Skip to Content

Nalfon Side Effects

Generic Name: fenoprofen

Note: This page contains side effects data for the generic drug fenoprofen. It is possible that some of the dosage forms included below may not apply to the brand name Nalfon.

In Summary

Common side effects of Nalfon include: headache and drowsiness. Other side effects include: palpitations, heartburn, constipation, dyspepsia, myalgia, nausea, vomiting, myasthenia, prolonged bleeding time, pruritus, nervousness, dizziness, and weakness. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to fenoprofen: oral capsule, oral tablet

As well as its needed effects, fenoprofen (the active ingredient contained in Nalfon) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking fenoprofen, check with your doctor immediately:

More common:
  • Headache
Less common:
  • Abdominal pain
  • bloating or swelling of face, arms, hands, lower legs, or feet
  • blurred vision
  • continuing ringing or buzzing or other unexplained noise in ears
  • decreased hearing
  • difficult or labored breathing
  • fast, irregular, pounding, or racing heartbeat or pulse
  • hearing loss
  • itching skin
  • rapid weight gain
  • rash
  • shortness of breath
  • tightness in chest
  • tingling of hands or feet
  • unusual weight gain or loss
  • wheezing
  • Back, leg, or stomach pains
  • black or red, tarry stools
  • bleeding gums
  • blood in vomit
  • bloody or cloudy urine
  • bloody stools
  • burning feeling in chest or stomach
  • chills
  • clay-colored stools
  • coughing up blood
  • dark urine
  • diarrhea
  • difficult, burning, or painful urination
  • difficulty in swallowing
  • dizziness
  • dry mouth
  • fever with or without chills
  • frequent urge to urinate
  • general body swelling
  • greatly decreased frequency or amount of urine
  • hoarseness
  • increased blood pressure
  • increased menstrual flow or vaginal bleeding
  • increased thirst
  • indigestion
  • large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • loss of appetite
  • lower back or side pain
  • nausea
  • nosebleeds
  • not able to pass urine
  • pale skin
  • paralysis
  • pinpoint red or purple spots on skin
  • prolonged bleeding from cuts
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red or dark brown urine
  • redness of skin
  • severe or continuing stomach pain
  • sore throat
  • sores, ulcers, or white spots on lips or in mouth
  • stomach upset
  • swelling of face, fingers, or lower legs
  • swelling of hands, legs, and feet
  • swollen or painful glands
  • tenderness in stomach area
  • troubled breathing
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • vomiting
  • vomiting of blood or material that looks like coffee grounds
  • yellow eyes or skin
Symptom of overdose
  • Dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • irregular, fast or slow, or shallow breathing
  • pale or blue lips, fingernails, or skin
  • rapid, deep breathing
  • restlessness
  • shakiness and unsteady walk
  • stomach cramps
  • unsteadiness, trembling, or other problems with muscle control or coordination

Minor Side Effects

Some fenoprofen side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common:
  • Acid or sour stomach
  • belching
  • constipation
  • heartburn
  • lack or loss of strength
  • sleepiness or unusual drowsiness
  • stomach discomfort
Less common:
  • Body aches or pain
  • cough
  • ear congestion
  • increased sweating
  • loss of voice
  • mood or mental changes
  • muscle aches
  • nasal congestion
  • sneezing
  • stuffy or runny nose
  • tremor
  • General feeling of discomfort or illness
  • sleeplessness
  • trouble sleeping
  • unable to sleep

For Healthcare Professionals

Applies to fenoprofen: compounding powder, oral capsule, oral tablet


The most frequently reported side effects were dyspepsia, headache, somnolence, nausea, dizziness, constipation, nervousness, asthenia, and peripheral edema.[Ref]


Very common (10% or more): Dyspepsia (10.3%)
Common (1% to 10%): Nausea, constipation, vomiting, abdominal pain, diarrhea
Frequency not reported: Gastritis, peptic ulcer, peptic ulcer with perforation, gastrointestinal (GI) hemorrhage, GI bleeding, flatulence, dry mouth, blood in stool, buccal mucosa aphthous ulcerations, pancreatitis, burning tongue, melena, hematemesis, ulcerative stomatitis, Crohn's disease exacerbated, colitis exacerbated[Ref]


Common (1% to 10%): Palpitations
Frequency not reported: Atrial fibrillation, electrocardiographic changed, supraventricular tachycardia, tachycardia, hypertension, cardiac failure[Ref]


Frequency not reported: Renal failure, cystitis, azotemia, interstitial nephritis, nephrosis, papillary necrosis, nephrotoxicity, nephrotic syndrome[Ref]


Frequency not reported: Dysuria, hematuria, oliguria, anuria, mastodynia, breast pain[Ref]


Frequency not reported: SGOT/AST increased, jaundice, cholestatic hepatitis, abnormal liver function[Ref]


Common (1% to 10%): Dyspnea, upper respiratory infection, nasopharyngitis
Frequency not reported: Pulmonary edema[Ref]

Nervous system

Common (1% to 10%): Headache, somnolence, dizziness, tremor
Frequency not reported: Taste metallic, seizure, trigeminal neuralgia, paresthesia, drowsiness[Ref]


Common (1% to 10%): Confusion, nervousness
Frequency not reported: Depression, disorientation, insomnia, personality changed, hallucinations[Ref]


Common (1% to 10%): Sweating increased, pruritus, rash
Frequency not reported: Angioedema, purpura, bruising, exfoliative dermatitis, toxic epidermal necrolysis, Stevens-Johnson syndrome, alopecia, urticaria, photosensitivity, sweating increased[Ref]


Frequency not reported: Hypersensitivity reaction[Ref]


Frequency not reported: Anaphylaxis[Ref]


Frequency not reported: Hemorrhage, thrombocytopenia, hemolytic anemia, aplastic anemia, agranulocytosis, pancytopenia, lymphadenopathy, neutropenia[Ref]


Common (1% to 10%): Tinnitus, decreased hearing, asthenia, peripheral edema, fatigue
Frequency not reported: Alkaline phosphatase increased, LDH increased, malaise, fever, aseptic meningitis, tinnitus, hearing decreased, vertigo, aseptic meningitis[Ref]


Common (1% to 10%): Vision blurred
Frequency not reported: Diplopia, optic neuritis, vision disturbed, optic neuritis, amblyopia, diplopia[Ref]


Frequency not reported: Anorexia[Ref]


1. "Product Information. Nalfon (fenoprofen)." Xspire Pharma, Ridgeland, MS.

2. MHRA. Medicines and Health Regulatory Agency "MHRA Drug Safety Update. Available from: URL:"

It is possible that some side effects of Nalfon may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.