Sudafed 12 Hour (Pseudoephedrine) - Oral

What Is Sudafed 12 Hour?

Sudafed 12 Hour (pseudoephedrine) is a decongestant medication. Decongestant drugs cause the mucous membranes in nasal passages to contract, which decreases swelling and secretion of mucus. The main ingredient in Sudafed 12 Hour is called pseudoephedrine.

Pseudoephedrine works by shrinking swollen nasal passages and reducing swelling and stuffy nose (congestion). It helps open up the nasal airways and drain the sinuses.

Pseudoephedrine is typically available over-the-counter (OTC). However, depending on the state where you buy it, you may need to show your ID to purchase it. Pseudoephedrine is available under several brand names, including Sudafed 12 Hour (the extended-release formulation), Sudafed (the immediate-release formulation), and various dosage forms. It is also available generically.

Drug Facts

Generic Name: Pseudoephedrine

Brand Name(s): Sudafed, 12 Hour Cold Maximum Strength, Biofed, Cenafed, Chlor-Trimeton Nasal Decongestant, Contac 12-Hour, Dimetapp Decongestant, Efidac 24 Pseudoephedrine, ElixSure Congestion Children's, Genaphed, Pediacare Decongestant Infants, Simply Stuffy

Drug Availability: Over the counter

Administration Route: Oral

Therapeutic Classification: Decongestant

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Pseudoephedrine

Dosage Form(s): Tablet, extended-release tablet, liquid, capsule, syrup, solution

What Is Sudafed 12 Hour Used For?

Sudafed 12 Hour can relieve the symptoms of a stuffy nose. It can also help ease symptoms of sinus pain and pressure. 

A stuffy nose happens when the tissues inside become swollen from inflamed blood vessels. You may also have a runny nose and/or postnasal drip with a stuffy nose. Postnasal drip is when mucus drips down the back of your throat, causing a cough or sore throat.

A cold, flu, or sinus infection can cause a stuffy nose. Allergies, nasal polyps (growths of swollen tissue in the nose or sinuses), pregnancy, or overuse of nasal decongestant sprays (using for more than three days) can also cause congestion.

Although it helps relieve symptoms, pseudoephedrine will not necessarily treat the cause of the stuffy nose. For example, if you have a bacterial sinus infection, your healthcare provider may need to prescribe an antibiotic to treat it. If a stuffy nose is a symptom of your sinus infection, pseudoephedrine can help relieve a stuffy nose until the infection is gone.

Sudafed 12 Hour (Pseudoephedrine) Drug Information - A person with a red circle on and around their nose

Verywell / Dennis Madamba

How to Take Sudafed 12 Hour

Take Sudafed 12 Hour as directed on the label. Do not take it more often than every 12 hours, and do not take more than two doses in 24 hours.

Swallow the tablet whole with a full glass of water (8 ounces). Do not chew, crush, or cut the tablet. The tablet is designed to release over time, so it must be swallowed whole to work properly.

If Sudafed 12 Hour causes insomnia (trouble sleeping), you may want to take your last dose a few hours before bedtime. Remember to change both dosage times (morning and evening) to keep your doses 12 hours apart. For example, if you go to bed at 10 p.m., you can take Sudafed 12 Hour at 6 a.m. and 6 p.m. or 7 a.m. and 7 p.m.

Sudafed 12 Hour is different from immediate-release Sudafed, which is taken every six hours. Dosage instructions may vary based on which pseudoephedrine product you use. Make sure to read the instructions on the product's box to ensure you are taking it correctly.


Store Sudafed 12 Hour at room temperature (68 degrees to 77 degrees Fahrenheit). Keep this medication away from heat, direct light, and moisture. Also, keep securely out of the reach of children and pets.

Off-Label Uses

Healthcare providers sometimes recommend drugs for off-label use. Off-label means that the drug may be used for a purpose other than its Food and Drug Administration (FDA)-approved indication.

