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.

Severity: Major

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

Severity: Minor

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


Patients with a history of serious gastrointestinal events or alcohol abuse are at increased risk for severe gastrointestinal side effects. Fenoprofen (the active ingredient contained in Nalfon) should be used with caution in these patients.[Ref]

Gastrointestinal side effects have been reported frequently. These have included dyspepsia (up to 10%), nausea, vomiting, abdominal pain, and constipation. More serious gastrointestinal side effects include peptic ulcer with or without perforation, gastrointestinal hemorrhage, and pancreatitis.[Ref]


Hepatic side effects have included elevations in liver function tests, which may occur in up to 15% of patients. In addition, jaundice and cholestatic hepatitis have been reported.[Ref]

Elevations in liver function tests to three times normal values occur in less than 1% of patients.

Cautious use of fenoprofen with frequent monitoring of the liver function tests is recommended in patients with liver disease,[Ref]


Renal side effects have included increased serum creatinine and blood urea nitrogen, oliguria, hematuria, cystitis, interstitial nephritis, nephrotic syndrome, and renal papillary necrosis.[Ref]

Idiosyncratic nephropathy is seen more frequently with fenoprofen than with other nonsteroidal anti-inflammatory agents, and may occur days to months after initiation of therapy.

Fenoprofen may impair the ability of the kidney to cope with low renal blood flow states due to inhibition of prostaglandin-dependent afferent arteriolar vasodilation. Renal function may be further compromised in patients with heart failure, hypovolemia, cirrhosis, nephrotic syndrome, or hypoalbuminemia. Additional risk factors for nonsteroidal anti-inflammatory drug-induced renal insufficiency are advanced age and concomitant use of diuretics.

A case-control study suggested that patients who consumed 5000 or more pills containing NSAIDs during their lifetime may be at increased risk for end-stage renal disease.

Patients with reduced renal function may be at increased risk for renal side effects.[Ref]


Hypersensitivity side effects have been reported rarely. These have included eosinophilia. rash, angioedema, bronchospasm, and anaphylaxis. Fenoprofen-associated nephritis may be due to a hypersensitivity. In addition, rare cases of pulmonary hypersensitivity and severe dermatologic reactions have been reported.[Ref]


Hematological side effects have included platelet dysfunction, thrombocytopenia, agranulocytosis, pure red cell aplasia, hemolytic anemia, and aplastic anemia.[Ref]

Nervous system

Nervous system side effects have been rare. These have included dizziness, headache, nervousness, asthenia, and fatigue.[Ref]


Dermatologic side effects have included increased sweating, pruritus, and rash. In addition, rare cases of exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis have been reported.[Ref]


Lab values which may be altered by fenoprofen (the active ingredient contained in Nalfon) include elevated free and total triiodothyronine (T3) due to interference with the T3 assay.[Ref]


Nonsteroidal anti-inflammatory drugs (NSAIDs) may elevate blood pressure and antagonize the blood-pressure lowering effect of antihypertensive mediations in patients already being treated with antihypertensive drugs.[Ref]

Cardiovascular side effects have included edema and palpitations. In addition, blood pressure may be elevated by fenoprofen, which may have clinical relevance in patients with comorbid illnesses.[Ref]


1. "Product Information. Nalfon (fenoprofen)." Dista Products Company, Indianapolis, IN.

2. Ryan JR, Riley WA, Vargas R, et al "Enteric coating of fenoprofen calcium reduces gastrointestinal microbleeding." Clin Pharmacol Ther 42 (1987): 28-32

3. Singh G, Ramey DR, Morfeld D, Fries JF "Comparative toxicity of non-steroidal anti-inflammatory agents." Pharmacol Ther 62 (1994): 175-91

4. Carmichael J, Shankel SW "Effects of nonsteroidal anti-inflammatory drugs on prostaglandins and renal function." Am J Med 78 (1985): 992-1000

5. Radford RG, Holley KE, Grande JP, Larson TS, Wagoner RD, Donadio JV, Mccarthy JT "Reversible membranous nephropathy associated with the use of nonsteroidal anti-inflammatory drugs." JAMA 276 (1996): 466-9

6. Artinano M, Etheridge WB, Stroehlein KB, Barcenas CG "Progression of minimal-change glomerulopathy to focal glomerulosclerosis in a patient with fenoprofen nephropathy." Am J Nephrol 6 (1986): 353-7

7. Perneger TV, Whelton PK, Klag MJ "Risk of kidney failure associated with the use of acetaminophen, aspirin, and nonsteroidal antiinflammatory drugs." N Engl J Med 331 (1994): 1675-9

8. Curt GA, Kaldany A, Whitley LG, et al "Reversible rapidly progressive renal failure with nephrotic syndrome due to fenoprofen calcium." Ann Intern Med 92 (1980): 72-3

9. Wendland ML, Wagoner RD, Holley KE "Renal failure associated with fenoprofen." Mayo Clin Proc 55 (1980): 103-7

10. Kraus A, Alarcon-Segovia D "Low dose MTX and NSAID induced mild renal insufficiency and severe neutropenia." J Rheumatol 18 (1991): 1274

11. Stotts JS, Fang ML, Dannaker CJ, Steinman HK "Fenoprofen-induced toxic epidermal necrolysis." J Am Acad Dermatol 18 (1988): 755-7

12. Barbandi F, Quenzer F, Rapp K "Pulmonary hypersensitivity to nalfon." Ann Allergy 57 (1986): 205-7

13. Katz ME, Wang P "Fenoprofen-associated thrombocytopenia." Ann Intern Med 92 (1980): 262

14. Ashraf M, Pearson RM, Winfield DA "Aplastic anaemia associated with fenoprofen." Br Med J 284 (1982): 1301-2

15. Reitz CL, Bottomley SS "Pure red cell aplasia associated with fenoprofen." Am J Med Sci 287 (1984): 62-3

16. Gurney JR, Mills RJ "Assessment of thyroid function: complications after treatment with fenoprofen." Br Med J 292 (1986): 1560

17. Tillman J, Leask JTS, Campbell J, et al "Effect of fenoprofen on thyroid function tests." Clin Chim Acta 161 (1986): 233-8

18. Gurwitz JH, Avron J, Bohn RL, Glynn RJ, Monane M, Mogun H "Initiation of antihypertensive treatment during nonsteroidal anti-inflammatory drug therapy." JAMA 272 (1994): 781-6

19. Johnson AG, Nguyen TV, Day RO "Do nonsteroidal anti-inflammatory drugs affect blood pressure? A meta-analysis." Ann Intern Med 121 (1994): 289-300

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.