The effects of anticoagulants such as 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.
NSAIDs may diminish the antihypertensive effect of angiotensin converting enzyme (ACE) inhibitors. This interaction should be given consideration in patients taking NSAIDs concomitantly with ACE-inhibitors.
Clinical studies, as well as post-marketing observations, have shown that NSAIDs can reduce the natriuretic effect of furosemide and thiazides in some patients. The 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 and Precautions (5.6)], 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, including diclofenac, and lithium are administered concurrently, patients 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, including diclofenac, are administered concomitantly with methotrexate.
Diclofenac, like other NSAIDs, may affect renal prostaglandins and increase the toxicity of certain drugs. Therefore concomitant therapy with diclofenac may increase cyclosporine’s nephrotoxicity. Caution should be used when diclofenac is administered concomitantly with cyclosporine.
Specific interaction studies of VOLTAREN® GEL and oral NSAIDs were not performed. Also, the clinical trials of VOLTAREN® GEL prohibited concomitant use of oral NSAIDS. There is systemic exposure to diclofenac following normal use of Voltaren® Gel, up to 6% of the systemic levels of a single oral dose of diclofenac sodium. [see Clinical Pharmacology (12.3)]Therefore, concomitant administration of VOLTAREN® GEL with oral NSAIDs or aspirin may result in increased adverse NSAID effects.
Concomitant use of VOLTAREN® GEL with other topical products, including topical medications, sunscreens, lotions, moisturizers, and cosmetics, on the same skin site has not been tested and should be avoided because of the potential to alter local tolerability and absorption.
The safety of VOLTAREN® GEL has not been established during pregnancy. There are no well-controlled studies of diclofenac in pregnant women. Human and animal studies indicate that diclofenac crosses the placenta. In late pregnancy, as with other NSAIDs, VOLTAREN® GEL should be avoided because it may cause premature closure of the ductus arteriosus.
Pregnancy Category C: Studies in mice, rats, and rabbits in which diclofenac was administered orally throughout gestation revealed no evidence of teratogenicity despite the induction of maternal toxicity and fetal toxicity corresponding to a human equivalent dose approximately 4.5-, 2-, and 9-fold (mouse, rat, rabbit, respectively) of the maximum human topical dose of VOLTAREN® GEL (based on bioavailability and body surface area comparison).
The use of diclofenac, as with other NSAIDs, is associated with the adverse fetal cardiovascular effect of premature closure of the ductus arteriosus.
In rat studies with oral NSAIDs, including diclofenac, as with other drugs known to inhibit prostaglandin synthesis, there is an increased incidence of dystocia and delayed parturition corresponding to a human equivalent dose approximately similar to the maximum recommended clinical dose (based on bioavailability and body surface area comparison). The effects of VOLTAREN® GEL on labor and delivery in pregnant women are unknown.
It is not known whether diclofenac is excreted in human milk; however, studies in animals detected diclofenac in the milk after oral administration. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from VOLTAREN® GEL a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness in pediatric patients have not been established.
Of the total number of subjects treated with VOLTAREN® GEL in clinical studies, 498 were 65 years of age and over. No overall differences in effectiveness or safety were observed between these subjects and younger subjects, but greater sensitivity to the effect of NSAIDs in some older individuals cannot be ruled out.
Diclofenac, as with any NSAID, is known to be substantially excreted by the kidney, and the risk of toxic reactions to VOLTAREN® GEL may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken when using VOLTAREN® GEL in the elderly, and it may be useful to monitor renal function.
There has been no experience of overdose with VOLTAREN® GEL.
No events of accidental ingestion have been reported with VOLTAREN® GEL. Effects similar to those observed after an overdose of diclofenac tablets can be expected if substantial amounts of VOLTAREN® GEL are ingested. Symptoms following acute oral NSAID overdoses are usually limited to lethargy, drowsiness, nausea, vomiting, and epigastric pain, which are generally reversible with supportive care. Gastrointestinal bleeding can occur. Hypertension, acute renal failure, respiratory depression, and coma may occur. Anaphylactoid reactions have been reported with therapeutic ingestion of NSAIDs, and may occur after an overdose.
In the event of oral ingestion resulting in significant systemic side effects, it is recommended that the stomach be emptied by vomiting or lavage. Forced diuresis may theoretically be beneficial because the drug is excreted in the urine. The effect of dialysis or hemoperfusion in the elimination of diclofenac (99% protein-bound) remains unproven. In addition to supportive measures, the use of oral activated charcoal may help to reduce the absorption of diclofenac. Supportive and symptomatic treatment should be given for complications such as renal failure, convulsions, gastrointestinal irritation, and respiratory depression. For additional information about overdose treatment, call a Poison Control Center (1-800-222-1222).
VOLTAREN® GEL (diclofenac sodium topical gel) is a nonsteroidal anti-inflammatory drug (NSAID) for topical use only. It contains the active ingredient, diclofenac sodium, in an opaque, white gel base. Diclofenac sodium is a white to slightly yellow crystalline powder. Diclofenac sodium is a benzene–acetic acid derivative. The chemical name is 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid, monosodium salt. The molecular weight is 318.14. Its molecular formula is C14 H10 Cl2 NNaO2 . It has the following structural formula:
VOLTAREN® GEL also contains carbomer homopolymer Type C, cocoyl caprylocaprate, fragrance, isopropyl alcohol, mineral oil, polyoxyl 20 cetostearyl ether, propylene glycol, purified water, and strong ammonia solution.
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