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Mechanism Of Action
DAYPRO ALTA, the potassium salt of oxaprozin, is a nonsteroidal anti-inflammatory drug (NSAID), which dissociates into the active moiety oxaprozin in vivo. Oxaprozin has analgesic, anti-inflammatory, and antipyretic properties.
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 potassium is an inhibitor of prostaglandin synthesis, its mode of action may be due to a decrease of prostaglandins in peripheral tissues.
General Pharmacokinetic Characteristics
In dose proportionality studies utilizing 600, 1200 and 1800 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. Concentration dependent changes in the protein binding also resulted in changes in the oxaprozin volume of distribution, which increased for the total drug but decreased for the unbound drug. The pharmacokinetic parameters of oxaprozin in healthy subjects receiving a single dose or multiple once-daily doses of 1200 mg are presented in Table 2.
Table 2. Oxaprozin Pharmacokinetic Parameters with DAYPRO ALTA Dosing (1200 mg) [Mean (%CV)]
|Healthy Adults (18-42 years; N=12-24)|
|Total Drug||Unbound Drug|
|Tmax (hr)||1.67 (65)||2.13 (64)||1.71 (63)||1.59 (38)|
|Oral Clearance (L/hr/70 kg)||0.125 (15)||0.289 (17)||123 (20)||86.7 (33)|
|Apparent Volume of Distribution at Steady State (Vd/F; L/70 kg)||10.14 (11)||16.24 (38)||7741 (18)||2067 (38)|
|Elimination Half-life (hr)||57.0 (15)||38.0 (29)||44.8 (23)||16.4 (11)|
|Tmax = time to reach the maximum plasma concentration of oxaprozin.|
After oral administration, DAYPRO ALTA dissociates into free oxaprozin which is 95% absorbed. Peak plasma concentration occurs at about 1 hour and 45 minutes after single dose administration (see Table 2). When DAYPRO ALTA is administered with food, the peak concentration of oxaprozin is delayed by about 45 minutes, but the extent of absorption is unchanged. Antacids do not significantly affect the extent and rate of oxaprozin absorption.
The apparent volume of distribution (Vd/F) of total oxaprozin is approximately 10-16 L/70 kg. Oxaprozin potassium 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 repetitive 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 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.
Several oxaprozin metabolites excreted in human urine or feces are considered not to have significant pharmacologic activity. Oxaprozin is primarily metabolized by the liver, by both microsomal oxidation (65%) and glucuronic acid conjugation (35%). Ester and ether glucuronides are the major conjugated metabolites of oxaprozin. A small amount (<5%) of active phenolic metabolites is produced, but the contribution to overall activity is limited.
Sixty-five percent (65%) of the dose is excreted into the urine and 35% in the feces as metabolites. Renal elimination of oxaprozin metabolites is a major pathway of elimination. Biliary excretion of unchanged oxaprozin is a minor pathway. After multiple doses of DAYPRO ALTA (1200mg QD), post-steady state mean elimination half-lives of total oxaprozin and protein unbound oxaprozin were 38.0 and 16.4 hrs, respectively (see Table 2).
Pediatric: DAYPRO ALTA has not been investigated in patients <16 years of age.
Geriatric: As with any NSAID, caution should be exercised in treating the elderly (65 years and older). No dosage adjustment is necessary in the elderly for pharmacokinetic reasons, although many elderly may need a reduced dose due to low body weight or disorders associated with aging.
Gender: No differences in pharmacokinetic parameters have been observed between male and female subjects in studies of DAYPRO ALTA.
Race: Pharmacokinetic differences due to race have not been identified in studies of DAYPRO ALTA.
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 closely for adverse reactions.
Renal Impairment: Oxaprozin’s renal clearance decreased proportionally with creatinine clearance (CrCl), but since only about 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 impairment [see WARNINGS AND PRECAUTIONS].
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 potassium 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].
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].
Beta-blockers (metoprolol): Subjects receiving 1200 mg DAYPRO once daily with 100 mg metoprolol twice daily exhibited statistically significant but transient increases in sitting and standing blood pressures after 14 days [see DRUG INTERACTIONS].
Glyburide: Oxaprozin altered the pharmacokinetics of glyburide; however, 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 [see DRUG INTERACTIONS].
H2-receptor antagonists (cimetidine, ranitidine): The total clearance of oxaprozin was reduced by 20% in subjects who concurrently received therapeutic doses of cimetidine or ranitidine; no other pharmacokinetic parameter was affected. A change of clearance of this magnitude lies within the range of normal variation and is unlikely to produce a clinically detectable difference in the outcome of therapy.
Lithium: Oxaprozin has produced an elevation in plasma lithium levels and a reduction in renal lithium clearance. The mean minimum lithium concentration increased 15%, and the renal clearance decreased by approximately 20% [see DRUG INTERACTIONS].
Methotrexate: Coadministration of oxaprozin with methotrexate resulted in approximately 36% reduction in apparent oral clearance of methotrexate [see DRUG INTERACTIONS].
Other drugs: The coadministration of oxaprozin and antacids, acetaminophen, or conjugated estrogens resulted in no statistically significant changes in pharmacokinetic parameters in single- and/or multiple-dose studies. The interaction of oxaprozin with cardiac glycosides has not been studied.
Osteoarthritis: DAYPRO ALTA 1200 mg once daily was evaluated for the relief of the signs and symptoms of osteoarthritis in a 6-month placebo-controlled study versus oxaprozin acid in over 300 patients. In this trial, treatment with DAYPRO ALTA resulted in improvement in WOMAC (Western Ontario and McMaster Universities) osteoarthritis index, a composite of pain, stiffness, and functional measures in OA. DAYPRO ALTA demonstrated significant reduction in joint pain compared to placebo and was found to be comparable to 1200 mg once daily of oxaprozin acid.
With respect to GI events, DAYPRO ALTA appeared to be less well tolerated than oxaprozin acid in this study. The rates for symptomatic ulcers (2.2%) and nausea (13%) for DAYPRO ALTA treated patients were higher than the rates observed with oxaprozin acid (0% and 6%, respectively) [see ADVERSE REACTIONS].
Rheumatoid arthritis: Oxaprozin, the active component of DAYPRO ALTA (oxaprozin potassium tablets), was evaluated for the relief of the signs and symptoms of rheumatoid arthritis in placebo and active controlled clinical trials in a total of 646 patients. Oxaprozin was given in single or divided daily doses of 600 to 1800 mg/day and was found to be comparable to 2600 to 3900 mg/day of aspirin.
Last reviewed on RxList: 6/21/2016
This monograph has been modified to include the generic and brand name in many instances.
Additional Daypro Alta Information
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