DRUG INTERACTIONS
ACE-Inhibitors
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.
Aspirin
When ARTHROTEC is administered with aspirin, the protein binding of diclofenac is reduced, although the clearance of the free ARTHROTEC is not altered. The clinical significance of this interaction is not known; however, as with other NSAIDs, concomitant administration of diclofenac sodium and aspirin is not generally recommended because of the potential risk of increased adverse effects.
Digoxin
Elevated digoxin levels have been reported in patients receiving digoxin and diclofenac sodium. Patients receiving digoxin and ARTHROTEC should be monitored for possible digoxin toxicity.
Warfarin
The effects of warfarin and NSAIDs on GI bleeding are synergistic, such that users of both drugs together have a risk of serious bleeding greater than users of either drug alone.
Oral hypoglycemics
Diclofenac sodium does not alter glucose metabolism in healthy people nor does it alter the effects of oral hypoglycemic agents. There are rare reports, however, from marketing experience, of changes in effects of insulin or oral hypoglycemic agents in the presence of diclofenac sodium that necessitated change in the doses of such agents. Both hypo- and hyperglycemic effects have been reported. A direct causal relationship has not been established, but physicians should consider the possibility that diclofenac sodium may alter a diabetic patient's response to insulin or oral hypoglycemic agents.
Methotrexate
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.
Cyclosporine
ARTHROTEC, like other NSAID containing products, may affect renal prostaglandins and increase the toxicity of certain drugs. Ingestion of ARTHROTEC may increase cyclosporine nephrotoxicity. Patients who begin taking ARTHROTEC or who increase their dose of ARTHROTEC while taking cyclosporine may develop toxicity characteristic for clyclosporine. They should be observed closely, particularly if renal function is impaired.
Lithium
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.
Antacids
Antacids reduce the bioavailability of misoprostol acid. Antacids may also delay absorption of diclofenac sodium. Magnesium-containing antacids exacerbate misoprostol-associated diarrhea. Thus, it is not recommended that ARTHROTEC be coadministered with magnesium-containing antacids.
Diuretics
Clinical studies, as well as post marketing observations, have shown that ARTHROTEC 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. Concomitant therapy with potassium-sparing diuretics may be associated with increased serum potassium levels.
Other drugs
In small groups of patients (7–10 patients/interaction study), the concomitant administration of azathioprine, gold, chloroquine, D-penicillamine, prednisolone, doxycycline or digitoxin did not significantly affect the peak levels and AUC levels of diclofenac sodium. Phenobarbital toxicity has been reported to have occurred in a patient on chronic phenobarbital treatment following the initiation of diclofenac therapy. In vitro, diclofenac interferes minimally with the protein binding of prednisolone (10% decrease in binding). Benzylpenicillin, ampicillin, oxacillin, chlortetracycline, doxycycline, cephalothin, erythromycin, and sulfamethoxazole have no influence, in vitro, on the protein binding of diclofenac in human serum.
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