Phenylephrine (Sudafed Pe)
January 30, 201902,641

What is Phenylephrine?

Phenylephrine is an over-the-counter drug that relieves the symptoms of stuffy noses.1 It may be taken for colds, allergies, hay fever, and whenever the sinuses are congested. You may know it by brand names such as Sudafed Pe, Sudogest PE, Nasop, Dimetapp Cold Drops,2 Lusonal, Ah-Chew D, and PediaCare Children’s decongestant.3 While you need a doctor’s prescription for Sudafed, you won’t need a prescription for Sudafed Pe.

Drugs like phenylephrine that provide relief for blocked noses are called nasal decongestants. Nasal decongestants work by reducing swollen blood vessels in your nose.4

When the cold and flu season comes around in the winter months, nasal decongestants are usually in high demand. It is estimated that millions of Americans have congested noses every year.5 The United States Centers for Disease Control and Prevention (CDC) estimates that between 9.2 million and 35.6 million people have gotten sick from the flu since 2010.

Phenylephrine became very popular a little over ten years ago.5 In the early 2000s, the United States government moved drugs containing pseudoephedrine like Sudafed behind the counter because a lot of people were starting to use those drugs to make methamphetamines. Phenylephrine became a popular alternative for those drugs.5



Uses of Phenylephrine


Phenylephrine is used for a range of medical conditions that affect the nose, ears and eyes. Here are some medical conditions that it can be useful for improving:

  1. Phenylephrine Improves Nasal Congestion

Nasal phenylephrine is used to relieve the symptoms of nasal congestion that usually come with the common cold, hay fever, sinusitis or allergies. This is probably the most common reason why a pharmacist or doctor will prescribe phenylephrine for you.

  1. Phenylephrine Improves Ear Infections

Doctors sometimes prescribe phenylephrine to help with aches in the middle ear. If you have ever had an ear infection, your doctor may have prescribed

  1. Phenylephrine Aids Eye Surgeries

Phenylephrine also comes as an ophthalmic solution. According to a report by the United States Food and Drug Administration, eye doctors have been using this form of phenlyephrine for over 70 years to dilate the pupil before eye surgeries.7

  1. Phenylephrine Improves Eye Irritations

Phenylephrine also helps with minor eye irritations. Remember the last time you were outside and the wind blew dust particles into your eyes? That was not a lot of fun, was it? Your doctor could prescribe phenylephrine for irritations like that. Other times, your doctor or pharmacist may prescribe the drug to help with allergies like hay fever and for people whose eyes get irritated from swimming.6


Phenylephrine Mechanism of Action

Phenylephrine is called an adrenergic agonist. Simply put, phenylephrine works on your body’s receptors for adrenaline, a hormone. Adrenaline is also known as your body’s flight-or-fight hormone. It got this name because it helps your body to use all its resources to respond to emergencies in order to save your life. For example, if you were being chased by a lion, adrenaline would allow you to be able to act fast.

When a drug is an adrenergic agonist, your body thinks it is adrenaline and it is able to bind to your receptors for adrenaline and stimulate them just like adrenaline would. Adrenergic agonists like phenylephrine cause your blood vessels to constrict and increase your blood pressure.6


Phenylephrine Dosage

Adult Dosage

As with all drugs, it helps to read the instructions before using phenylephrine for that stuffy nose. Usually, one dose of about 12.2mg of phenylephrine taken four times a day should be all you need.8 Make sure you do not take more than 4 doses in a day because you could overdose.

You also want to wait for about 4 hours after taking your first dose of phenylephrine before taking another dose. This is because your body takes somewhere in the range of four hours to break down the recommended dosage.8

Child Dosage

If your child has a blocked nose, you may be tempted to relieve their symptoms with phenylephrine. After all, if it works for you it should work for them, right? However, phenylephrine may not be safe to give to your child especially if they are under 12. It is much safer to take your child to see a pharmacist or doctor. These professionals can suggest the best drug for your child if they are less than 12 years old.8


Side Effects of Phenylephrine

 More Common Side Effects

You may notice that you are suddenly finding it harder to go to bed after using phenylephrine. This could be a surprise especially if you are not typically a night owl. Insomnia is a common side effect that people experience when they use phenylephrine.

