Imiquimod may aid tattoo removal

Key Points

Galveston, Texas - Topical imiquimod 5 percent cream (Aldara, 3M Pharmaceuticals) appears to be a useful adjuvant to laser removal of mature tattoos in guinea pigs, according to a recent study.

But whether the treatment can aid humans remains to be seen, the study's lead researcher adds.

"Tattoo removal is not entirely the result of immunologic-mediated clearing of pigment. There's more to it than that," says Mark A. Ramirez, M.D., chief resident in dermatology, University of Texas Medical Branch, Galveston.

"If one stimulates macrophages, which are part of the immune system, one can essentially wake them up and help them get rid of the pigment" at targeted sites, Dr. Ramirez says. In contrast, fibroblasts remain stationary.

And unless the pigment is drained from tattoo sites, some residual ink will remain.

"We know that imiquimod enhances our immune system to migrate to areas where it's applied," he adds.

TATTOOED GUINEA PIGS

Following Institutional Animal Care and Use Committee approval, researchers anesthetized and tattooed 14 male albino guinea pigs with black ferrous oxide ink using a professional tattoo machine (Huck Spaulding Enterprises, Voorheesville, N.Y.,) to a depth of approximately 1 mm.

Researchers then allowed the 1 cm-by-3 cm tattoos to mature for four weeks.

Next, investigators randomized half the guinea pigs to the treatment group; the rest served as controls. Researchers anesthetized and shaved each guinea pig before treating it with a Q-switched alexandrite laser system (Schwartz Electro-optics) set at 755 nm with a 100 ns to 120 ns pulse duration. Treatment parameters also included 4 J/cm² to 6.5 J/cm² fluences and 2 mm to 3 mm spot sizes.

Researchers then treated the experimental group triweekly with topical imiquimod cream beginning immediately after laser treatment and for a duration of three weeks. At week six, investigators again shaved and photographed tattoo areas before performing a second laser treatment. They continued this regimen for a total of six laser sessions spaced four to six weeks apart, followed by imiquimod application as above in the experimental group.

Five weeks after the last treatment session, researchers took clinical photographs and 4 mm punch biopsies from specimens. A blinded dermatopathologist provided histologic evaluation, assigning a 0 to 4 rating based on the amount of ink present. Other parameters evaluated included the predominant location of remaining pigment, presence of inflammation and degree of fibrosis. Additionally, four blinded dermatologists made final clinical assessments of post-treatment photographs using an ascending five-point scale.

DEPIGMENTED PIGS

Overall, physicians rated members of the imiquimod-treated group as having less clinically apparent pigment than most of the tattoos treated with lasers alone (p=0.012; Dermatol Surg. 2007;33:319-325).

Among this group, two tattoos appeared virtually pigment-free, while one-third earned scores of 0 from three evaluators and 2 from the fourth evaluator (mean: 0.5).

Throughout treatment, side effects, including erythema, induration and minute epidermal disruptions, occurred slightly more often among the imiquimod-treated group. Moreover, hematoxylin and eosin-stained biopsy specimens of tattoos in this group showed significantly less pigment, Dr. Ramirez says. In particular, the average histologic pigment rating among treated tattoos was 1.3 versus 2.2 in the control group. As researchers expected, histologic ratings of inflammation and fibrosis were somewhat higher in the treated group.

"The best pigment-clearing results also had the most inflammation and scarring," he says. Therefore, Dr. Ramirez says that, in some respects, the treatment "trades tattoo for some scar tissue."

PROS, CONS AND CONCERNS

To maximize clearing of tattoo pigment, he says, "One probably must produce at least some scarring."