Phenylephrine
Also known as: 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
- **Hospital Use**: Injectable phenylephrine is a potent cardiovascular drug that should only be used by veterinary professionals in a clinical setting where continuous blood pressure and ECG monitoring are available. - **Oral Products**: Over-the-counter human cold medications containing phenylephrine should **never** be given to pets without explicit veterinary instruction, as they often contain other toxic ingredients (like acetaminophen or decongestants) and can cause vomiting, hyperactivity, or heart rate changes. - **Accidental Ingestion**: If your pet accidentally ingests a product containing phenylephrine, contact your veterinarian or an animal poison control center immediately.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- To increase blood pressure by vasoconstriction in pronounced systemic vasodilation or when increasing myocardial contractility is disadvantageous (e.g., hypertrophic cardiomyopathy)
- As a constant rate infusion for profound vasodilation due to septic shock
- As a vasopressor in catastrophic stages of hypovolemic shock
- As a CRI to increase peripheral vascular resistance and mean arterial blood pressure
- Diagnosis of Horner's syndrome (denervation hypersensitivity)
- General use
- As a CRI to increase peripheral vascular resistance and mean arterial blood pressure
- As a constant rate infusion for profound vasodilation due to septic shock
- As a vasopressor in catastrophic stages of hypovolemic shock
- Diagnosis of Horner's syndrome (denervation hypersensitivity)
- Hypotension secondary to drugs or vascular failure
How it is given
Possible side effects
- 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)
Cautions & contraindications
- Severe hypertension
- Ventricular tachycardia
- Hypersensitivity to phenylephrine
- Do not apply topically once ophthalmic surgery has started (to avoid direct arterial absorption)
- > **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.
Drug interactions
- Alpha-Adrenergic Blockers (phentolamine, phenothiazines, phenoxybenzamine): Higher dosages of phenylephrine may be required to attain a pressor effect if these agents have been used prior to therapy.
- Anesthetics, General (halogenated): Potentially may induce cardiac arrhythmias when used with halothane anesthesia.
- Atropine (and other anticholinergics): Block the reflex bradycardia caused by phenylephrine.
- Beta-Adrenergic Blockers: The cardiostimulatory effects of phenylephrine (seen at high doses) can be blocked.
- Digoxin: Use with phenylephrine may cause increased myocardium sensitization.
- Monoamine Oxidase (MAO) Inhibitors (e.g., amitraz, selegiline): Should not be used with phenylephrine because of a pronounced pressor effect.
- Oxytocin: When used concurrently with oxytocic agents, pressor effects may be enhanced.
- Sympathomimetic Agents (epinephrine): Tachycardia and serious arrhythmias are possible.
- Volatile anaesthetic agents: Increased risk of cardiac arrhythmias
- Oxytocic agents: Enhanced pressor effects leading to severe hypertension
Frequently asked questions
What is Phenylephrine used for in pets?
- **Hospital Use**: Injectable phenylephrine is a potent cardiovascular drug that should only be used by veterinary professionals in a clinical setting where continuous blood pressure and ECG monitoring are available. - **Oral Products**: Over-the-counter human cold medications containing phenylephrine should **never** be given to pets without explicit veterinary instruction, as they often contain other toxic ingredients (like acetaminophen or decongestants) and can cause vomiting, hyperactivity, or heart rate changes. - **Accidental Ingestion**: If your pet accidentally ingests a product containing phenylephrine, contact your veterinarian or an animal poison control center immediately.
Is Phenylephrine safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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