Oxaprozin

INDICATIONS AND USAGE Oxaprozin tablets are indicated: • For relief of the signs and symptoms of osteoarthritis • For relief of the signs and symptoms of rheumatoid arthritis • For relief of the signs and symptoms of juvenile rheumatoid arthritis Oxaprozin tablets are a non-steroidal anti-inflammatory drug indicated for: • Relief of signs and symptoms of Osteoarthritis (OA) ( 1 ) • Relief of signs and symptoms of Rheumatoid Arthritis (RA) ( 1 ) • Relief of signs and symptoms of Juvenile Rheumatoid Arthritis (JRA) ( 1 )

DOSAGE AND ADMINISTRATION Use the lowest effective dosage for shortest duration consistent with individual patient treatment goals ( 2.1) OA: 1200 mg (four 300 mg caplets) given orally once a day ( 2.2, 2.5, 14.1) RA: 1200 mg (four 300 mg caplets) given orally once a day ( 2.3, 2.5, 14.2) JRA: 600 mg (two 300 mg capsules) once daily in patients 22 to 31 kg. 900 mg (three 300 mg capsules) once daily in patients 32 to 54 kg. 1,200 mg (four 300 mg capsules) once daily in patients 55 kg or greater ( 2.4, 2.5) Use the lowest effective dosage for shortest duration consistent with individual patient treatment goals ( 2.1) OA: 1200 mg (four 300 mg caplets) given orally once a day ( 2.2, 2.5, 14.1) RA: 1200 mg (four 300 mg caplets) given orally once a day ( 2.3, 2.5, 14.2) JRA: 600 mg (two 300 mg capsules) once daily in patients 22 to 31 kg. 900 mg (three 300 mg capsules) once daily in patients 32 to 54 kg. 1,200 mg (four 300 mg capsules) once daily in patients 55 kg or greater ( 2.4, 2.5) 2.1 General Dosing Instructions Carefully consider the potential benefits and risks of OXAPROZIN CAPSULES and other treatment options before deciding to use OXAPROZIN CAPSULES. Use the lowest effective dosage for the shortest duration consistent with individual patient treatment goals [see WARNINGS AND PRECAUTIONS (5)]. Different dose strengths and formulations (e.g., capsules, tablets) of oral oxaprozin are not interchangeable. This difference should be taken into consideration when changing strengths or formulations [see Dosage and Administration (2.2, 2.3, 2.4), Cinical Pharmacology (12.3)]. The highest daily dose for OXAPROZIN CAPSULES is 1,200 mg a day. 2.2 Osteoarthritis For OA, the dosage is 1,200 mg (four 300 mg capsules) given orally once a day [see DOSAGE AND ADMINISTRATION (2.5)]. 2.3 Rheumatoid Arthritis For RA, the dosage is 1,200 mg (four 300 mg capsules) given orally once a day [see DOSAGE AND ADMINISTRATION (2.5)]. 2.4 Juvenile Rheumatoid Arthritis For JRA, in patients 6 to 16 years of age, the recommended dosage given orally once per day should be based on body weight of the patient as given in Table 1 [see DOSAGE AND ADMINISTRATION (2.5)]. Table 1. Recommended Daily Dose of OXAPROZIN CAPSULES by Body Weight in Pediatric Patients Body Weight Range (kg) Dose (mg) Number of Capsules 22 to 31 kg 600mg Two capsules 32 to 54 kg 900mg Three capsules 2 to 54 kg 1,200mg Four capsules 2.5 Individualization of Dosage After observing the response to initial therapy with OXAPROZIN CAPSULES, the dose and frequency should be adjusted to suit an individual patient's needs. In osteoarthritis and rheumatoid arthritis and juvenile rheumatoid arthritis, the dosage should be individualized to the lowest effective dose of OXAPROZIN CAPSULES to minimize adverse effects. The maximum recommended total daily dose of OXAPROZIN CAPSULES in adults and pediatric patients is 1,200 mg. Patients with low body weight should initiate therapy with 600 mg once daily. Patients with severe renal impairment or on dialysis should also initiate therapy with 600 mg once daily. If there is insufficient relief of symptoms in such patients, the dose may be cautiously increased to 1,200 mg, but only with close monitoring [see CLINICAL PHARMACOLOGY (12.3)]. Physicians should ensure that patients are tolerating lower doses without gastroenterologic, renal, hepatic, or dermatologic adverse effects before advancing to larger doses. Most patients will tolerate once-a-day dosing with OXAPROZIN CAPSULES, although divided doses may be tried in patients unable to tolerate single doses.

