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 (fenoprofen calcium) , the most common adverse reactions were gastrointestinal in nature and occurred in 20.8% of patients receiving Nalfon (fenoprofen calcium) as compared to 16.9% of patients receiving placebo. In descending order of frequency, these reactions included dyspepsia (10.3% Nalfon (fenoprofen calcium) , 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 (fenoprofen calcium) 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 (fenoprofen calcium) 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 (fenoprofen calcium) 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 (fenoprofen calcium) 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, SG0T, jaundice, and cholestatic hepatitis, aphthous ulcerations of the buccal mucosa, metallic taste, and pancreatitis (see PRECAUTIONS).
Hypersensitivity—Angioedema (angioneurotic edema).
Nervous System—Depression, disorientation, seizures, and trigeminal neuralgia.
Read the Nalfon (fenoprofen calcium) Side Effects Center for a complete guide to possible side effects
Reports suggest that NSAIDs may diminish the antihypertensive effect of ACE-inhibitors. This interaction should be given consideration in patients taking NSAIDs concomitantly with ACE-inhibitors.
The coadministration of aspirin decreases the biologic half-life of fenoprofen because of an increase in metabolic clearance that results in a greater amount of hydroxylated fenoprofen in the urine. Although the mechanism of interaction between fenoprofen and aspirin is not totally known, enzyme induction and displacement of fenoprofen from plasma albumin binding sites are possibilities. As with other NSAIDs, concomitant administration of fenoprofen calcium and aspirin is not generally recommended because of the potential of increased adverse effects.
Clinical studies, as well as post marketing observations, have shown that Nalfon (fenoprofen calcium) can reduce the natriuretic effect of furosemide and thiazides in some patients. This response has been attributed to inhibition of renal prostaglandin synthesis. During concomitant therapy with NSAIDs, the patient should be observed closely for signs of renal failure (see WARNINGS, Renal Effects), as well as to assure diuretic efficacy.
NSAIDs have produced an elevation of plasma lithium levels and a reduction in renal lithium clearance. The mean minimum lithium concentration increased 15% and the renal clearance was decreased by approximately 20%. These effects have been attributed to inhibition of renal prostaglandin synthesis by the NSAID. Thus, when NSAIDs and lithium are administered concurrently, subjects should be observed carefully for signs of lithium toxicity.
NSAIDs have been reported to competitively inhibit methotrexate accumulation in rabbit kidney slices. This may indicate that they could enhance the toxicity of methotrexate. Caution should be used when NSAIDs are administered concomitantly with methotrexate.
The effects of warfarin and NSAIDs on GI bleeding are synergistic, such that users of both drugs together have a risk of serious GI bleeding higher than users of either drug alone.
Chronic administration of phenobarbital, a known enzyme inducer, may be associated with a decrease in the plasma half-life of fenoprofen. When phenobarbital is added to or withdrawn from treatment, dosage adjustment of Nalfon (fenoprofen calcium) may be required.
Plasma Protein Binding
In vitro studies have shown that fenoprofen, because of its affinity for albumin, may displace from their binding sites other drugs that are also albumin bound, and this may lead to drug interactions. Theoretically, fenoprofen could likewise be displaced. Patients receiving hydantoins, sulfonamides, or sulfonylureas should be observed for increased activity of these drugs and, therefore, signs of toxicity from these drugs.
Drug/Laboratory Test Interactions
Amerlex-M kit assay values of total and free triiodothyronine in patients receiving Nalfon (fenoprofen calcium) 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.
Read the Nalfon Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 8/4/2009
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