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Oxaprozin is a non specific prostaglandin synthesis inhibitor at the inflammatory site. It exhibits analgesic and antipyretic (anti-fever) properties for the treatment of acute and long term rheumatoid and osteoarthritis. Analgesia is provided at single doses of 1200mg, but sustained levels must be achieved for an anti-inflammatory response.
Oxaprozin is predominately metabolized in the liver via multiple pathways. Patients with renal insufficiency however, should have doses reduced since renal dysfunction affects protein binding of the drug causing reduced elimination. Its high protein binding capacity may produce drug interactions.
As with many prescription medications, Oxaprozin should be prescribed on an individual basis taking each patient’s particular medical history into account at the lowest possible effective dose. For rheumatoid patients, the normal dose is 1200mg per day, with lower doses of 600mg daily for mild to moderate osteoarthritis (degenerative joint disease, djd, OA). When indicated in cases which require a quick onset of action, an initial loading dose of 1200-1800mg, up to 26mg/kg (1kg= 2.2 pounds) may be used. Those patients weighing greater than 50kg with normal kidney and liver function, no history of peptic ulcer disease and with significant arthritis disease, may be dosed higher than 1200mg/day. The maximum daily dose nevertheless is 1800mg/day. Some patients require dividing the 1200mg doses into a twice daily regiment for better tolerance and thus compliance.
CONTRAINDICATIONS AND SIDE EFFECTS
Oxaprozin should be avoided in patients with any prior systemic sensitivity to aspirin or any of the other non-steroidal anti-inflammatory medications, patients with confirmed nasal polyps, history of allergic reactions manifest as angioedema, urticaria, or with bronchospastic or asthmatic conditions.
Adverse reactions of Oxaprozin are similar to the other non-steroidal anti-inflammatory medications and include gastrointestinal irritation with possible ulceration, perforation, bleeding, nausea, vomiting, and dyspepsia. These side effects are increased in patients with history of smoking, alcohol abuse, the elderly, and those patients with bleeding disorders. The hepatic (liver) system may be affected in 15% of the patients and manifest with elevated enzyme levels including SGOT (the most sensitive liver enzyme indicator) and SGPT (ALT), greater than three times the normal values with jaundice and hepatitis developing. Rash, fevers, and elevated components of the RBC (red blood cell system) may develop as a response to liver reactions. Effects on the kidney include interstitial nephritis, hematuria (blood in the urine) and proteinuria (protein in the urine). Renal blood flow also is reduced in certain patients with some pre-existing kidney problems due to the supportive maintenance effect of renal prostaglandins being diminished while taking the medication. This may be found in the elderly, those on long term diuretics, and patients with heart or liver disease /failure and should be closely monitored through blood test evaluation of BUN and serum creatinine. Photosensitivity reactions (skin reactions in sunlight) may occur along with rashes of varying degrees.
The protein binding capacity of Oxaprozin causes varied drug interactions. The most common being with aspirin and increased salicylate toxicity, oral coagulations and increased bleeding-though at doses of 1200mg daily no adverse reactions were noted. The H2 receptor antagonists such as Cimetidine or Ranitidine cause a reduced clearing of the non steroidal. Patients taking beta blockers may find reduced antihypertensive benefits.
Oxaprozin should be avoided during pregnancy due to its effects on the cardiovascular system as with all non steroidal medications, and premature closure of the fetal ductus arteriosus. It may be present in human milk, and so should be avoided in lactating mothers. The drug is contraindicated in pediatrics and should be prescribed in the smallest dose possible in the elderly although no dosage adjustment is required. The medication is available in 600mg caplets for oral administration.
PDR, PHYSICIANS DESK REFERENCE, edition 53 1999
MPR, PODIATRIST EDITION 2009
Personal practice experiences with Oxaprozin are limited, though I have prescribed the medication for those osteoarthritic patients or for acute joint pain of trauma who mention a difficulty in swallowing “horse pills" as the smaller caplet is less of a problem, and when a once daily dosage is desired for compliance of those patients with a busy daily routine.
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