Side Effects of Nalfon (fenoprofen)

Nalfon (fenoprofen) is a nonsteroidal anti-inflammatory drug (NSAID) used for management of mild to moderate pain, fever, and inflammation. 

Nonsteroidal anti-inflammatory drugs work by reducing the levels of prostaglandins, chemicals that are responsible for the pain, fever, and swelling of inflammation. Nalfon blocks the enzymes that make prostaglandins (cyclooxygenases), resulting in lower concentrations of prostaglandins. As a consequence, inflammation, swelling, pain and fever are reduced. 

Common side effects of Nalfon include

• rash,
• ringing in the ears,
• headaches,
• dizziness,
• drowsiness,
• abdominal pain,
• nausea,
• diarrhea,
• constipation,
• heartburn,
• fluid retention, and
• dry mouth.

Serious side effects of Nalfon include reduced ability of blood to clot and increased bleeding after an injury, stomach and intestinal bleeding and ulcers, impaired kidney function, heart attacks, high blood pressure (hypertension), and heart failure.

Drug interactions of Nalfon include lithium because Nalfon may increase the blood levels of lithium by reducing the excretion of lithium by the kidneys.

• Increased levels of lithium may lead to lithium toxicity.
• Nalfon may reduce the blood pressure lowering effects of blood pressure medications. This may occur because prostaglandins play a role in the regulation of blood pressure.
• When NSAIDs are used in combination with or aminoglycosides the blood levels of the methotrexate or aminoglycoside may increase, presumably because their elimination from the body is reduced. This may lead to more methotrexate or aminoglycoside-related side effects.
• Individuals taking oral blood thinners or anticoagulants, for example, warfarin, should avoid Nalfon because Nalfon also thins the blood, and excessive blood thinning may lead to bleeding.
• Persons who have more than three alcoholic beverages per day are at increased risk of developing stomach ulcers when taking Nalfon or other NSAIDs. 

In late pregnancy, the third trimester, as with other NSAIDs, Nalfon should be avoided because it may cause premature closure of the ductus arteriosus. 

It is unknown if Nalfon is excreted in breast milk. Consult your doctor before breastfeeding.

Common side effects include: 

• rash,
• ringing in the ears,
• headaches,
• dizziness,
• drowsiness,
• abdominal pain,
• nausea,
• diarrhea,
• constipation,
• heartburn,
• fluid retention, and
• dry mouth.

NSAIDs reduce the ability of blood to clot and therefore increase bleeding after an injury. Fenoprofen also may cause stomach and intestinal bleeding and ulcers. Sometimes, stomach ulceration and intestinal bleeding may occur without any abdominal pain. Black tarry stools, weakness, and dizziness upon standing (orthostatic hypotension) may be the only signs of the bleeding.

People who are allergic to other NSAIDs should not use fenoprofen. NSAIDs reduce the flow of blood to the kidneys and impair function of the kidneys. The impairment is most likely to occur in patients with preexisting impairment of kidney function or congestive heart failure, and use of NSAIDs in these patients should be done cautiously.

Individuals with asthma are more likely to experience allergic reactions to fenoprofen and other NSAIDs. Fluid retention, blood clots, heart attacks, high blood pressure (hypertension), and heart failure also have been associated with the use of NSAIDs.

The following adverse reactions are discussed in greater detail in other sections of the labeling:

• Cardiovascular Thrombotic Events
• GI Bleeding, Ulceration and Perforation
• Hepatotoxicity
• Hypertension
• Heart Failure and Edema
• Renal Toxicity and Hyperkalemia
• Anaphylactic Reactions
• Serious Skin Reactions
• Hematologic Toxicity

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

• During clinical studies for rheumatoid arthritis, osteoarthritis, or mild to moderate pain and studies of pharmacokinetics, complaints were compiled from a checklist of potential adverse reactions, and the following data emerged.
• These encompass observations in 6,786 patients, including 188 observed for at least 52 weeks.
• For comparison, data are also presented from complaints received from the 266 patients who received placebo in these same trials.
• During short-term studies for analgesia, the incidence of adverse reactions was markedly lower than that seen in longer-term studies.