Cardiovascular Thrombotic Events Clinical trials of several cyclooxygenase-2 (COX-2) selective and nonselective NSAIDs of up to three years duration have shown an increased risk of serious cardiovascular (CV) thrombotic events, including myocardial infarction (MI) and stroke, which can be fatal. Based on available data, it is unclear that the risk for CV thrombotic events is similar for all NSAIDs. The relative increase in serious CV thrombotic events over baseline conferred by NSAID use appears to be similar in those with and without known CV disease or risk factors for CV disease. However, patients with known CV disease or risk factors had a higher absolute incidence of excess serious CV thrombotic events, due to their increased baseline rate. Some observational studies found that this increased risk of serious CV thrombotic events began as early as the first weeks of treatment. The increase in CV thrombotic risk has been observed most consistently at higher doses. To minimize the potential risk for an adverse CV event in NSAID-treated patients, use the lowest effective dose for the shortest duration possible. Physicians and patients should remain alert for the development of such events, throughout the entire treatment course, even in the absence of previous CV symptoms. Patients should be informed about the symptoms of serious CV events and the steps to take if they occur. There is no consistent evidence that concurrent use of aspirin mitigates the increased risk of serious CV thrombotic events associated with NSAID use. The concurrent use of aspirin and an NSAID, such as oxaprozin, increases the risk of serious gastrointestinal (GI) events [see Warnings and Precautions (5.2)]. Status Post Coronary Artery Bypass Graft (CABG) Surgery Two large, controlled clinical trials of a COX-2 selective NSAID for the treatment of pain in the first 10 to 14 days following CABG surgery found an increased incidence of myocardial infarction and stroke. NSAIDs are contraindicated in the setting of CABG [see Contraindications (4)]. Post-MI Patients Observational studies conducted in the Danish National Registry have demonstrated that patients treated with NSAIDs in the post-MI period were at increased risk of reinfarction, CV-related death, and all-cause mortality beginning in the first week of treatment. In this same cohort, the incidence of death in the first year post-MI was 20 per 100 person years in NSAID-treated patients compared to 12 per 100 person years in non-NSAID exposed patients. Although the absolute rate of death declined somewhat after the first year post-MI, the increased relative risk of death in NSAID users persisted over at least the next four years of follow-up. Avoid the use of oxaprozin in patients with a recent MI unless the benefits are expected to outweigh the risk of recurrent CV thrombotic events. If oxaprozin is used in patients with a recent MI, monitor patients for signs of cardiac ischemia. 5.2 Gastrointestinal Bleeding, Ulceration, and Perforation NSAIDs, including oxaprozin, cause serious gastrointestinal (GI) adverse events including inflammation, bleeding, ulceration, and perforation of the esophagus, stomach, small intestine, or large intestine, which can be fatal. These serious adverse events can occur at any time, with or without warning symptoms, in patients treated with NSAIDs. Only one in five patients, who develop a serious upper GI adverse event on NSAID therapy, is symptomatic. Upper GI ulcers, gross bleeding, or perforation caused by NSAIDs occurred in approximately 1% of patients treated for 3 to 6 months, and in about 2% to 4% of patients treated for one year. However, even short-term NSAID therapy is not without risk. Risk Factors for GI Bleeding, Ulceration, and Perforation Patients with a prior history of peptic ulcer disease and/or GI bleeding who used NSAIDs had a greater than 10 times increased risk for developing a GI bleed compared to patients without these risk factors. Other factors that increase the risk of GI bleeding in patients treated with NSAIDs include longer duration of NSAID therapy; concomitant use of oral corticosteroids, antiplatelet drugs (such as aspirin), anticoagulants, or selective serotonin reuptake inhibitors (SSRIs); smoking; use of alcohol; older age; and poor general health