Diclofenac Sodium (diclofenac sodium 50 mg) Dailymed

Revised – March 2009 Rx only Prescribing Information

Boxed Warning Section

Cardiovascular Risk

• NSAIDs may cause an increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke, which can be fatal. This risk may increase with duration of use. Patients with cardiovascular disease or risk factors for cardiovascular disease may be at greater risk (see WARNINGS).
• Diclofenac sodium delayed-release tablets are contraindicated for the treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery (see WARNINGS).

Gastrointestinal Risk

• NSAIDs cause an increased risk of serious gastrointestinal adverse events including inflammation, bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms. Elderly patients are at greater risk for serious gastrointestinal events (see WARNINGS).

Description

Diclofenac sodium is a benzeneacetic acid derivative, designated chemically as 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid, monosodium salt. The structural formula is:



Diclofenac sodium is a faintly yellowish white to light beige, virtually odorless, slightly hygroscopic crystalline powder. It is freely soluble in methanol, soluble in ethanol, sparingly soluble in water and practically insoluble in chloroform and in dilute acid. The n-octanol/water partition coefficient is 13.4 at pH 7.4 and 1545 at pH 5.2. Diclofenac sodium has a dissociation constant (pKa) of 4.0 ± 0.2 at 25°C in water.

Each enteric-coated tablet for oral administration contains 25 mg, 50 mg, or 75 mg of diclofenac sodium. In addition, each tablet contains the following inactive ingredients. Inactive ingredients: Black iron oxide, croscarmellose sodium, hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose (monohydrate), magnesium stearate, methacrylic acid copolymer, microcrystalline cellulose, polyethylene glycol, povidone, red iron oxide, and titanium dioxide. The 25 mg also contains: D&C Yellow #10 Aluminum Lake and pharmaceutical glaze shellac. The 50 mg also contains: Pharmaceutical glaze shellac and yellow iron oxide. The 75 mg also contains: carnauba wax, glycerol monostearate, shellac, and yellow iron oxide.

Clinical Pharmacology

Pharmacodynamics
Diclofenac sodium delayed-release tablets are a nonsteroidal anti-inflammatory drug (NSAID) that exhibits anti-inflammatory, analgesic, and antipyretic activities in animal models. The mechanism of action of diclofenac sodium delayed-release tablets, like that of other NSAIDs, is not completely understood but may be related to prostaglandin synthetase inhibition.
Pharmacokinetics Absorption
Diclofenac is 100% absorbed after oral administration compared to IV administration as measured by urine recovery. However, due to first-pass metabolism, only about 50% of the absorbed dose is systemically available (see Table 1). Food has no significant effect on the extent of diclofenac absorption. However, there is usually a delay in the onset of absorption of 1 to 4.5 hours and a reduction in peak plasma levels of <20%.

Table 1. Pharmacokinetic Parameters for Diclofenac

	Normal Healthy Adults (20-48 yrs.)
PK Parameter	Mean	Coefficient of Variation (%)
Absolute Bioavailability (%) [N = 7]	55	40
Tmax (hr) [N = 56]	2.3	69
Oral Clearance (CL/F; mL/min) [N = 56]	582	23
Renal Clearance (% unchanged drug in urine) [N = 7]	<1	–
Apparent Volume of Distribution (V/F; L/kg) [N = 56]	1.4	58
Terminal Half-life (hr) [N = 56]	2.3	48

Distribution
The apparent volume of distribution (V/F) of diclofenac sodium is 1.4 L/kg.

Diclofenac is more than 99% bound to human serum proteins, primarily to albumin. Serum protein binding is constant over the concentration range (0.15-105 µg/mL) achieved with recommended doses.

Diclofenac diffuses into and out of the synovial fluid. Diffusion into the joint occurs when plasma levels are higher than those in the synovial fluid, after which the process reverses and synovial fluid levels are higher than plasma levels. It is not known whether diffusion into the joint plays a role in the effectiveness of diclofenac.
Metabolism
Five diclofenac metabolites have been identified in human plasma and urine. The metabolites include 4’-hydroxy-, 5-hydroxy-, 3’-hydroxy-, 4’,5-dihydroxy- and 3’-hydroxy-4’-methoxy diclofenac. In patients with renal dysfunction, peak concentrations of metabolites 4’-hydroxy- and 5-hydroxy-diclofenac were approximately 50% and 4% of the parent compound after single oral dosing compared to 27% and 1% in normal healthy subjects. However, diclofenac metabolites undergo further glucuronidation and sulfation followed by biliary excretion.

