General Information

Pennsaid is a topical formulation of diclofenac sodium in a patented carrier solution. The drug combines a transdermal carrier with diclofenac sodium, a nonsteroidal anti-inflammatory drug, and delivers the active drug through the skin directly to the pain site.

Pennsaid is specifically indicated for the treatment of signs and symptoms of osteoarthritis of the knee(s).

Pennsaid is supplied as a 1.5% solution designed for topical administration. The recommended initial dose of the drug is 40 drops per knee, 4 times a day. Pennsaid should be spread evenly around front, back and sides of the knee, 10 drops at a time. Repeat this procedure until 40 drops have been applied and the knee is completely covered with solution.

Clinical Results

FDA Approval
The FDA approval of Pennsaid was based on two double-blind controlled trials conducted in the US and Canada. The subjects were treated with placebo, another NSAID or Pennsaid Topical Solution at a dose of 40 drops four times a day for 12 weeks. In both trials, Pennsaid treatment resulted in statistically significant clinical improvement compared to placebo and/or vehicle, in all three primary efficacy variables: pain (WOMAC pain score), physical function (WOMAC physical function) and patient overall health assessment (POHA). The results were as follows:

Study One
WOMAC pain Score: Baseline score: 13. After 12 weeks of treatment, the mean change in score was -6.0 (Pennsaid); -4.7 (placebo) and -4.7 (vehicle).
WOMAC physical Baseline score: 42. After 12 weeks of treatment, the mean change in score was -15.7 (Pennsaid); -12.3 (placebo) and -12.1 (vehicle).
POHABaseline score: 2.3 After 12 weeks of treatment, the mean change in score was -1.0 (Pennsaid); -0.4 (placebo) and -0.6 (vehicle).

Study Two
This study only compared Pennsaid to an NSAID. WOMAC pain Score: Baseline score: 13. After 12 weeks of treatment, the mean change in score was -5.9 (Pennsaid); -4.4 (vehicle).
WOMAC physical Baseline score: 42. After 12 weeks of treatment, the mean change in score was -15.3 (Pennsaid) and -10.3 (vehicle).
POHABaseline score: 3.1 After 12 weeks of treatment, the mean change in score was -1.3 (Pennsaid) and -1.0 (vehicle).

Mechanism of Action

Pennsaid is a topical formulation of diclofenac sodium in a patented carrier solution. The mechanism of action of diclofenac is similar to that of other nonsteroidal anti-inflammatory drugs. Diclofenac inhibits the enzyme, cyclooxygenase (COX), an early component of the arachidonic acid cascade, resulting in the reduced formation of prostaglandins, thromboxanes and prostacylin. It is not completely understood how reduced synthesis of these compounds results in therapeutic efficacy.

Literature References

Hui X, Hewitt PG, Poblete N, Maibach HI, Shainhouse JZ, Wester RC In vivo bioavailability and metabolism of topical diclofenac lotion in human volunteers. Pharmaceutical Research 1998 Oct;15(10):1589-95

Tugwell PS, Wells GA, Shainhouse JZ Equivalence study of a topical diclofenac solution (pennsaid) compared with oral diclofenac in symptomatic treatment of osteoarthritis of the knee: a randomized controlled trial. The Journal of Rheumatology 2004 Oct;31(10):2002-12.

Roth SH, Shainhouse JZ Efficacy and safety of a topical diclofenac solution (pennsaid) in the treatment of primary osteoarthritis of the knee: a randomized, double-blind, vehicle-controlled clinical trial. Archives of Internal Medicene 2004 Oct 11;164(18):2017-23

Baer PA, Thomas LM, Shainhouse Z Treatment of osteoarthritis of the knee with a topical diclofenac solution: a randomised controlled, 6-week trial [ISRCTN53366886]. BMC Musculoskeletal Disorders 2005 Aug 8;6:44

Towheed TE Pennsaid therapy for osteoarthritis of the knee: a systematic review and metaanalysis of randomized controlled trials. The Journal of Rheumatology 2006 Mar;33(3):567-73