status. Most postmarketing reports of fatal GI events occurred in elderly or debilitated patients. Additionally, patients with advanced liver disease and/or coagulopathy are at increased risk for GI bleeding. Strategies to Minimize the GI Risks in NSAID-treated patients: Use the lowest effective dosage for the shortest possible duration. Avoid administration of more than one NSAID at a time. Avoid use in patients at higher risk unless benefits are expected to outweigh the increased risk of bleeding. For such patients, as well as those with active GI bleeding, consider alternate therapies other than NSAIDs. Remain alert for signs and symptoms of GI ulceration and bleeding during NSAID therapy. If a serious GI adverse event is suspected, promptly initiate evaluation and treatment, and discontinue oxaprozin until a serious GI adverse event is ruled out. In the setting of concomitant use of low-dose aspirin for cardiac prophylaxis, monitor patients more closely for evidence of GI bleeding [see Drug Interactions (7)]. 5.3 Hepatotoxicity Elevations of alanine aminotransferase (ALT) or aspartate aminotransferase (AST) (three or more times the upper limit of normal [ULN]) have been reported in approximately 1% of NSAID-treated patients in clinical trials. In addition, rare, sometimes fatal, cases of severe hepatic injury, including fulminant hepatitis, liver necrosis, and hepatic failure have been reported. Elevations of ALT or AST (less than three times ULN) may occur in up to 15% of patients treated with NSAIDs including oxaprozin. Inform patients of the warning signs and symptoms of hepatotoxicity (e.g., nausea, fatigue, lethargy, diarrhea, pruritus, jaundice, right upper quadrant tenderness, and "flu-like" symptoms). If clinical signs and symptoms consistent with liver disease develop, or if systemic manifestations occur (e.g., eosinophilia, rash), discontinue oxaprozin immediately, and perform a clinical evaluation of the patient. 5.4 Hypertension NSAIDs, including oxaprozin, can lead to new onset of hypertension or worsening of preexisting hypertension, either of which may contribute to the increased incidence of CV events. Patients taking angiotensin converting enzyme (ACE) inhibitors, thiazide diuretics, or loop diuretics may have impaired response to these therapies when taking NSAIDs [see Drug Interactions (7)]. Monitor blood pressure (BP) during the initiation of NSAID treatment and throughout the course of therapy. 5.5 Heart Failure and Edema The Coxib and traditional NSAID Trialists’ Collaboration meta-analysis of randomized controlled trials demonstrated an approximately two-fold increase in hospitalizations for heart failure in COX-2 selective-treated patients and nonselective NSAID-treated patients compared to placebo-treated patients. In a Danish National Registry study of patients with heart failure, NSAID use increased the risk of MI, hospitalization for heart failure, and death. Additionally, fluid retention and edema have been observed in some patients treated with NSAIDs. Use of oxaprozin may blunt the CV effects of several therapeutic agents used to treat these medical conditions (e.g., diuretics, ACE inhibitors, or angiotensin receptor blockers [ARBs]) [see Drug Interactions (7)]. Avoid the use of oxaprozin in patients with severe heart failure unless the benefits are expected to outweigh the risk of worsening heart failure. If oxaprozin is used in patients with severe heart failure, monitor patients for signs of worsening heart failure. 5.6 Renal Toxicity and Hyperkalemia Renal Toxicity Long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury. Renal toxicit

CONTRAINDICATIONS Oxaprozin is contraindicated in the following patients: • Known hypersensitivity (e.g., anaphylactic reactions and serious skin reactions) to oxaprozin or any components of the drug product [see Warnings and Precautions ( 5.7 , 5.9 )] • History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. Severe, sometimes fatal, anaphylactic reactions to NSAIDs have been reported in such patients [see Warnings and Precautions ( 5.7 , 5.8 )] • In the setting of CABG surgery [see Warnings and Precautions ( 5.1 )] • Known hypersensitivity to oxaprozin or any components of the drug product ( 4 ) • History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs ( 4 ) • In the setting of CABG surgery ( 4 )

