フェニレフリン
Phenylephrine
Phenylephrine Hydrochloride
別名: Neo-Synephrine · AH-chew D · Little Colds Decongestant · Lusonal · Nasop · Sudogest PE · Sudafed PE · Pedia Care Children's Decongestant · Triaminic Thin Strips Cold · Minims Phenylephrine · fenilefrina · phenylephrinum · m-synephrine · Phenylephrine hydrochloride
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| As a CRI to increase peripheral vascular resistance and mean arterial blood pressure | Low dose is 1 microgram/kg/min; high dose is 3 micrograms/kg/min | IV | CRI | — | 🌎 NA |
| As a constant rate infusion for profound vasodilation due to septic shock | 2-10 micrograms/kg/minute | IV | CRI | — | 🌎 NA |
| As a vasopressor in catastrophic stages of hypovolemic shock | 1-3 micrograms/kg/min | IV | CRI | — | 🌎 NA |
| Diagnosis of Horner's syndrome (denervation hypersensitivity) | 1% or 10% solution topically to both eyes | topical | once | single dose | 🌍 EU |
| Hypotension secondary to drugs or vascular failure | Used in conjunction with fluid therapy (exact dose not specified in monograph) | IV | CRI or as directed | Until blood pressure stabilizes | 🌍 EU |
- As a CRI to increase peripheral vascular resistance and mean arterial blood pressure: May see reflex bradycardia, and vasoconstriction can lead to excessive decreases in blood flow to liver, GI tract, and kidneys, although coronary blood flow is increased.
- Diagnosis of Horner's syndrome (denervation hypersensitivity): Time to dilation indicates lesion location: <20 mins = 3rd-order HS; 20-45 mins = 2nd-order HS; 60-90 mins = 1st-order HS or normal. 10% solution causes mydriasis in 5-8 mins in post-ganglionic lesions.
- Hypotension secondary to drugs or vascular failure: Use with caution; raises BP at the expense of vital organ perfusion.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| To increase blood pressure by vasoconstriction in pronounced systemic vasodilation or when increasing myocardial contractility is disadvantageous (e.g., hypertrophic cardiomyopathy) | 1-2 micrograms/kg/minute | IV | CRI | — | 🌎 NA |
| As a constant rate infusion for profound vasodilation due to septic shock | 2-10 micrograms/kg/minute | IV | CRI | — | 🌎 NA |
| As a vasopressor in catastrophic stages of hypovolemic shock | 1-3 micrograms/kg/min | IV | CRI | — | 🌎 NA |
| As a CRI to increase peripheral vascular resistance and mean arterial blood pressure | Low dose is 1 microgram/kg/min; high dose is 3 micrograms/kg/min | IV | CRI | — | 🌎 NA |
| Diagnosis of Horner's syndrome (denervation hypersensitivity) | 1% solution topically to both eyes | topical | once | single dose | 🌍 EU |
- To increase blood pressure by vasoconstriction in pronounced systemic vasodilation or when increasing myocardial contractility is disadvantageous (e.g., hypertrophic cardiomyopathy): Infusions of 1 microgram/kg/min significantly increased mean arterial pressure without a change in cardiac output. At 2 micrograms/kg/min, cardiac index also was increased with an increase in stroke volume index.
- As a CRI to increase peripheral vascular resistance and mean arterial blood pressure: May see reflex bradycardia, and vasoconstriction can lead to excessive decreases in blood flow to liver, GI tract, and kidneys, although coronary blood flow is increased.
- Diagnosis of Horner's syndrome (denervation hypersensitivity): Use lower concentrate solutions in cats to avoid systemic hypertension.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| General use | 5 mg | IV | Single dose | — | 🌎 NA |
- General use: ARCI UCGFS Class 3 Drug
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
フェニレフリンは、強力で直接作用型の合成交感神経模倣アミンであり、獣医学においては主にその強力な血管収縮作用のために利用されます。
主な臨床応用は以下の通りです：
- 低血圧およびショック：十分な循環血液量補充後、明らかな心刺激を引き起こすことなく血圧を上昇させるために非経口的に使用されます。
- 薬物誘発性低血圧：薬物の過剰投与や特異体質的反応（フェノチアジン系、アドレナリン遮断薬など）に続発する低血圧クリーゼに対して非常に有効です。
- 眼科用：診断用眼科検査、後虹彩癒着形成の軽減、および複雑なぶどう膜炎に伴う疼痛の緩和のために局所投与されます。
- 鼻閉改善：粘膜の充血を軽減するために点鼻投与されます。
臨床のポイント：フェニレフリンは通常用量において有意なβ-アドレナリン作用を持たないため、血圧の上昇が必要であるが心拍数や心筋仕事量の増加が禁忌である場合（例：肥大型心筋症の患者）に特に有用です。
作用機序
Phenylephrine is a highly selective alpha-1 adrenergic receptor agonist.
- Vascular Smooth Muscle: Binds to post-synaptic alpha-1 receptors → activates Gq-proteins → stimulates Phospholipase C (PLC) → cleaves PIP2 into Inositol Triphosphate (IP3) and Diacylglycerol (DAG) → IP3 triggers the release of intracellular calcium from the sarcoplasmic reticulum → profound vasoconstriction.
- Cardiovascular Effects: Intravenous administration causes peripheral vasoconstriction, leading to significant increases in both diastolic and systolic blood pressures. This sudden increase in blood pressure often triggers a baroreceptor-mediated reflex bradycardia (which can be blocked by anticholinergics like atropine).
- Organ Perfusion: Constricts most vascular beds (renal, splanchnic, pulmonary, cutaneous), though coronary blood flow is typically increased due to elevated aortic diastolic pressure.