Some people also feel nervous from using phenylephrine while others feel dizzy.9 While these side effects are not typically harmful, it is still a good idea to make sure you let your doctor or pharmacist know if you start feeling unwell from taking phenylephrine, especially if you start experiencing one of the more serious side effects below.8

Serious Side Effects

Our bodies react differently to drugs and while it is less common, you may also have more serious side effects from using phenylephrine. Some people who have a harder time with phenylephrine can experience side effects that will require urgent medical help. Without serious medical help, people with these major side effects can lose their lives.

Here are some of such side effects:

  • Swelling in the face, throat, tongue and neck
  • Difficulty breathing
  • Changes in your heart rate, rhythm and blood pressure
  • Difficulty urinating in men
  • Nausea
  • Headache

If you experience these symptoms after taking phenylephrine, you should seek medical help immediately. These are most likely signs that you have an allergy to phenylephrine. Most people will not experience these symptoms, so do not worry. However, if you experience any of these symptoms or notice any severe changes in your body, make sure to contact your doctor immediately. Also stop using phenylephrine immediately unless your doctor says otherwise.


Warnings for Phenylephrine Use

 General Warnings


 Phenylephrine is not for you if you are allergic to phenylephrine hydrochloride or any of the ingredients used to make the drug. If you have any drug allergies, it is always good to tell your pharmacist so that they can keep this in mind when prescribing drugs for you.

Make sure to read the label on your favorite brand’s packaging and do not use it if you notice any ingredients you are allergic to.8 A quick glance at the contents of your favorite drug may save you, your children or other loved ones a trip to the emergency room. There are better things to do than waiting in the emergency room, aren’t there?

 Other drugs

 As other nasal decongestants can interact with the drug, you should tell your doctor or pharmacist if you are taking any other colds for your blocked nose, before using phenylephrine.8

 Also, do not use phenylephrine if you have been placed on the following drugs:

  • drugs for depression like monoamine oxidase inhibitors and amitriptyline
  • heart medicines like digoxin
  • antibiotics
  • epilepsy drugs
  • drugs to improve your blood circulation like glyceryl trinitrate and atenolol8

 Warnings for Special Groups

 Pregnant women

If you are pregnant or breast feeding, do not use phenylephrine as it can be harmful to your child’s development.8 Rather, ask your doctor for the best drug during pregnancy. We know how uncomfortable it can be to have a stuffy nose or cold but for the sake of your child’s health it is best to ask your doctor what drug to use if you have a stuffy nose and are pregnant.

Birth defects and phenylephrine

Your first trimester starts from the first day of your last period and ends on the twelfth week. At this time, you should be about three months pregnant. During this period while your baby is forming and very delicate, make sure to speak with your doctor before using medicines, even if they are over-the-counter. Using decongestants like phenylephrine in the first trimester of pregnancy has been linked to some rare birth defects in children.12

 Preexisting Medical Conditions

 Phenylephrine is not for you if you have the following medical conditions:

  1. Heart problems
  2. High blood pressure
  3. Diabetes
  4. Prostate problems
  5. Thyroid problems
  6. Glaucoma


Phenylephrine when compared to other similar drugs

 Phenylephrine vs. Claritin (Loratadine)

 Another drug that a lot of people use when their nose is congested is Loratadine. You may know this drug from its popular brand name, Claritin. Loratadine is more effective than phenylephrine when it comes to relieving the symptoms of nasal congestion due to exposure to ragweed pollen.13

Therefore, Loratadine may be a better choice if you have an allergy to pollen.

Phenylephrine vs. Guaifenesin

 Guaifenesin is a drug often taken for colds, just like phenylephrine. There is a major difference though. While phenylephrine is a nasal decongestant, Guaifenesin is an expectorant.14 Decongestants work by relieving swelling in the blood vessels of the nose. Guaifenesin works by thinning out the mucus in your air passages so you can cough it up and breathe better. Guaifenesin would be better for you if your chest feels congested while it may be a better idea to take phenylephrine if your nose is congested.

