Topical capsaicin has been introduced in the U.S. and Canada as a cream indicated for temporary relief of neuralgia following episodes of herpes zoster infections and in the treatment of diabetic neuropathy. Although capsaicin is clinically used as an external analgesic for temporary relief of neuralgia, it has also been widely used as a research tool to study peripheral pain. Capsaicin apparently works to release substance P from sensory nerve fibers and after repeated applications, depletes neurons of substance P. Clinical investigations of topical capsaicin include trials in chronic pain syndromes such as postherpetic neuralgia, postmastectomy neuroma, reflex sympathetic dystrophy syndrome, diabetic neuropathy, rheumatoid arthritis, psoriasis, hemodialysis-associated itching, and vulvar vestibulitis. In addition, therapeutic benefits of capsaicin cream on apocrine chromhidrosis have been described. Further clinical studies are warranted in several of these conditions to establish the efficacy of topical capsaicin. Serious or unexpected adverse reactions from clinical use have not been reported to date. Considering the paucity of safe and effective treatments for the conditions mentioned above, capsaicin cream appears to warrant further clinical investigations to establish its efficacy in a variety of chronic pain syndromes.

A dose-response effect has previously been demonstrated in topical minoxidil treatment of alopecia areata. Limitations in minoxidil solubility and percutaneous absorption have impaired the development of more effective topical therapy. Oral minoxidil (5 mg every 12 hours), a dose demonstrated to be relatively well tolerated if a 2-g sodium diet is strictly followed, was given to 65 patients with severe, treatment-resistant alopecia areata in an attempt to bypass the limitations of topical treatment and increase efficacy. Although hair regrowth progressed more rapidly and was more extensive with oral than topical 5% minoxidil, cosmetic response was seen only in 18% of the patients. Neither serum nor tissue levels of minoxidil correlated with response. These findings suggest that improved preparations of topical minoxidil, when used as a single therapeutic agent, are unlikely to be cosmetically effective in the majority of patients with severe alopecia areata.

Topical metronidazole gel (0.75%) was compared to placebo gel in a randomized, double-blind, placebo-controlled, split-face clinical trial for the treatment of 59 patients with acne rosacea. Statistically significant differences in inflammatory lesions, erythema, and global assessments were seen at three, six, and nine weeks post-baseline in favor of the active treatment side. It did not, however, alter the telangiectatic component of the disease. No known drug-related side effects were detected, and the low topical dose along with low serum levels of metronidazole indicate a high safety profile for this therapeutic agent. This work suggests that metronidazole gel, as specifically formulated, is safe and effective in reducing the symptomatology of acne rosacea.

A significant problem in the management of pediculosis is the removal of nits from the hair after pediculicide treatment. This study describes use of a nit removal system incorporating a cream rinse containing formic acid that loosens the bond between the nit and hair. Twenty-four children with pediculosis capitis, age 4 to 12 years, were evaluated. Sections of hair with equivalent numbers of nits were identified as control or test sites. Combining for 5 minutes after use of the formic acid rinse removed 93.5% of nits compared with a 27.6% reduction in the control section (p less than 0.0001). These results demonstrate that use of this nit removal system greatly facilitates nit removal.

Trichloroacetic acid (TCA) is a deliquescent chemical widely used for a variety of procedures. Stability of various concentrations of TCA in both amber glass and plastic bottles stored under refrigeration and at room temperature was measured at several time points. Extended stability data suggest that TCA potency is stable for 23 weeks and would best be maintained in glass amber bottles stored under refrigeration.