安全性・警告
禁忌
- Severe hypertension
- Ventricular tachycardia
- Hypersensitivity to phenylephrine
- Do not apply topically once ophthalmic surgery has started (to avoid direct arterial absorption)
有害事象
- Reflex bradycardia
- CNS effects (excitement, restlessness, headache)
- Arrhythmias (rare)
- Severe extravasation injuries (tissue necrosis and sloughing)
- Hypertension
- Tachycardia
- Tissue necrosis and sloughing (if IV extravasation occurs)
注意事項
WARNING: Extravasation injuries with phenylephrine can be very serious, leading to necrosis and sloughing of surrounding tissue. IV sites must be routinely monitored. If extravasation occurs, infiltrate the ischemic area with 5-10 mg phentolamine in 10-15 mL of normal saline using a fine needle.
- Extreme Caution: Use carefully in geriatric patients, and those with hyperthyroidism, bradycardia, partial heart block, or other heart disease.
- Not a Substitute for Fluids: Phenylephrine is not a replacement for adequate volume therapy in patients with shock; hypovolemia must be corrected first.
- Pregnancy: FDA Category C. Can cause contraction of the pregnant uterus and constriction of uterine blood vessels. Use with caution.
医薬品相互作用
Higher dosages of phenylephrine may be required to attain a pressor effect if these agents have been used prior to therapy.
Potentially may induce cardiac arrhythmias when used with halothane anesthesia.
Block the reflex bradycardia caused by phenylephrine.
The cardiostimulatory effects of phenylephrine (seen at high doses) can be blocked.
Use with phenylephrine may cause increased myocardium sensitization.
Should not be used with phenylephrine because of a pronounced pressor effect.
When used concurrently with oxytocic agents, pressor effects may be enhanced.
Tachycardia and serious arrhythmias are possible.
Increased risk of cardiac arrhythmias
Enhanced pressor effects leading to severe hypertension
監視
- Cardiac rate and rhythm
- Blood gases (if possible)
- IV catheter site (for signs of extravasation)
- Blood pressure (systemic use or high-concentration topical use)
- Heart rate and rhythm (ECG)
- Pupillary response and time to dilation (for Horner's syndrome testing)
薬物動態
半減期
吸収
After oral administration, phenylephrine is rapidly metabolized in the GI tract and cardiovascular effects are generally unattainable via this route. Following IV administration, pressor effects begin almost immediately and persist for up to 20 minutes. IM onset is 10-15 minutes, lasting approximately one hour.
分布
It is unknown if phenylephrine is excreted into milk.
代謝
Metabolized by the liver.
消失
The effects of the drug are terminated by uptake into tissues.
過剰投与
The margin of safety with phenylephrine overdose is fairly wide, especially after oral administration.
Clinical Signs:
- Common findings in dogs include vomiting, lethargy, depression, hyperactivity, and tachycardia.
- Severe overdosage can cause hypertension, seizures, paresthesias, ventricular extrasystoles, and cerebral hemorrhage.
Treatment:
- Vomiting is commonly seen and may self-decontaminate oral exposures.
- Cardiovascular changes often respond well to IV fluids.
- Beta-blockers or nitroprusside may be indicated when signs (tachycardia, severe hypertension) are refractory to fluids.
製品
製剤
- Injection
- Oral tablets
- Oral solution/liquid
- Oral strips
- Ophthalmic drops
- Intranasal sprays
- Injectable: 1% (10 mg/ml) solution
- Ophthalmic: 2.5% solution (single-dose vials)
- Ophthalmic: 10% solution (single-dose vials)
動物用医薬品
- Oral combination products marketed as 'cough' syrups containing phenylephrine, pyrilamine, guaifenesin, sodium citrate, and sometimes ammonium chloride.
- Phenylephrine 1% injectable solution
- Phenylephrine 2.5% ophthalmic solution
- Phenylephrine 10% ophthalmic solution
ヒト用医薬品
- Phenylephrine HCl Oral Tablets: 10 mg (regular & chewable)
- Phenylephrine HCl Oral Solution/Liquid: 2.5 mg/mL (concentrate), 2.5 mg/5mL & 7.5 mg/5 mL
- Phenylephrine HCl Oral Strips: 2.5 mg
- Phenylephrine HCl Injection: 1% (10 mg/mL) in 1 mL & 5 mL vials and 1 mL Uni-Nest amps
- Ophthalmic and intranasal dosage forms
- Minims Phenylephrine Hydrochloride 2.5% and 10% eye drops
規制ステータス
POM (Prescription Only Medicine)
POM-V or POM depending on specific formulation.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
The injectable product should be stored protected from light. Do not use solutions if they are brown or contain a precipitate. Oxidation of the drug can occur without a color change. Commercially available ampules have air replaced with nitrogen and a sulfite added to protect against oxidation.
飼主向け情報
- 病院での使用：注射用フェニレフリンは強力な心血管系薬物であり、継続的な血圧および心電図モニタリングが可能な臨床環境において、獣医療従事者のみが使用すべきです。
- 経口製品：フェニレフリンを含む人間用の市販風邪薬は、獣医師の明確な指示がない限り、ペットには絶対に与えないでください。これらには他の有毒成分（アセトアミノフェンや充血除去薬など）が含まれていることが多く、嘔吐、多動、心拍数の異常を引き起こす可能性があります。
- 誤飲時の対応：ペットが誤ってフェニレフリンを含む製品を摂取した場合は、直ちに獣医師または動物中毒事故管理センターに連絡してください。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。