One diclofenac metabolite 4’-hydroxy-diclofenac has very weak pharmacologic activity.
Excretion
Diclofenac is eliminated through metabolism and subsequent urinary and biliary excretion of the glucuronide and the sulfate conjugates of the metabolites. Little or no free unchanged diclofenac is excreted in the urine. Approximately 65% of the dose is excreted in the urine and approximately 35% in the bile as conjugates of unchanged diclofenac plus metabolites. Because renal elimination is not a significant pathway of elimination for unchanged diclofenac, dosing adjustment in patients with mild to moderate renal dysfunction is not necessary. The terminal half-life of unchanged diclofenac is approximately 2 hours.
Special Populations Pediatric
The pharmacokinetics of diclofenac sodium delayed-release tablets has not been investigated in pediatric patients.
Race
Pharmacokinetics differences due to race have not been identified.
Hepatic Insufficiency
Hepatic metabolism accounts for almost 100% of diclofenac sodium delayed-release tablets elimination, so patients with hepatic disease may require reduced doses of diclofenac sodium delayed-release tablets compared to patients with normal hepatic function.
Renal Insufficiency
Diclofenac pharmacokinetics has been investigated in subjects with renal insufficiency. No differences in the pharmacokinetics of diclofenac have been detected in studies of patients with renal impairment. In patients with renal impairment (inulin clearance 60-90, 30-60, and <30 mL/min; N=6 in each group), AUC values and elimination rate were comparable to those in healthy subjects.

Indications And Usage

Carefully consider the potential benefits and risks of diclofenac sodium delayed-release tablets and other treatment options before deciding to use diclofenac sodium delayed-release tablets. Use the lowest effective dose for the shortest duration consistent with individual patient treatment goals (see WARNINGS ).

Diclofenac sodium delayed-release tablets, are indicated:

• For relief of signs and symptoms of osteoarthritis
• For relief of signs and symptoms of rheumatoid arthritis
• For acute or long-term use in the relief of signs and symptoms of ankylosing spondylitis

Contraindications

Diclofenac sodium delayed-release tablets, are contraindicated in patients with known hypersensitivity to diclofenac.

Diclofenac sodium delayed-release tablets should not be given to 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: Anaphylactoid Reactions and PRECAUTIONS: Preexisting Asthma ).

Diclofenac sodium delayed-release tablets are contraindicated for the treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery (see WARNINGS ).

Warnings

CARDIOVASCULAR EFFECTS Cardiovascular Thrombotic Events
Clinical trials of several COX-2 selective and nonselective NSAIDs of up to three years duration have shown an increased risk of serious cardiovascular (CV) thrombotic events, myocardial infarction, and stroke, which can be fatal. All NSAIDs, both COX-2 selective and nonselective, may have a similar risk. Patients with known CV disease or risk factors for CV disease may be at greater risk. To minimize the potential risk for an adverse CV event in patients treated with an NSAID, the lowest effective dose should be used for the shortest duration possible. Physicians and patients should remain alert for the development of such events, even in the absence of previous CV symptoms. Patients should be informed about the signs and/or symptoms of serious CV events and the steps to take if they occur.

There is no consistent evidence that concurrent use of aspirin mitigates the increased risk of serious CV thrombotic events associated with NSAID use. The concurrent use of aspirin and an NSAID does increase the risk of serious GI events (see WARNINGS: Gastrointestinal (GI) Effects ).

