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Flanax/ Flanax Forte (naproxen sodium, NSAID)

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jan 29

Flanax and Flanax Forte are the brand names of naproxen sodium (naproxen Na). Flanax is available over-the-counter (OTC), so anyone can purchase it without a prescription. However, Flanax Forte is a prescription (Rx) drug due to its higher dose. Both are available as an oral tablet.


Know the basics

What is Flanax used for?

  • Mild to moderately-severe pain
  • Fever
  • Inflammation due to musculoskeletal trauma, post-operation pain, and post-dental extraction
  • Dysmenorrhea and abdominal cramping
  • Migraines

How should I take Flanax?

Flanax is available as oral tablets. The oral tablets should be taken by mouth without chewing or crushing them. The tablets should be taken with food to prevent gastric irritation.

How do I store Flanax?

This drug should be stored at room temperature (<30°C) and be protected from light and moisture. Do not store it in the refrigerator or freezer. Always check the label before using this product. For safety, keep out of the reach of children and pets.

Do not use if the printed expiration date has passed, the product seal has been broken, or the product has changed in color, odor, or consistency.

In addition, do not dispose of this product by pouring it down the drain, toilet, or into the environment. Ask your pharmacist regarding the proper way and location of disposal.

Know the precautions & warnings

What should I know before using Flanax?

NSAIDs, including naproxen, are associated with an increased risk of bleeding and gastric ulceration. This risk is further increased in older patients usually over 60 years of age, those taking blood thinners, and those with blood clotting disorders.

Some groups of people with conditions like asthma or allergic rhinitis may experience an exacerbation of symptoms after using NSAIDs.

Before using this medication, inform your doctor if you are/have:

  • Ever had an allergic reaction to Flanax or other NSAIDs
  • A history of allergy to other medications, food, or other substances
  • Taking other medications, especially other NSAIDs and blood thinners
  • Underlying health conditions

Is it safe to take Flanax during pregnancy or breastfeeding?

Naproxen is categorized as a pregnancy category B drug during the 1st and 2nd trimesters but is considered a pregnancy category D drug and is contraindicated for use during the 3rd trimester. This drug should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus, as determined by your doctor.

Naproxen may be excreted in breast milk. This drug should be used while breastfeeding only if the potential benefit justifies the potential risk to the child, as determined by your doctor.

Know the side effects

What are the side effects of Flanax?

All drugs have the potential to elicit side effects even with normal use. However, many side effects are dose-related and will resolve when it is adjusted or at the end of therapy.

Potential side effects while using this drug include:

  • Nausea
  • Diarrhea
  • Stomach upset
  • Abdominal pain
  • Indigestion
  • Headache
  • Dizziness
  • Allergic reaction
    • Rash
    • Pruritis
  • Bronchospasm
  • Blood abnormalities
    • Bleeding
    • Anemia
    • Thrombocytopenia
    • Leukopenia
    • Eosinophilia
  • Edema
  • Eye irritation
  • Photosensitivity
  • Malaise
  • Tinnitus
  • Drowsiness
    • Do not take before driving or operating machinery
  • Seek medical attention immediately if you experience any of these serious, potentially fatal drug reactions:

    • Arterial thrombotic events
      • Myocardial infarction (heart attack)
      • Stroke
    • Gastrointestinal damage
      • Peptic ulceration
      • Bleeding
    • Severe hypersensitivity reaction
      • Fever
      • Toxic epidermal necrolysis (TEN) or Stevens-Johnson Syndrome (SJS)
      • Vasculitis
      • Serum sickness
    • Hepatitis
      • Jaundice
    • Nephrotoxicity
    • Hematologic abnormalities
      • Anemia
      • Thrombocytopenia
      • Leukopenia
      • Agranulocytosis
      • Pancytopenia
    • Seizures

    You may experience some, none, or other side effects not mentioned above. If you have any concerns about a side effect or it becomes bothersome, consult your doctor or pharmacist.

    Know the interactions

    What drugs may interact with Flanax?

    This drug may interact with other medications. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and inform your doctor and pharmacist.

    Known drugs and their interactions with Naproxen include:

    • Other NSAIDs
      • GI distress
      • Ulceration
    • Salicylates
      • GI distress
    • Anticoagulants
      • Prolonged bleeding
    • Corticosteroids
      • GI bleeding
    • Hydantoins
      • Convulsions/seizures
    • Lithium
      • Decreased elimination
    • Diuretics
      • Decreased sodium excretion
    • Methotrexate
      • Increased toxicity
    • Antihypertensives
      • Decreased control of blood pressure
    • Selective serotonin reuptake inhibitors (SSRIs)
      • GI bleeding
    • Sulfonylureas
      • Increased risk of hypoglycemia
    • If you experience an adverse drug interaction, stop taking this drug and continue taking your other medication. Inform your doctor immediately to reevaluate your treatment plan. Your doctor may adjust the dose, substitute it for another drug, or direct you to stop using this drug.

      Does food or alcohol interact with naproxen?

      Naproxen is slightly less absorbed when taken with food. However, taking it with a meal prevents gastrointestinal distress. Similarly, this drug should not be taken with alcohol as it may increase the risk of gastrointestinal ulceration, bleeding, and hepatotoxicity.

      Inform your doctor or pharmacist if you have any concerns regarding food-drug interactions.

      What health conditions may interact with naproxen?

      Take this drug with caution if you have any of the following conditions or risk factors:

      • Active bronchial asthma
      • Nasal polyps
      • Rhinitis
      • Uncontrolled hypertension
      • Congestive heart failure (CHF)
      • Other cardiovascular diseases
      • Gastrointestinal diseases
      • Peptic ulcer disease (PUD)
      • Gastroesophageal reflux disease (GERD)
      • Conditions that require surgery
      • Renal or hepatic impairment
      • Women with fertility issues or are undergoing treatment
      • Inform your doctor or pharmacist if you have any concerns regarding specific health conditions.

        Understand the dosage

        The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

        What is the dose for an adult?

        For mild to moderately-severe pain, fever, inflammation

        Begin with 2 tablets for the first dose, then take 1 tablet every 8 hours.

        For postpartum pain

        Take 2 tablets as a single dose.

        For acute migraines

        Take 3 tablets at the onset of the attack. An additional 1-2 tablets may be taken after more than 30 minutes.

        The maximum daily dose for Flanax is 1375 mg, and the maximum daily dose for Flanax Forte is 550 mg twice a day.

        What is the dose for a child?

        There is no established pediatric dose. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.

        How is Flanax available?

        Flanax is available in the following dosage forms and strengths:

        • (OTC) Flanax 275 mg of naproxen
        • (Rx) Flanax Forte tablet 550 mg of naproxen (Rx-strength)

        What should I do in case of an emergency or overdose?

        In case of an emergency or an overdose, consider activated charcoal, emesis (vomiting), osmotic cathartic, or gastric lavage within 1-4 hours of ingestion. In additionally, immediately call your local emergency services or go to your nearest emergency room.

        Symptoms of overdose may include the following:

        • dizziness
        • extreme tiredness
        • drowsiness
        • stomach pain
        • heartburn
        • nausea
        • vomiting
        • slow or difficult breathing

        What should I do if I miss a dose?

        If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


        Hello Health Group does not provide medical advice, diagnosis or treatment.

        Written by

        Stephanie Nera, RPh, PharmD


        Updated Jan 29

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