Phenylephrine vs. Pseudoephedrine

Pseudoephedrine is commonly sold as Sudafed, a prescription drug, while phenylephrine is commonly sold as Sudafed PE, a drug you can get over the counter for coughs and colds. While these two drugs are nasal decongestants, pseudoephedrine is more effective than phenylephrine.10

Both decongestants could be used for your cold. However, because pseudoephedrine is more effective for treating coughs and colds if you have been on phenylephrine for a while and you don’t feel better, you could ask your doctor for pseudoephedrine instead.

Being that both drugs are decongestants, make sure not to use them together because they can have a combined effect and this can affect your blood pressure and heart. Since phenylephrine only works for 4 hours, you may be able to take pseudoephedrine four hours after taking phenylephrine.9 Make sure to ask your doctor or pharmacist before using pseudoephedrine and phenylephrine together or after one another to be on the safe side.

 Phenylephrine vs. Oxymetazoline

 Doctors may use phenylephrine during sinus surgeries because it constricts the blood vessels.15 Another drug that constricts blood vessels is oxymetazoline. Have you ever been prescribed Afrin? If so, you were using the drug oxymetazoline. Oxymetazoline is better than phenylephrine at constricting the blood vessels because phenylephrine decreases the heart rate faster, tends to lead to more bleeding and increases the blood pressure faster. Make sure to ask your doctor before using Oxymetazoline in combination with phenylephrine, as they have similar effects on your blood vessels. They both belong to the class of drugs called vasoconstrictors.

 Phenylephrine as a Combination Drug

 Dextromethorphan and phenylephrine

Sometimes, phenylephrine is sold as a combination drug. One of these combinations is with dextromethorphan, a cough suppressant and acetaminophen, a pain reliever which also reduces fevers. Your doctor may prescribe this combination if the flu, allergies or common cold cause many symptoms like headaches, fevers, aches, coughs and congestion in your nose and sinuses.16

 Chlorpheniramine and phenylephrine

 Phenylephrine may also be combined with chlorpheniramine which is an antihistamine and helps with allergies, as well as aspirin, which helps to relieve pains and inflammation. Your doctor may combine these medicines if you have allergies, colds or the flu.2

 Phenylephrine Drug Interactions

Phenylephrine may interact with your other drugs. Ask your doctor before using phenylephrine with other drugs. Also make sure to tell your pharmacist or doctor if you are on other drugs such as:

  • Acetaminophen 17
  • Nasal sprays and other decongestants 5
  • Digoxin 5
  • Medications for diabetes 5
  • High blood pressure medications 5
  • Medicines for migraines like ergotamine, naratriptan, sumatriptan, zolmitriptan 5
  • Antidepressants like amitriptyline, clomipramine, imipramine 5
  • Beta-blockers like atenolol, carvedilol, emtroprolol, propranolol and sotalol 5
  • Calcium channel blockers like amlodipine, diltiazem, felodipine, nifedipine and verapamil.5

Abuses of Phenylephrine

If you take too much of phenylephrine, make sure to call your doctor, go to the emergency room nearest to you or call the nearest poison helpline to you.8


Phenylephrine FAQs

  • Is phenylephrine hydrochloride the same as pseudoephedrine?

No. The two drugs are similar but are not exactly the same. Both drugs can help with stuffy noses, but pseudoephedrine, which is a prescription drug, is more effective than phenylephrine hydrochloride, which you can get over the counter. Now you know why Sudafed pe, which has phenylephrine is easy to get and why you need a doctor’s prescription for Sudafed, which has pseudoephedrine.

  • How long does it take for phenylephrine to work?

Phenylephrine starts working in your body about 30 minutes after you take it. It takes about four hours to wear off.9 Due to this reason, if you want to take another drug for your cold or stuffy nose, it is best to wait about four hours.

  • Can you drink alcohol with phenylephrine?

The American College of Cardiology advises against taking alcohol when you are on phenylephrine.18 It would be a good idea to save your drink for when you get better if you are on phenylephrine. In the meantime, water or fruit juice could be a good way to down your tablet or to enjoy your meal.

  • I took phenylephrine while pregnant? What will happen if I take phenylephrine while pregnant?