Pseudoephedrine is sometimes used off-label to prevent ear pain caused by pressure changes when flying on an airplane. Talk to your healthcare provider or the pharmacist at the pharmacy you are purchasing the product from before using any over-the-counter (OTC) medication for an off-label purpose.

How Long Does Pseudoephedrine Take to Work?

Immediate-release pseudoephedrine (e.g., Sudafed) typically starts to take effect after 30 minutes and reaches the maximum concentration in the blood after one to four hours. This effect can take twice as long for the extended-release formulations, such as Sudafed 12 Hour. A dose of Sudafed 12 Hour can work for up to 12 hours.

What Are the Side Effects of Sudafed 12 Hour?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Common Side Effects

The most common side effects of Sudafed 12 Hour are:

  • Trouble sleeping
  • Restlessness 
  • Nausea
  • Vomiting 
  • Weakness 
  • Headache
  • Dizziness
  • Anxiety 
  • Palpitations (feeling like your heart is racing or pounding)
  • Fast heart rate
  • High blood pressure
  • Tremor (involuntary shaking)
  • Urinary retention (having trouble urinating or emptying the bladder completely)

Severe Side Effects

Call your healthcare provider right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Fast, pounding, or irregular heartbeat
  • Dizziness 
  • Stomach pain 
  • Difficulty breathing 
  • High blood pressure
  • Severe skin reaction

Long-Term Side Effects

Sudafed 12 Hour is usually well-tolerated. Long-term side effects are rare, especially when you take it for a short time. Talk with your healthcare provider before taking the medication to ensure you are using it safely. Make sure your healthcare team knows about your medical conditions and your medications.

Severe but rare long-term side effects from pseudoephedrine can include: 

  • Anxiety
  • Bowel inflammation or other bowel problems
  • Heart attack
  • Seizures
  • High eye pressure

Acute generalized exanthematous pustulosis (AGEP) is another rare long-term side effect. AGEP is a rare skin reaction, usually caused by a drug. People with AGEP have a fever and inflamed skin with rashes and pus-filled pimples.

Report Side Effects

Pseudoephedrine may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Pseudoephedrine Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For nasal or sinus congestion:
    • For regular (short-acting) oral dosage form (capsules, oral solution, syrup, or tablets):
      • Adults and children 12 years of age and older—60 milligrams (mg) every four to six hours. Do not take more than 240 mg in twenty-four hours.
      • Children 6 to 12 years of age—30 mg every four to six hours. Do not take more than 120 mg in twenty-four hours.
      • Children 4 to 6 years of age—15 mg every four to six hours. Do not take more than 60 mg in twenty-four hours.
      • Children and infants up to 4 years of age—Use is not recommended .
    • For long-acting oral dosage form (extended-release capsules or extended-release tablets):
      • Adults and children 12 years of age and older—120 mg every 12 hours, or 240 mg every 24 hours. Do not take more than 240 mg in 24 hours.
      • Infants and children up to 12 years of age—Use is not recommended .


In some cases, you may need to modify your use of Sudafed 12 Hour. Consult a healthcare provider if you have questions about taking this medication.


Adolescents who are 12 years and older can take Sudafed 12 Hour. If the child is under 12 years old, ask a healthcare provider or pharmacist to help you choose a medicine indicated for your child’s age.

Pregnant People

There are no adequate pregnancy studies available for this medication. Check with your healthcare provider before using Sudafed 12 Hour if you are pregnant or plan to become pregnant. Sudafed 12 Hour should not be used in the first trimester (week one of pregnancy to the end of week 12). 

In the first trimester, Sudafed 12 Hour may cause harm to the fetus. For the shortest time possible, Sudafed 12 Hour may be used with caution in the second and third trimesters, only if approved by your healthcare provider.

Do not use Sudafed 12 Hour during pregnancy unless you consult a healthcare provider. Before taking Sudafed, it is better to try non-medicine measures, such as nasal saline, rest, and increased fluid intake.


