Spotlight on topical pimecrolimus in atopic dermatitis

Polymeric Nanoparticles as Tunable Nanocarriers for Targeted Delivery of Drugs to Skin Tissues for Treatment of Topical Skin Diseases

The topical route is the most appropriate route for the targeted delivery of drugs to skin tissues for the treatment of local skin diseases; however, the stratum corneum (SC), the foremost layer of the skin, acts as a major barrier. Numerous passive and active drug delivery techniques have been exploited to overcome this barrier; however, these modalities are associated with several detrimental effects which restrict their clinical applicability. Alternatively, nanotechnology-aided interventions have been extensively investigated for the topical administration of a wide range of therapeutics. In this review, we have mainly focused on the biopharmaceutical significance of polymeric nanoparticles (PNPs) (made from natural polymers) for the treatment of various topical skin diseases such as psoriasis, atopic dermatitis (AD), skin infection, skin cancer, acute-to-chronic wounds, and acne. The encapsulation of drug(s) into the inner core or adsorption onto the shell of PNPs has shown a marked improvement in their physicochemical properties, avoiding premature degradation and controlling the release kinetics, permeation through the SC, and retention in the skin layers. Furthermore, functionalization techniques such as PEGylation, conjugation with targeting ligand, and pH/thermo-responsiveness have shown further success in optimizing the therapeutic efficacy of PNPs for the treatment of skin diseases. Despite enormous progress in the development of PNPs, their clinical translation is still lacking, which could be a potential future perspective for researchers working in this field.

A randomized study of the safety, absorption and efficacy of pimecrolimus cream 1% applied twice or four times daily in patients with atopic dermatitis

BACKGROUND

Pimecrolimus cream 1% (Elidel), a non-steroid inhibitor of inflammatory cytokines, is effective in the treatment of atopic dermatitis, without corticosteroid-related side effects such as skin atrophy. It is indicated for twice-daily application. More frequent applications might be expected either to enhance efficacy or increase toxicity. This study compared the safety, efficacy and systemic absorption of pimecrolimus administered twice daily (recommended dose) and four times daily early in the treatment of patients with moderate to severe atopic dermatitis.

METHODS

Adolescent and adult patients with moderate to severe atopic dermatitis were randomly assigned to a twice daily (BID) treatment group (n = 24) or a four times daily (QID) group (n = 25). During days 1-7, patients in the QID group applied pimecrolimus four times daily, and patients in the BID group applied pimecrolimus twice daily plus vehicle equivalent twice daily. During days 8-21, all patients were required to use pimecrolimus twice daily and had the option to use up to two further daily treatments (pimecrolimus in the QID group and vehicle equivalent in the BID group). Blood sampling occurred 2, 4, and 6 hours after the first morning application on days 1 and 5 and then prior to the first morning application on days 8 and 15, and any time on day 22.

RESULTS

Only 3 (12%) QID patients and 4 (17%) BID patients reported adverse events (primarily mild, transient application-site burning) with no significant difference between treatment groups in the frequency, type, or severity of adverse events. The median daily number of applications in the QID group during days 8-21 when two additional doses were optional remained at four. Pimecrolimus blood levels from a subgroup of 22 patients showed no difference in systemic exposure between the two dosing regimens. All but three (one in the QID group, two in the BID group) patients had blood levels below the limit of quantification; the highest single blood level of pimecrolimus measured in any patient was 1.37 ng/ml (QID group). Both the QID and BID regimens improved the signs and symptoms of atopic dermatitis similarly as measured by improvements in pruritus severity score, Investigator's Global Assessment, Eczema Area and Severity Index, percentage of body surface area affected, and patient's self-assessment of disease control.

CONCLUSIONS

The data suggest that increasing pimecrolimus application from twice daily to four times daily to treat moderate to severe atopic dermatitis for up to 3 weeks does not alter the safety profile nor does it increase the efficacy of treatment. Systemic absorption of pimecrolimus applied BID and QID is minimal and is not different between dosing regimens. Patients and physicians familiar with the potential hazards of overuse of topical corticosteroids should be reassured that if pimecrolimus is applied at twice the recommended BID dose for short periods of time, there is no effect on safety, tolerability, or systemic absorption.