It is not safe to take phenylephrine when you are pregnant. Phenylephrine has been associated with birth defects that affect the eye, ears, and limbs.12 This is especially so in the first three months of your pregnancy. It may be tempting to reach for the over-the-counter drug when you have a cold, but for the sake of your baby’s health, check with your doctor or pharmacist first.

  • Can you take phenylephrine while breastfeeding?

Phenylephrine can harm your child as it may pass into your breast milk.2 Therefore, make sure to ask your doctor the best drug to use for your cold. There may be safer alternatives you can use.

  • How long after taking phenylephrine can I take pseudoephedrine?

These two drugs are similar and so they can have a combined effect if you take them about the same time or shortly after each other. It is not a good idea to do either of those things. However, since phenylephrine lasts for four hours,9 you may be able to take pseudoephedrine about four hours after taking phenylephrine but it is best to ask your doctor first.

  • What’s the difference between Sudafed and Sudafed pe?

Sudafed PE is a brand name for phenylephrine, an over-the-counter drug commonly used for colds and stuffy noses while Sudafed is a prescription-only brand name for pseudoephedrine. While both drugs are nasal decongestants, research has found Sudafed to be more effective.10 However, you need to ask for a prescription to buy Sudafed.



  1. Phenylephrine | Michigan Medicine. Uofmhealthorg. 2017. Available at: Accessed July 14, 2017.
  2. Aspirin, chlorpheniramine, and phenylephrine | Michigan Medicine. Uofmhealthorg. 2017. Available at: Accessed July 14, 2017.
  3. Phenylephrine – National Library of Medicine – PubMed Health. PubMed Health. 2017. Available at: Accessed July 14, 2017.
  4. Decongestants – NHS Choices. Nhsuk. 2017. Available at: Accessed July 14, 2017.
  5. Pseudoephedrine: MedlinePlus Drug Information. Medlineplusgov. 2017. Available at: Accessed July 14, 2017.
  6. Phenylephrine | C9H13NO2 – PubChem. Pubchemncbinlmnihgov. 2017. Available at: Accessed July 14, 2017.
  7. UF researchers ask FDA to remove non-prescription decongestant from the market » College of Pharmacy » University of Florida. Pharmacyufledu. 2017. Available at: Accessed July 14, 2017.
  8. Phenylephrine – Medsafe. MEDSAFE: New Zealand Medicines And Medical Devices Safety Authority. 2017. Available at: Accessed July 14, 2017.
  9. Phenylephrine: MedlinePlus Drug Information. Medlineplusgov. 2017. Available at: Accessed July 14, 2017.
  10. Horak F e. A placebo-controlled study of the nasal decongestant effect of phenylephrine and pseudoephedrine in the Vienna Challenge Chamber. – PubMed – NCBI. Ncbinlmnihgov. 2017. Available at: Accessed July 14, 2017.
  11. Disease Burden of Influenza | Seasonal Influenza (Flu) | CDC. Cdcgov. 2017. Available at: Accessed July 14, 2017.
  12. Yau W, Mitchell A, Lin K, Werler M, Hernández-Díaz S. Use of Decongestants During Pregnancy and the Risk of Birth Defects. 2017.
  13. Day JH e. Efficacy of loratadine-montelukast on nasal congestion in patients with seasonal allergic rhinitis in an environmental exposure unit. – PubMed – NCBI. Ncbinlmnihgov. 2017. Available at: Accessed July 14, 2017.
  14. Guaifenesin: MedlinePlus Drug Information. Medlineplusgov. 2017. Available at: Accessed July 14, 2017.
  15. Riegle EV e. Comparison of vasoconstrictors for functional endoscopic sinus surgery in children. – PubMed – NCBI. Ncbinlmnihgov. 2017. Available at: Accessed July 14, 2017.
  16. Acetaminophen, dextromethorphan, and phenylephrine | Cigna. Cignacom. 2017. Available at: Accessed July 14, 2017.
  17. Increased Phenylephrine Plasma Levels with Administration of Acetaminophen — NEJM. New England Journal of Medicine. 2017. Available at: Accessed July 14, 2017.
  18. Phenylephrine. Cardiosmartorg. 2017. Available at: Accessed July 14, 2017.


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