DRUG INTERACTIONS See Table 2 for clinically significant drug interactions with oxaprozin [see Clinical Pharmacology ( 12.3 )] . Table 2. Clinically Significant Drug Interactions with Oxaprozin Drugs That Interfere with Hemostasis Clinical Impact • Oxaprozin and anticoagulants such as warfarin have a synergistic effect on bleeding. The concomitant use of oxaprozin and anticoagulants have an increased risk of serious bleeding compared to the use of either drug alone. • Serotonin release by platelets plays an important role in hemostasis. Case-control and cohort epidemiological studies showed that concomitant use of drugs that interfere with serotonin reuptake and an NSAID may potentiate the risk of bleeding more than an NSAID alone. Intervention Monitor patients with concomitant use of oxaprozin with anticoagulants (e.g., warfarin), antiplatelet drugs (e.g., aspirin), (SSRIs), and (SNRIs) for signs of bleeding [see Warnings and Precautions ( 5.12 )] . Aspirin Clinical Impact Controlled clinical studies showed that the concomitant use of NSAIDs and analgesic doses of aspirin does not produce any greater therapeutic effect than the use of NSAIDs alone. In a clinical study, the concomitant use of an NSAID and aspirin was associated with a significantly increased incidence of GI adverse reactions as compared to use of the NSAID alone [see Warnings and Precautions ( 5.2 )] . Intervention Concomitant use of oxaprozin and analgesic doses of aspirin is not generally recommended because of the increased risk of bleeding [see Warnings and Precautions ( 5.12 ) ]. Oxaprozin is not a substitute for low dose aspirin for cardiovascular protection. ACE Inhibitors, Angiotensin Receptor Blockers, and Beta-Blockers Clinical Impact • NSAIDs may diminish the antihypertensive effect of ACE inhibitors, ARBs, or beta-blockers (including propranolol). • In patients who are elderly, volume-depleted (including those on diuretic therapy), or have renal impairment, co-administration of an NSAID with ACE inhibitors or ARBs may result in deterioration of renal function, including possible acute renal failure. These effects are usually reversible. Intervention • During concomitant use of oxaprozin and ACE-inhibitors, ARBs, or beta-blockers, monitor blood pressure to ensure that the desired blood pressure is obtained. • During concomitant use of oxaprozin and ACE-inhibitors or ARBs in patients who are elderly, volume-depleted, or have impaired renal function, monitor for signs of worsening renal function [see Warnings and Precautions ( 5.6 )]. • When these drugs are administered concomitantly, patients should be adequately hydrated. Assess renal function at the beginning of the concomitant treatment and periodically thereafter. Diuretics Clinical Impact Clinical studies, as well as post-marketing observations, showed that NSAIDs reduced the natriuretic effect of loop diuretics (e.g., furosemide) and thiazide diuretics in some patients. This effect has been attributed to the NSAID inhibition of renal prostaglandin synthesis. Intervention During concomitant use of oxaprozin with diuretics, observe patients for signs of worsening renal function, in addition to assuring diuretic efficacy including antihypertensive effects [see Warnings and Precautions ( 5.6 )] . Digoxin Clinical Impact The concomitant use of oxaprozin with digoxin has been reported to increase the serum concentration and prolong the half-life of digoxin. Intervention During concomitant use of oxaprozin and digoxin, monitor serum digoxin levels. Lithium Clinical Impact NSAIDs have produced elevations in plasma lithium levels and reductions in renal lithium clearance . The mean minimum lithium concentration increased 15%, and the renal clearance decreased by approximately 20%. This effect has been attributed to NSAID inhibition of renal prostaglandin synthesis. Intervention During concomitant use of oxaprozin and lithium, monitor patients for signs of lithium toxicity. Methotrexate Clinical Impact Concomitant use of NSAIDs and methotrexate may increase the risk for methotrexate toxicity (e.g., neutropenia, thrombocytopenia, renal dysfunction) because NSAID administration may result in increased plasma levels of methotrexate, especially in patients receiving high doses