- Nitrofurantoin · Propantheline may enhance the actions of nitrofurantoin.
- Phenothiazines · May enhance the anticholinergic activity of propantheline.
- Sympathomimetics · Propantheline may enhance their actions.
- Ranitidine · Propantheline delays absorption but increases peak serum levels of ranitidine; relative bioavailability of ranitidine may increase by 23%.
- Thiazide Diuretics · Propantheline may enhance their actions.
モニタリング
- Clinical efficacy (resolution of diarrhea, incontinence, or bradycardia)
- Heart rate and rhythm (if indicated)
- Adverse effects (dry mouth, constipation, urinary retention)
過量投与
**Toxicity Profile:** Because of its quaternary structure, minimal CNS effects are expected following an overdose compared to tertiary amines like atropine. **Treatment:** * **Decontamination:** If recent oral ingestion, empty gut contents and administer activated charcoal and saline cathartics. * **Supportive Care:** Treat clinical signs symptomatically. Fluid therapy and standard treatments for shock may be instituted. **Do not use phenothiazines** as they may exacerbate anticholinergic effects. * **Antidote (Physostigmine):** Controversial. Reserve for extreme agitation/risk of injury, or severe/life-threatening supraventricular and sinus tachycardias. * *Human pediatric dose (reasonable for small animals):* 0.02 mg/kg slow IV; may repeat q10 minutes until reversal of toxic effects. * *Note:* Physostigmine adverse effects (bronchoconstriction, bradycardia, seizures) may be treated with small doses of IV atropine.
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。