Pharmacodynamics

Flector® Patch applied to intact skin provides local analgesia by releasing diclofenac epolamine from the patch into the skin. Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID). In pharmacologic studies, diclofenac has shown anti-inflammatory, analgesic, and antipyretic activity. As with other NSAIDs, its mode of action is not known; its ability to inhibit prostaglandin synthesis, however, may be involved in its anti-inflammatory activity, as well as contribute to its efficacy in relieving pain associated with inflammation.

Pharmacokinetics

Absorption

Following a single application of the Flector® Patch on the upper inner arm, peak plasma concentrations of diclofenac (range 0.7 – 6 ng/mL) were noted between 10 – 20 hours of application. Plasma concentrations of diclofenac in the range of 1.3 – 8.8 ng/mL were noted after five days with twice-a-day Flector® Patch application.

Systemic exposure (AUC) and maximum plasma concentrations of diclofenac, after repeated dosing for four days with Flector® Patch, were lower ( < 1%) than after a single oral 50-mg diclofenac sodium tablet.

The pharmacokinetics of Flector® Patch has been tested in healthy volunteers at rest or undergoing moderate exercise (cycling 20 min/h for 12 h at a mean HR of 100.3 bpm). No clinically relevant differences in systemic absorption were observed, with peak plasma concentrations in the range of 2.2 – 8.1 ng/mL while resting, and 2.7 – 7.2 ng/mL during exercise.

Distribution

Diclofenac has a very high affinity ( > 99%) for human serum albumin.

Metabolism and Excretion

The plasma elimination half-life of diclofenac after application of Flector® Patch is approximately 12 hours. Diclofenac is eliminated through metabolism and subsequent urinary and biliary excretion of the glucuronide and the sulfate conjugates of the metabolites.

Clinical Studies

Efficacy of Flector® Patch was demonstrated in two of four studies of patients with minor sprains, strains, and contusions. Patients were randomly assigned to treatment with the Flector® Patch, or a placebo patch identical to the Flector® Patch minus the active ingredient. In the first of these two studies, patients with ankle sprains were treated once daily for a week. In the second study, patients with sprains, strains and contusions were treated twice daily for up to two weeks. Pain was assessed over the period of treatment. Patients treated with the Flector® Patch experienced a greater reduction in pain as compared to patients randomized to placebo patch as evidenced by the responder curves presented below.

Figure 1: Patients Achieving Various Levels of Pain Relief at Day 3; 14-Day Study

Figure 2: Patients Achieving Various Levels of Pain Relief at End of Study; 14-Day Study

Figure 3: Patients Achieving Various Levels of Pain Relief at Day 3; 7-Day Study

Figure 4: Patients Achieving Various Levels of Pain Relief at End of Study; 7-Day Study

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