Adverse Drug Reactions Reported In > 1% Of Patients During Clinical Trials

• Digestive System — During clinical trials with Nalfon, the most common adverse reactions were gastrointestinal in nature and occurred in 20.8% of patients receiving Nalfon as compared to 16.9% of patients receiving placebo. In descending order of frequency, these reactions included dyspepsia (10.3% Nalfon vs. 2.3% placebo), nausea (7.7% vs. 7.1%), constipation (7% vs. 1.5%), vomiting (2.6% vs. 1.9%), abdominal pain (2% vs. 1.1%), and diarrhea (1.8% vs. 4.1%). The drug was discontinued because of adverse gastrointestinal reactions in less than 2% of patients during premarketing studies.
• Nervous System — The most frequent adverse neurologic reactions were headache (8.7% vs. 7.5%) and somnolence (8.5% vs. 6.4%). Dizziness (6.5% vs. 5.6%), tremor (2.2% vs. 0.4%), and confusion (1.4% vs. none) were noted less frequently. Nalfon was discontinued in less than 0.5% of patients because of these side effects during premarketing studies.
• Skin and Appendages— Increased sweating (4.6% vs. 0.4%), pruritus (4.2% vs. 0.8%), and rash (3.7% vs. 0.4%) were reported. Nalfon was discontinued in about 1% of patients because of an adverse effect related to the skin during premarketing studies.
• Special Senses — Tinnitus (4.5% vs. 0.4%), blurred vision (2.2% vs. none), and decreased hearing (1.6% vs. none) were reported. Nalfon was discontinued in less than 0.5% of patients because of adverse effects related to the special senses during premarketing studies.
• Cardiovascular — Palpitations (2.5% vs. 0.4%). Nalfon was discontinued in about 0.5% of patients because of adverse cardiovascular reactions during premarketing studies.
• Miscellaneous — Nervousness (5.7% vs. 1.5%), asthenia (5.4% vs. 0.4%), peripheral edema (5.0% vs. 0.4%), dyspnea (2.8% vs. none), fatigue (1.7% vs. 1.5%), upper respiratory infection (1.5% vs. 5.6%), and nasopharyngitis (1.2% vs. none).

Adverse Drug Reactions Reported In < 1% Of Patients During Clinical Trials

• Digestive System—Gastritis, peptic ulcer with/without perforation, gastrointestinal hemorrhage, anorexia, flatulence, dry mouth, and blood in the stool. Increases in alkaline phosphatase, LDH, SGOT, jaundice, and cholestatic hepatitis, aphthous ulcerations of the buccal mucosa, metallic taste, and pancreatitis.
• Cardiovascular—Atrial fibrillation, pulmonary edema, electrocardiographic changes, and supraventricular tachycardia.
• Genitourinary Tract—Renal failure, dysuria, cystitis, hematuria, oliguria, azotemia, anuria, interstitial nephritis, nephrosis, and papillary necrosis.
• Hypersensitivity—Angioedema (angioneurotic edema).
• Hematologic—Purpura, bruising, hemorrhage, thrombocytopenia, hemolytic anemia, aplastic anemia, agranulocytosis, and pancytopenia.
• Nervous System—Depression, disorientation, seizures, and trigeminal neuralgia.
• Special Senses—Burning tongue, diplopia, and optic neuritis.
• Skin and Appendages—Exfoliative dermatitis, toxic epidermal necrolysis, Stevens-Johnson syndrome, and alopecia.
• Miscellaneous—Anaphylaxis, urticaria, malaise, insomnia, tachycardia, personality change, lymphadenopathy, mastodynia, and fever.

See Table 1 for clinically significant drug interactions with fenoprophen.

Table 1: Clinically Significant Drug Interactions with Fenoprofen

Drug/Laboratory Test Interactions

• Amerlex-M kit assay values of total and free triiodothyronine in patients receiving Nalfon have been reported as falsely elevated on the basis of a chemical cross-reaction that directly interferes with the assay.
• Thyroid-stimulating hormone, total thyroxine, and thyrotropin-releasing hormone response are not affected.
• Thus, results of the Amerlex-M kit assay should be interpreted with caution in these patients.