of methotrexate. Intervention During concomitant use of oxaprozin and methotrexate, monitor patients for methotrexate toxicity. Cyclosporine Clinical Impact Concomitant use of oxaprozin and cyclosporine may increase cyclosporine's nephrotoxicity. Intervention During concomitant use of oxaprozin and cyclosporine, monitor patients for signs of worsening renal function. NSAIDs and Salicylates Clinical Impact Concomitant use of oxaprozin with other NSAIDs or salicylates (e.g., diflunisal, salsalate) increases the risk of GI toxicity, with little or no increase in efficacy [see Warnings and Precautions ( 5.2 )]. Intervention The concomitant use of oxaprozin with other NSAIDs or salicylates is not recommended. Pemetrexed Clinical Impact Concomitant use of oxaprozin and pemetrexed may increase the risk of pemetrexed-associated myelosuppression, renal, and GI toxicity (see the pemetrexed prescribing information). Intervention During concomitant use of oxaprozin and pemetrexed, in patients with renal impairment whose creatinine clearance ranges from 45 to 79 mL/min, monitor for myelosuppression, renal and GI toxicity. NSAIDs with short elimination half-lives (e.g., diclofenac, indomethacin) should be avoided for a period of two days before, the day of, and two days following administration of pemetrexed. In the absence of data regarding potential interaction between pemetrexed and NSAIDs with longer half-lives (e.g., meloxicam, nabumetone), patients taking these NSAIDs should interrupt dosing for at least five days before, the day of, and two days following pemetrexed administration. Corticosteroids Clinical Impact Concomitant use of corticosteroids with oxaprozin may increase the risk of GI ulceration or bleeding. Intervention Monitor patients with concomitant use of oxaprozin with corticosteroids for signs of bleeding [see Warnings and Precautions ( 5.2 )] . Glyburide Clinical Impact While oxaprozin does alter the pharmacokinetics of glyburide, coadministration of oxaprozin to type II non-insulin dependent diabetic patients did not affect the area under the glucose concentration curve nor the magnitude or duration of control. Intervention During concomitant use of oxaprozin and glyburide, monitor patient's blood glucose in the beginning phase of cotherapy. Laboratory Test Interactions False-positive urine immunoassay screening tests for benzodiazepines have been reported in patients taking oxaprozin. This is due to lack of specificity of the screening tests. False-positive test results may be expected for several days following discontinuation of oxaprozin therapy. Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish oxaprozin from benzodiazepines. • Drugs that Interfere with Hemostasis (e.g., warfarin, aspirin, selective serotonin reuptake inhibitors [SSRIs]/serotonin norepinephrine reuptake inhibitors [SNRIs]) : Monitor patients for bleeding who are concomitantly taking oxaprozin with drugs that interfere with hemostasis. Concomitant use of oxaprozin and analgesic doses of aspirin is not generally recommended ( 7 ) • Angiotensin Converting Enzyme (ACE) Inhibitors, Angiotensin Receptor Blockers (ARB), or Beta-Blockers : Concomitant use with oxaprozin may diminish the antihypertensive effect of these drugs. Monitor blood pressure ( 7 ) • ACE Inhibitors and ARBs : Concomitant use with oxaprozin in elderly, volume depleted, or those with renal impairment may result in deterioration of renal function. In such high risk patients, monitor for signs of worsening renal function ( 7 ) • Diuretics : NSAIDs can reduce natriuretic effect of furosemide and thiazide diuretics. Monitor patients to assure diuretic efficacy including antihypertensive

