Diclofenac
2-(2-(2,6-dichlorophenylamino)phenyl)acetic acid

Cataflam 為內含鉀鹽的 diclofenac，是一種非類固醇成分，具抗發炎、鎮痛、及退燒等特性。
實驗已證實其基本作用機轉為抑制前列腺素的生合成。在形成發炎、疼痛、與發燒的過程中，前列腺素扮演著主要的角色。
體外試驗中，與人體內相同濃度的 diclofenac potassium，並不會抑制軟骨中蛋白多醣 (proteoglycan) 的生合成。

Absorption
Bioavailability is approximately 50% because of first-pass metabolism (oral doseforms). Food decreases T max and C max .

Immediate-release tablets
T max is approximately 1 h.

Extended-release (ER) tablets
T max is approximately 5.3 h.

Delayed-release tablets (50 mg dose)
T max is approximately 2.3 h.

Solaraze topical gel
Following application of 2 g 3 times daily for 6 days, mean AUC is 9 ng•h/mL, mean C max is 4 ng/mL, and mean T max is 4.5 h.

Topical patch
Following a single application of the patch on the upper inner arm, C max of 0.7 to 6 ng/mL was noted between 10 and 20 h of application. With twice-daily application of patch, plasma concentrations ranged from 1.3 to 8.8 ng/mL after 5 days.

Voltaren gel
C max with application of 160 mg/day is 15 ng/mL and 54 ng/mL with application of 480 mg/day. T max is 14 h with the application of 160 mg/day and 10 h with the application of 480 mg/day. The amount reaching the systemic circulation is 158 times lower with 160 mg/day compared with oral treatment.

Distribution
More than 99% protein bound (albumin). Vd is approximately 1.4 L/kg (oral).

Metabolism
Undergoes hepatic metabolism; metabolized to 5 metabolites.

Elimination
Approximately 65% is excreted in urine and 35% in the bile. The t ½ is 1 to 2 h. Plasma elimination t ½ after application of topical patch is approximately 12 h.

Special Populations
Renal Function Impairment
No differences in pharmacokinetics have been detected in studies with patients with renal function impairment.

Hepatic Function Impairment
Since hepatic metabolism accounts for 100% of diclofenac elimination, patients with hepatic disease may require reduced doses.

ACE inhibitors
Antihypertensive effect of ACE inhibitors may be diminished.

Aminoglycosides (eg, gentamicin)
Aminoglycoside concentrations may be elevated, increasing the risk of adverse reactions.

Aspirin
Protein binding of diclofenac may be reduced; in addition, the risk of gastric erosion and bleeding may be increased.

Azole antifungal agents (eg, fluconazole)
Diclofenac plasma concentrations may be elevated, increasing the risk of adverse reactions.

Bisphosphonates (eg, alendronate)
Coadministration may increase the risk of gastric ulceration.

Cyclosporine
May increase nephrotoxicity.

Digoxin
May increase digoxin serum concentrations.

Furosemide and thiazide diuretics
May inhibit diuretic and antihypertensive effects.

Heparin
Risk of hemorrhagic adverse reactions may be increased.

Lithium
May decrease lithium Cl.

Methotrexate
May increase methotrexate levels.

SSRIs (eg, fluoxetine)
Risk of upper GI bleeding may be increased.

Warfarin
May increase risk of gastric erosion and bleedi

1.治療期間發生胃出血等潰瘍應停藥。
2.對老年患者之用藥應特別小心體虛或體重過輕者應使用最低有效劑量。
3.可能導致肝功能酵素值升高故長期使用者須監測肝功能。