Phenylephrine: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm. Last updated on Mar 23, 2020.
1. How it works
- Phenylephrine is a decongestant that constricts (shrinks) dilated blood vessels within the nose, relieving congestion.
- Injectable forms may also be used to increase blood pressure.
- It causes vasoconstriction by stimulating alpha-1 adrenergic receptors.
- Phenylephrine belongs to the class of medicines known as nasal decongestants. It may also be called a vasopressor or a selective alpha-1-adrenergic receptor agonist.
- Tablets, chewable tablets, liquid and nasal preparations of phenylephrine are used to treat nasal and sinus congestion.
- Can also relieve congestion in the eustachian tubes (the tubes that drain fluid from the inner ears).
- Phenylephrine for injection may be used in the treatment of low blood pressure, shock, or supraventricular tachycardia.
- Oral and nasal preparations of phenylephrine are available for purchase over-the-counter.
- Generic phenylephrine is available.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Sleep disturbances, restlessness, rash or itching, loss of appetite, feeling of warmth or redness under the skin.
- May not be suitable for some people including those with angina, high blood pressure, heart disease, diabetes, a thyroid disorder, spinal cord injuries, septic shock, or with circulation disorders such as peripheral vascular disease. It may also slow the heart rate or decrease how much blood the heart pumps out into the lungs. Do not use phenylephrine if you are pregnant or breastfeeding unless under a doctor's advice.
- May interact with some other medications including monoamine oxidase inhibitors and oxytocic drugs.
- Not suitable for children under four. Always talk with a doctor before giving cough or cold medicines to children.
- The injectable form of phenylephrine contains sodium metabisulfite, a sulfite that may cause allergic-type reactions in susceptible people. The injection may also cause sloughing of tissue if leakage occurs around the injection site.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Use as directed for short periods of time only. Phenylephrine only provides symptom relief, it does not cure a cold.
- Take with a full glass of water.
- Chew the chewable tablet before swallowing. Shake the oral suspension well before measuring out the correct dose. Always use a proper measuring spoon or dropper to ensure you are getting the correct dose.
- Do not give phenylephrine to children without talking to a doctor first. Phenylephrine must never be given to children under the age of four.
- Call your doctor if your symptoms have not improved within seven days of treatment, or if you develop a fast, pounding or uneven heartbeat, severe dizziness or anxiety, severe headache, fever or rash.
- Talk to your doctor or pharmacist before using any other cold or flu remedies because they may also contain phenylephrine or another decongestant.
6. Response and Effectiveness
- The decongestant effect of phenylephrine in cold or flu remedies should be noticeable within approximately 30 minutes. A rapid increase in blood pressure is usually seen following an intravenous dose that persists for up to 20 minutes.
- There is some controversy over the effectiveness of phenylephrine at dosages found in over-the-counter cold and flu remedies.
Medicines that interact with phenylephrine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with phenylephrine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with phenylephrine include:
- antidepressants, such as amitriptyline, amoxapine, clomipramine, doxepin, imipramine, isocarboxazid, or phenelzine
- diabetes medications, such as metformin, glimepiride, glipizide, glyburide, or insulin
- heart medications, such as atenolol, betaxolol, bisoprolol, carvedilol
- migraine medications, such as dihydroergotamine
Note that this list is not all-inclusive and includes only common medications that may interact with phenylephrine. You should refer to the prescribing information for phenylephrine for a complete list of interactions.
- Phenylephrine. Drugs.com. 11/2019 https://www.drugs.com/ppa/phenylephrine-systemic.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use phenylephrine only for the indication prescribed.
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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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