Carcinogenicity studies in mice and rats administered diclofenac sodium, as a dietary constituent for 2 years resulted in no significant increases in tumor incidence at doses up to 2 mg/kg/day corresponding to approximately 0.35-and 0.7-fold (mouse and rat, respectively) of the maximum recommended human topical dose (MRHD) of diclofenac sodium topical solution (based on apparent bioavailability and body surface area comparison).
In a dermal carcinogenicity study conducted in albino mice, daily topical applications of diclofenac sodium for two years at concentrations up to 0.035% diclofenac sodium (a 43-fold lower diclofenac sodium concentration than present in diclofenac sodium topical solution) did not increase neoplasm incidence.
In a photococarcinogenicity study conducted in hairless mice, topical application of diclofenac sodium at doses up to 0.035% diclofenac sodium (a 43-fold lower diclofenac sodium concentration than present in diclofenac sodium topical solution) resulted in an earlier median time of onset of tumors.
Mutagenesis: Diclofenac was not mutagenic or clastogenic in a battery of genotoxicity tests that included the bacterial reverse mutation assay, in vitro mouse lymphoma point mutation assay, chromosomal aberration studies in Chinese hamster ovarian cells in vitro, and in vivo rat chromosomal aberration assay of bone marrow cells.
Impairment of Fertility: Fertility studies have not been conducted with diclofenac sodium topical solution. Diclofenac sodium administered to male and female rats at doses up to 4 mg/kg/day (1.4-fold of the MRHD of diclofenac sodium topical solution based on apparent bioavailability and body surface area comparison) did not affect fertility. Studies have not been conducted to determine the safety of DMSO on fertility.
No adverse effects were observed using indirect ophthalmoscopy after multiple-daily dermal application to rats for 26 weeks and minipigs for 52 weeks of DMSO at twice the concentration found in diclofenac sodium topical solution. Published studies of dermal or oral administration of DMSO to rabbits, dogs and pigs described refractive changes of lens curvature and cortical fibers indicative of myopic changes and/or incidences of lens opacity or discoloration when evaluated using slit-lamp biomicroscopy examination, although no ocular abnormalities were observed in rhesus monkeys during daily oral or dermal treatment with DMSO for 9 to 18 months.
The use of diclofenac sodium topical solution for the treatment of the signs and symptoms of osteoarthritis of the knee was evaluated in two double-blind controlled trials conducted in the U.S. and Canada, involving patients treated with diclofenac sodium topical solution at a dose of 40 drops four times a day for 12 weeks. Diclofenac sodium topical solution was compared to topical placebo (2.3% DMSO with other excipients) and/or topical vehicle solution (45.5% w/w DMSO with other excipients), applied directly to the study knee. In both trials, diclofenac sodium topical solution treatment resulted in statistically significant clinical improvement compared to placebo and/or vehicle, in all three primary efficacy variables – pain, physical function (Western Ontario and McMaster Universities LK3.1 OA Index (WOMAC) pain and physical function dimensions) and Patient Overall Health Assessment (POHA)/Patient Global Assessment (PGA). Numerical results are summarized in Tables 3 and 4.
|Efficacy Variable||Study I Mean baseline score and mean change in efficacy variables after 12 weeks of treatment|
|Mean Baseline score||Diclofenac sodium N=154||Topical placebo *N=155||Topical vehicle †N=161|
|WOMAC pain score (Likert 3.1, 0-20)||13||-6.0||-4.7||-4.7|
|WOMAC physical function (Likert 3.1, 0-68)||42||-15.7||-12.3||-12.1|
|Efficacy Variable||Study II Mean baseline score and mean change in efficacy variables after 12 weeks of treatment|
|Mean Baseline score||Diclofenac sodium N=164||Topical vehicle *N=162|
|WOMAC pain score (Likert 3.1, 0-20)||13||-5.9||-4.4|
|WOMAC physical function (Likert 3.1, 0-68)||42||-15.3||-10.3|
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