Ask your healthcare provider before using Sudafed 12 Hour if you are nursing. There is little data on Sudafed 12 Hour use while breastfeeding. It is better to try non-medicine measures first.

If you use Sudafed 12 Hour, use it with caution and only if approved by your healthcare provider. Sudafed 12 Hour may reduce milk production. It is generally recommended to avoid Sudafed 12 Hour if lactation is not yet well established or you have difficulty nursing.

Older Adults

People older than 60 are more likely to have high blood pressure, heart problems, and/or decreased kidney function, and more sensitivity to the side effects of pseudoephedrine.

In this case, your healthcare provider may recommend starting at a lower dose of pseudoephedrine. However, Sudafed 12 Hour is only available in a 120 milligrams (mg) extended-release tablet that can’t be cut into lower doses.

If you are over 60, your healthcare provider may suggest taking a lower dose of immediate-release Sudafed instead of Sudafed 12 Hour based on your medical conditions. You may need to avoid Sudafed altogether. Stop taking Sudafed if you have trouble sleeping, or feel like your heart is racing or pounding.  

Kidney Problems

If you have kidney problems, you may want to be cautious about using Sudafed 12 Hour. Ask your healthcare provider before using Sudafed 12 Hour if you have kidney problems.

Missed Dose

Take Sudafed 12 Hour as needed for nasal congestion. If you miss a dose of Sudafed 12 Hour and still have symptoms, take the missed dose when you remember it. If it is almost time for the next dose, skip the missed dose and continue the regular dosing schedule. Do not double up doses.

Overdose: What Happens If I Take Too Much Sudafed 12 Hour?

Taking too much pseudoephedrine can potentially cause an overdose. Only take the recommended dosage as instructed on the medication’s packaging or consult your healthcare provider about how much you should take.

Taking more pseudoephedrine than recommended can cause:

  • Dilated pupils
  • Hallucinations
  • Hypertension
  • Heart arrhythmias
  • Seizures
  • Skin reactions

What Happens If I Overdose on Sudafed 12 Hour?

If you think you or someone else may have overdosed on Sudafed 12 Hour, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Sudafed 12 Hour, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex®

If symptoms do not improve within 7 days or if you also have a high fever, check with your doctor since these signs may mean that you have other medical problems.

What Are Reasons I Shouldn’t Take Sudafed 12 Hour?

Sudafed 12 Hour is not right for everyone.

You should not take Sudafed 12 Hour if you: 

  • Are allergic to pseudoephedrine. 
  • Took an antidepressant drug called a monoamine oxidase (MAO) inhibitor in the last two weeks
  • Are in the first trimester of pregnancy
  • Have urinary or bladder problems
  • Have glaucoma
  • Have coronary artery disease
  • Have uncontrolled or severely high blood pressure 

The following situations require that you consult your healthcare provider for advice before taking Sudafed 12 Hour:

  • High blood pressure
  • Heart disease or irregular heartbeat
  • Diabetes
  • Thyroid problems
  • Prostate problems
  • Kidney problems 
  • Phenylketonuria (PKU)
  • Children under 6 years old
  • Second or third trimester of pregnancy

What Other Medications Interact With Sudafed 12 Hour?

Before taking Sudafed 12 Hour for the first time, tell your healthcare provider about all of the medications you take. This includes prescription and OTC drugs as well as vitamins and supplements.

When taking Sudafed 12 Hour, you should not use the following medicines:

  • Bromocriptine
  • Ergot medicines like dihydroergotamine or ergotamine
  • MAO inhibitors, such as rasagiline, phenelzine, tranylcypromine, selegiline
  • Stimulant medications, such as Adderall or Ritalin

Ask your healthcare provider before using Sudafed if you use the following substances or medicines:

  • Alcohol
  • Caffeine
  • Atropine
  • Digoxin 
  • Blood pressure or heart drugs
  • Depression, mood, sleep, or anxiety medication
  • Drugs for enlarged prostate
  • Other cold, cough, or allergy medicines
  • St. John’s Wort

What Medications Are Similar?