Two large, controlled, clinical trials of a COX-2 selective NSAID for the treatment of pain in the first 10-14 days following CABG surgery found an increased incidence of myocardial infarction and stroke (see CONTRAINDICATIONS ).
Hypertension
NSAIDs can lead to onset of new hypertension or worsening of pre-existing hypertension, either of which may contribute to the increased incidence of CV events. Patients taking thiazides or loop diuretics may have impaired response to these therapies when taking NSAIDs. NSAIDs, including diclofenac sodium delayed-release tablets, should be used with caution in patients with hypertension. Blood pressure (BP) should be monitored closely during the initiation of NSAID treatment and throughout the course of therapy.
Congestive Heart Failure and Edema Renal Effects
Fluid retention and edema have been observed in some patients taking NSAIDs. Diclofenac sodium delayed-release tablets should be used with caution in patients with fluid retention or heart failure.
Gastrointestinal (GI) Effects Risk of GI Ulceration, Bleeding, and Perforation
NSAIDs, including diclofenac sodium delayed-release tablets, can cause serious gastrointestinal (GI) adverse events including inflammation, bleeding, ulceration, and perforation of the stomach, small intestine, or large intestine, which can be fatal. These serious adverse events can occur at any time, with or without warning symptoms, in patients treated with NSAIDs. Only one in five patients, who develop a serious upper GI adverse event on NSAID therapy, is symptomatic. Upper GI ulcers, gross bleeding, or perforation caused by NSAIDs occur in approximately 1% of patients treated for 3-6 months, and in about 2-4% of patients treated for one year. These trends continue with longer duration of use, increasing the likelihood of developing a serious GI event at some time during the course of therapy. However, even short-term therapy is not without risk.

NSAIDs should be prescribed with extreme caution in those with a prior history of ulcer disease or gastrointestinal bleeding. Patients with a prior history of peptic ulcer disease and/or gastrointestinal bleeding who use NSAIDs have a greater than 10-fold increased risk for developing a GI bleed compared to patients with neither of these risk factors. Other factors that increase the risk for GI bleeding in patients treated with NSAIDs include concomitant use of oral corticosteroids or anticoagulants, longer duration of NSAID therapy, smoking, use of alcohol, older age, and poor general health status. Most spontaneous reports of fatal GI events are in elderly or debilitated patients and therefore, special care should be taken in treating this population.

To minimize the potential risk for an adverse GI event in patients treated with an NSAID, the lowest effective dose should be used for the shortest possible duration. Patients and physicians should remain alert for signs and symptoms of GI ulceration and bleeding during NSAID therapy and promptly initiate additional evaluation and treatment if a serious GI adverse event is suspected. This should include discontinuation of the NSAID until a serious GI adverse event is ruled out. For high risk patients, alternate therapies that do not involve NSAIDs should be considered.
Renal Effects
Caution should be used when initiating treatment with diclofenac sodium delayed-release tablets in patients with considerable dehydration.

Long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury. Renal toxicity has also been seen in patients in whom renal prostaglandins have a compensatory role in the maintenance of renal perfusion. In these patients, administration of a nonsteroidal anti-inflammatory drug may cause a dose-dependent reduction in prostaglandin formation and, secondarily, in renal blood flow, which may precipitate overt renal decompensation. Patients at greatest risk of this reaction are those with impaired renal function, heart failure, liver dysfunction, those taking diuretics and ACE inhibitors, and the elderly. Discontinuation of NSAID therapy is usually followed by recovery to the pretreatment state.
Advanced Renal Disease
No information is available from controlled clinical studies regarding the use of diclofenac sodium delayed-release tablets in patients with advanced renal disease. Therefore, treatment with diclofenac sodium delayed-release tablets are not recommended in these patients with advanced renal disease. If diclofenac sodium delayed-release tablets therapy must be initiated, close monitoring of the patient’s renal function is advisable.
Anaphylactoid Reactions
As with other NSAIDs, anaphylactoid reactions may occur in patients without known prior exposure to diclofenac sodium delayed-release tablets. Diclofenac sodium delayed-release tablets should not be given to patients with the aspirin triad. This symptom complex typically occurs in asthmatic patients who experience rhinitis with or without nasal polyps, or who exhibit severe, potentially fatal bronchospasm after taking aspirin or other NSAIDs (see CONTRAINDICATIONS and PRECAUTIONS: Preexisting Asthma .) Emergency help should be sought in cases where an anaphylactoid reaction occurs.
Skin Reactions
NSAIDs, including diclofenac sodium delayed-release tablets, can cause serious skin adverse events such as exfoliative dermatitis, Stevens-Johnson Syndrome (SJS), and toxic epidermal necrolysis (TEN), which can be fatal. These serious events may occur without warning. Patients should be informed about the signs and symptoms of serious skin manifestations and use of the drug should be discontinued at the first appearance of skin rash or any other sign of hypersensitivity.
Pregnancy
In late pregnancy, as with other NSAIDs, diclofenac sodium delayed-release tablets should be avoided because it may cause premature closure of the ductus arteriosus.