ADVERSE REACTIONS The following clinically significant adverse reactions are described elswhere in the labeling: Cardiovascular Thrombotic Events [see WARNINGS AND PRECAUTIONS (5.1)] GI Bleeding, Ulceration and Perforation [see WARNINGS AND PRECAUTIONS (5.2)] Hepatotoxicity [see WARNINGS AND PRECAUTIONS (5.3)] Hypertension [see WARNINGS AND PRECAUTIONS (5.4)] Heart Failure and Edema [see WARNINGS AND PRECAUTIONS (5.5)] Renal Toxicity and Hyperkalemia [see WARNINGS AND PRECAUTIONS (5.6)] Anaphylactic Reactions [see WARNINGS AND PRECAUTIONS (5.7)] Serious Skin Reactions [see WARNINGS AND PRECAUTIONS (5.9)] Hematologic Toxicity [see WARNINGS AND PRECAUTIONS (5.12)] Most common adverse reactions (incidence > 3%) are: constipation, diarrhea, dyspepsia, nausea, rash (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Solubiomix, LLC at 1-844-551-9911 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 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. Adverse reaction data were derived from patients who received oxaprozin, the active component of OXAPROZIN CAPSULES, in multidose, controlled, and open-label clinical trials. Rates for events from clinical trial experience are based on 2253 patients who took 1,200 mg to 1800 mg of the active component of OXAPROZIN CAPSULES per day in clinical trials. Of these, 1721 patients were treated for at least 1 month, 971 patients for at least 3 months, and 366 patients for more than 1 year. Incidence Greater than 1%: In clinical trials of oxaprozin, the active component of OXAPROZIN CAPSULES, or in patients taking other NSAIDs, the following adverse reactions occurred at an incidence greater than 1%. Cardiovascular system: edema. Digestive system: abdominal pain/distress, anorexia, constipation, diarrhea, dyspepsia, flatulence, gastrointestinal ulcers (gastric/duodenal), gross bleeding/perforation, heartburn, liver enzyme elevations, nausea, vomiting. Hematologic system: anemia, increased bleeding time. Nervous system: CNS inhibition (depression, sedation, somnolence, or confusion), disturbance of sleep, dizziness, headache. Skin and appendages: pruritus, rash. Special senses: tinnitus. Urogenital system: abnormal renal function, dysuria or frequency. Incidence Greater than 1%: The following adverse reactions were reported in clinical trials or in patients taking other NSAIDs. Body as a whole: appetite changes, death, drug hypersensitivity reactions including anaphylaxis, fever, infection, sepsis. Cardiovascular system: arrhythmia, blood pressure changes, congestive heart failure, hypertension, hypotension, myocardial infarction, palpitations, tachycardia, syncope, vasculitis. Digestive system: alteration in taste, dry mouth, eructation, esophagitis, gastritis, glossitis, hematemesis, jaundice, liver function abnormalities including liver failure, stomatitis, hemorrhoidal or rectal bleeding. Hematologic system: aplastic anemia, ecchymoses, eosinophilia, hemolytic anemia, lymphadenopathy, melena, purpura, thrombocytopenia, leukopenia. Metabolic system: hyperglycemia, weight changes. Nervous system: anxiety, asthenia, coma, convulsions, dream abnormalities, drowsiness, hallucinations, insomnia, malaise, meningitis, nervousness, paresthesia, tremors, vertigo, weakness. Respiratory system: asthma, dyspnea, pulmonary infections, pneumonia, sinusitis, symptoms of upper respiratory tract infection, respiratory depression. Skin: alopecia, angioedema, urticaria, photosensitivity, sweat. Special senses: blurred vision, conjunctivitis, hearing decrease. Urogenital: cystitis, hematuria, increase in menstrual flow, oliguria/ polyuria, proteinuria, renal insufficiency, decreased menstrual flow. Adverse Reactions in Pediatric Patients with Juvenile Rheumatoid Arthritis In a 3-month open label study in 59 pediatric patients with juvenile rheumatoid arthritis treated with oxaprozin, the active component of OXAPROZIN CAPSULES, adverse events were reported by 58% of patients. Gastrointestinal symptoms were the most frequently reported adverse effects and occurred at a higher incidence than those historically seen in controlled studies in adults. Of 30 patients who continued treatment for more than 3 months (19 to 48 weeks range total treatment duration), nine (30%) experienced rash on sun-exposed areas of the skin and five of those discontinued treatment. 6.2 Postmarketing Experience The following adverse reactions have been identified during post approval use of oxaprozin, the active component of OXAPROZIN CAPSULES. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Body as a whole: serum sickness. Digestive system: hepatitis, pancreatitis. Hematologic system: agranulocytosis, pancytopenia. Skin: pseudoporphyria, exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, fixed drug eruption (FDE), toxic epidermal necrolysis (Lyell's syndrome). Urogenital: acute interstitial nephritis, nephrotic syndrome, acute renal failure.