Similar medications, including other products that contain pseudoephedrine, can be used to relieve a stuffy nose. For example, Sudafed contains an immediate-release form of pseudoephedrine (whereas Sudafed 12 Hour contains an extended-release form of pseudoephedrine). Pseudoephedrine can be found in various other cold and allergy medications, such as:

Another common OTC drug for nasal congestion is phenylephrine. Phenylephrine can be found in Sudafed PE and combination products, such as DayQuil and NyQuil.

Afrin is a nasal decongestant that is available in a nasal spray. You should only use it for three days at a time. If you use it for more than three days, it can worsen nasal congestion.

Although they do not contain pseudoephedrine, saline sprays and saline nasal rinses can also help nasal congestion. These products contain saltwater.

This list is a list of drugs also used to treat congestion. It is NOT a list of drugs recommended to take with Sudafed 12 Hour. Ask your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • What is Sudafed 12 Hour used for?

    Sudafed 12 Hour helps relieve stuffy nose or sinus pain and pressure. However, it does not treat the underlying cause of the stuffy nose.

  • How does Sudafed 12 Hour work?

    Sudafed 12 Hour works by shrinking inflamed nasal passages, which reduces swelling and congestion. This opens up the nasal airways and drains the sinuses.

  • What drugs should not be taken with Sudafed 12 Hour?

    Sudafed 12 Hour should not be combined with certain drugs. These include bromocriptine, MAO inhibitors, ergot drugs, and stimulants (Ritalin or Adderall). Check with your healthcare provider if you consume alcohol and/or caffeine, or if you take drugs for blood pressure, heart, prostate, mood, sleep, anxiety, or other cold and allergy drugs.

  • What are the side effects of Sudafed 12 Hour?

    The most common side effects of Sudafed 12 Hour are restlessness, trouble sleeping, nausea, vomiting, headache, weakness, dizziness, anxiety, heart palpitations, fast heart rate, high blood pressure, involuntary shaking, and problems urinating or emptying the bladder.

  • How do I stop taking Sudafed 12 Hour?

    You can stop taking pseudoephedrine once your symptoms resolve. If you have taken Sudafed 12 Hour for seven days and are not feeling better, talk to your healthcare provider or pharmacist.

How Can I Stay Healthy While Taking Sudafed 12 Hour?

While pseudoephedrine can help symptoms of nasal congestion, remember that it will not cure the underlying problem. If you have a bacterial infection that is causing symptoms of nasal congestion, Sudafed 12 Hour may help you feel better temporarily, but it will not cure the infection. Your healthcare provider can examine you to ensure you are taking the proper treatment.

Sudafed 12 Hour is not safe for people with certain medical conditions. Also, the cough and cold aisle at the pharmacy can be overwhelming, with many products that look alike and have similar ingredients. For these reasons, it is a good idea to ask your pharmacist to help you select a safe and appropriate product.

When taking Sudafed 12 Hour, you must swallow the tablet whole; do not chew, crush, or cut the tablet. This is because Sudafed 12 Hour is designed to release the drug into your body over a period of time. If you have difficulty swallowing the tablet, ask your pharmacist to help you select another dosage form, such as an oral liquid decongestant.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Prescribers’ Digital Reference. Pseudoephedrine hydrochloride drug summary.

  2. MedlinePlus. Stuffy or runny nose - adults.

  3. Epocrates. Sudafed Sinus Congestion 12 Hour.

  4. DailyMed. Label: Sudafed 12 Hour- pseudoephedrine hydrochloride, tablet, film coated, extended release.

  5. Glowacka K, Wiela-Hojeńska A. Pseudoephedrine-benefits and risks. Int J Mol Sci. 2021;22(10):5146. doi:10.3390/ijms22105146

  6. MedlinePlus. Pseudoephedrine.

By Karen Berger, PharmD
Karen Berger, PharmD, is a community pharmacist and medical writer/reviewer.