Voltaren (Diclofenac Sodium) - Drug Interactions, Contraindications, Overdosage, etc

DRUG INTERACTIONS

Aspirin

When diclofenac is administered with aspirin, the binding of diclofenac to protein is reduced, although the clearance of free diclofenac is not altered. The clinical significance of this interaction is not known; however, as with other NSAIDs, concomitant administration of diclofenac and aspirin is not generally recommended because of the potential of increased adverse effects.

Anticoagulants

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. 

ACE-Inhibitors

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.

Diuretics

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], as well as to assure diuretic efficacy.

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, including diclofenac, and lithium are administered concurrently, patients should be observed carefully for signs of lithium toxicity.

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, including diclofenac, are administered concomitantly with methotrexate.

Cyclosporine

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.

Oral Nonsteroidal Anti-inflammatory Drugs

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] Therefore, concomitant administration of Voltaren® Gel with oral NSAIDs or aspirin may result in increased adverse NSAID effects.

Topical Treatments

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.

OVERDOSAGE

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).

CONTRAINDICATIONS

The use of Voltaren® Gel is contraindicated in patients with a known hypersensitivity to diclofenac.

Voltaren® Gel should not be administered in patients who have experienced asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. Severe, rarely fatal, anaphylactic-like reactions to NSAIDs have been reported in such patients [see Warnings and Precautions].

Voltaren® Gel is contraindicated in the setting of coronary artery bypass graft (CABG) surgery [see   Warnings and Precautions (5.1)].