Mechanism of Action Oxaprozin has analgesic, anti-inflammatory, and antipyretic properties. The mechanism of action of oxaprozin, like that of other NSAIDs, is not completely understood but involves inhibition of cyclooxygenase (COX-1 and COX-2). Oxaprozin is a potent inhibitor of prostaglandin synthesis in vitro. Oxaprozin concentrations reached during therapy have produced in vivo effects. Prostaglandins sensitize afferent nerves and potentiate the action of bradykinin in inducing pain in animal models. Prostaglandins are mediators of inflammation. Because oxaprozin is an inhibitor of prostaglandin synthesis, its mode of action may be due to a decrease of prostaglandins in peripheral tissues. 12.3 Pharmacokinetics General Pharmacokinetic Characteristics In dose proportionality studies utilizing 600 mg, 1,200 mg and 1,800 mg doses, the pharmacokinetics of oxaprozin in healthy subjects demonstrated nonlinear kinetics of both the total and unbound drug in opposite directions, i.e., dose exposure related increase in the clearance of total drug and decrease in the clearance of the unbound drug. Decreased clearance of the unbound drug was related predominantly to a decrease in the volume of distribution of the unbound drug and not an increase in the elimination half-life. This phenomenon is considered to have minimal impact on drug accumulation upon multiple dosing. The pharmacokinetic parameters of oxaprozin in healthy subjects receiving a single dose or multiple once-daily doses of 1200 mg are presented in Table 3. Table 3. Oxaprozin Pharmacokinetic Parameters [Mean (%CV)] (1200 mg) Healthy Adults (19 to 78 years) Total Drug Unbound Drug Single N=35 Multiple N=12 Single N=35 Multiple N=12 Tmax (hr) 3.09 (39) 2.44 (40) 3.03 (48) 2.33 (35) Oral Clearance (L/hr/70 kg) 0.150 (24) 0.301 (29) 136 (24) 102 (45) Apparent Volume of Distribution at Steady State (Vd/F; L/70 kg) 11.7 (13) 16.7 (14) 6230 (28) 2420 (38) Elimination Half-life (hr) 54.9 (49) 41.4 (27) 27.8 (34) 19.5 (15) Tmax = time to reach the maximum plasma concentration of oxaprozin Absorption Oxaprozin is 95% absorbed after oral administration. Food may reduce the rate of absorption of oxaprozin, but the extent of absorption is unchanged. Antacids do not significantly affect the extent and rate of oxaprozin absorption. Distribution The apparent volume of distribution (Vd/F) of total oxaprozin is approximately 11 to 17 L/70 kg. Oxaprozin is 99% bound to plasma proteins, primarily to albumin. At therapeutic drug concentrations, the plasma protein binding of oxaprozin is saturable, resulting in a higher proportion of the free drug as the total drug concentration is increased. With increases in single doses or following multiple once-daily dosing, the apparent volume of distribution and clearance of total drug increased, while that of unbound drug decreased due to the effects of nonlinear protein binding. Oxaprozin penetrates into synovial tissues of rheumatoid arthritis patients with oxaprozin concentrations 2-fold and 3-fold greater than in plasma and synovial fluid, respectively. Oxaprozin is expected to be excreted in human milk based on its physical-chemical properties; however, the amount of oxaprozin excreted in breast milk has not been evaluated. Elimination Metabolism Several oxaprozin metabolites have been identified in human urine or feces. Oxaprozin is primarily metabolized in the liver, by both microsomal oxidation (65%) and glucuronic acid conjugation (35%). Ester and ether glucuronide are the major conjugated metabolites of oxaprozin. On chronic dosing, metabolites do not accumulate in the plasma of patients with normal renal function. Concentrations of the metabolites in plasma are very low. Oxaprozin’s metabolites do not have significant pharmacologic activity. The major ester and ether glucuronide conjugated metabolites have been evaluated along with oxaprozin in receptor binding studies and in vivo animal models and have demonstrated no activity. A