The aim of this randomized, single-blind, active-controlled pilot study was to investigate the clinical efficacy of oral supplementation with Verbascox®, a proprietary herbal extract capable of inhibiting human
cyclooxygenase-2 (COX-2), in patients with mild-to-moderate
osteoarthritis (OA) of the knee. Patients in the control group (n = 50) did not undergo any treatment (watchful waiting). Patients in the Verbascox® group (n = 50) received oral supplementation (800 mg/day) with the herbal extract for 2 weeks. The final study group consisted of patients (n = 50) who received
celecoxib, a known pharmacological inhibitor of COX-2, 200 mg/day for 2 weeks. Examining physicians and laboratory personnel were blinded to group assignment, whereas patients were unblinded. All participants were evaluated using standard measures of
pain relief and improvement in functional capacity at baseline, after 1 week, and at the end of the 2-week treatment course. Moreover, serum levels of
substance P (SP), a member of the
tachykinin family of
neuropeptides involved in pain perception, were measured at the three time points. Both Verbascox® and
celecoxib reduced
pain, improved functional capacity, and lowered serum SP levels at 2 weeks compared with baseline, without significant inter-arm differences. Both Verbascox® and
celecoxib showed a limited number of treatment-emergent adverse events. In summary, oral supplementation with Verbascox® (800 mg/day) in patients with mild-to-moderate OA of the knee is as effective and safe as a standard therapeutic dose of
celecoxib in terms of
pain relief and improvement in functional capacity after a 2-week treatment course.