small amount (<5%) of active phenolic metabolites are produced, but the contribution to overall activity is limited. Excretion Approximately 5% of the oxaprozin dose is excreted unchanged in the urine. Sixty-five percent (65%) of the dose is excreted in the urine and 35% in the feces as metabolites. Biliary excretion of unchanged oxaprozin is a minor pathway, and enterohepatic recycling of oxaprozin is insignificant. Upon chronic dosing, the accumulation half-life is approximately 22 hours. The elimination half-life is approximately twice the accumulation half-life due to increased binding and decreased clearance at lower concentrations. Specific Populations Geriatric: A multiple dose study comparing the pharmacokinetics of oxaprozin (1200 mg once daily) in 20 young (21 to 44 years) adults and 20 elderly (64 to 83 years) adults did not show any statistically significant differences between age groups. Pediatric: A population pharmacokinetic study indicated no clinically important age dependent changes in the apparent clearance of unbound oxaprozin between adult rheumatoid arthritis patients (N=40) and juvenile rheumatoid arthritis (JRA) patients (≥6 years, N=44) when adjustments were made for differences in body weight between these patient groups. The extent of protein binding of oxaprozin at various therapeutic total plasma concentrations was also similar between the adult and pediatric patient groups. Pharmacokinetic model-based estimates of daily exposure (AUC0-24) to unbound oxaprozin in JRA patients relative to adult rheumatoid arthritis patients suggest dose to body weight range relationships, as shown in Table 4. Table 4. Dose to Body Weight Range to Achieve Similar Steady-State Exposure (AUC0-24hr) to Unbound Oxaprozin in JRA Patients Relative to 70 kg Adult Rheumatoid Arthritis Patients Administered Oxaprozin 1200 mg Once Daily1 Dose (mg) Body Weight Range (kg) 600 22 to 31 900 32 to 54 1200 ≥ 55 1Model-based nomogram derived from unbound oxaprozin steady-state plasma concentrations in JRA patients weighing 22.1 to 42.7 kg or ≥45 kg administered oxaprozin 600 mg or 1200 mg once daily for 14 days, respectively. Race: Pharmacokinetic differences due to race have not been identified. Hepatic Impairment: Approximately 95% of oxaprozin is metabolized by the liver. However, patients with well-compensated cirrhosis do not require reduced doses of oxaprozin as compared to patients with normal hepatic function. Nevertheless, monitor patients with severe hepatic dysfunction for adverse reactions. Renal Impairment: Oxaprozin’s renal clearance decreased proportionally with creatinine clearance (CrCL), but since only approximately 5% of oxaprozin dose is excreted unchanged in the urine, the decrease in total body clearance becomes clinically important only in those subjects with highly decreased CrCL. Oxaprozin is not significantly removed from the blood in patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) due to its high protein binding. Oxaprozin plasma protein binding may decrease in patients with severe renal deficiency. Dosage adjustment may be necessary in patients with renal insufficiency [see Warnings and Precautions (5.6)]. Cardiac Failure: Well-compensated cardiac failure does not affect the plasma protein binding or the pharmacokinetics of oxaprozin. Drug Interaction Studies ACE inhibitors (enalapril): Oxaprozin has been shown to alter the pharmacokinetics of enalapril (significant decrease in dose-adjusted AUC0-24 and Cmax) and its active metabolite enalaprilat (significant increase in dose-adjusted AUC0-24) [see Drug Interactions (7)]. Aspirin: When oxaprozin was administered with aspirin, the protein binding of oxaprozin was reduced, although the clearance of free oxaprozin was not altered. The clinical significance of this interaction is not known. An in vitro study showed that oxaprozin significantly interfered with the anti-platelet activity of aspirin [see Drug Interactions (7)]. Beta-b