Is acne an infection of blocked pilosebaceous follicles? Implications for antimicrobial treatment

Efficacy assessments of tretinoin-loaded nano lipid carriers in acne vulgaris: a double blind, split-face randomized clinical study

Here, we assessed the efficacy and safety of Nano lipid carrier (NLC) drug delivery system containing tretinoin (NLC-TRE) in comparison with the conventional 0.05% tretinoin cream (TRE cream) in mild to moderate acne vulgaris. A stable and appropriate NLC-TRE formulation was prepared using a high-pressure homogenizer and particle characterization and physicochemical properties were evaluated under accelerated conditions. Efficacy assessment was performed via a split-face clinical study, by comparing the number of acne lesions, porphyrin production and skin biophysical parameters in both sides of the face randomly treated with NLC-TRE and TRE cream. Plasma concentration of tretinoin after topical application of NLC-TRE was measured for primary safety evaluation. We acquired a stable, spherical nanoparticles with particle size of 118.5 nm, PI equal to 0.485 and ZP of - 44.7 mV. The rate of decrease of acne lesions was significantly higher in NLC- TRE side (p value < 0.001). The size and intensity of porphyrin production in pilosebaceous follicles were significantly reduced only on NLC-TRE side (p value < 0.01). The plasma concentration of the tretinoin, after 8 weeks' application remained lower than the toxic levels. The NLC-TRE formula provides better efficiency and good loading capacity of TRE in the drug delivery system.

Do tetracyclines and erythromycin exert anti-acne effects by inhibition of P450-mediated degradation of retinoic acid?

For decades, retinoic acid (RA) is known as the most potent therapeutic option in the therapy of acne and altered homeostasis of endogenous retinoids has been discussed in the context of acne pathogenesis. Besides retinoids, antibiotics such as tetracyclines or erythromycin are well established in acne pharmacotherapy. Accumulating evidence points towards common molecular pathways being targeted by both RA and anti-acne antibiotics; however, a precise 'common denominator' connecting these chemically diverse anti-acne agents has not yet been identified. Interestingly, tetracyclines are associated with the occurrence of pseudotumor cerebri, a rare neurological side effect otherwise associated with retinoid intoxication or RA exposure. This association at the clinical level suggests an interaction between tetracyclines and endogenous RA signalling. As erythromycin does not cross the blood brain barrier, CNS side effects are not to be expected, yet not precluding a possible local interaction of erythromycin with endogenous RA metabolism in the skin. We hypothesize tetracyclines and erythromycin to locally inhibit endogenous RA metabolism in the skin and thus mimic therapeutic action of RA. This readily testable hypothesis suggests inhibition of endogenous RA metabolism and amplification of endogenous RA signalling as a mechanism underlying the biochemical actions of antibiotics in acne therapy. Elucidation of such interactions may ultimately enhance our understanding of acne therapy and pathogenesis and may yield a sound, scientific basis for hypothesis-driven development of novel therapeutic compounds.

Minocycline in acne vulgaris: benefits and risks

Minocycline is a semi-synthetic, second-generation tetracycline. It was introduced in 1972 and has both antibacterial and anti-inflammatory properties. Minocycline is used for a variety of infectious diseases and in acne. Even today, new indications beyond the antibacterial indications are being investigated such as its use in neurologic diseases. Formerly, minocycline was thought to have a superior efficacy in the treatment of inflammatory acne, especially with respect to antibacterial-resistant Propionibacterium acnes. A thorough review of the literature, however, shows that minocycline is not more effective in acne than other tetracyclines. Compared with first-generation tetracyclines, minocycline has a better pharmacokinetic profile, and compared with doxycycline it is not phototoxic. However, minocycline has an increased risk of severe adverse effects compared with other tetracyclines. It may induce hypersensitivity reactions affecting the liver, lung, kidneys, or multiple organs (Drug Reaction with Eosinophilia and Systemic Symptoms [DRESS] syndrome) in the first weeks of treatment and, with long-term treatment, may cause autoimmune reactions (systemic lupus erythematosus, autoimmune hepatitis). In addition, CNS symptoms, such as dizziness, are more frequent compared with other tetracyclines. Long-term treatment may induce hyperpigmentation of the skin or other organs. Resistance of P. acnes to minocycline also occurs, dependent on the prescribing behavior. Considering the aspects of efficacy, its adverse effect profile, resistance, price, and alternatives, minocycline is no longer considered the first-line antibacterial in the treatment of acne.

Skin capacitance imaging of acne lesions

BACKGROUND

Little information is available about specific functional characteristics of skin in acneic patients.

OBJECTIVE

To determine a capacitance mapping of lesional skin in acne in order to predict drug affinity according to the hydrophilic-lipophilic characteristics.

METHOD

Skin capacitance imaging based on silicon image sensor technology was used with the SkinChip device.

RESULTS

The non-optical images obtained by this means clearly identified low capacitance comedones contrasting with a perifollicular rim of high capacitance in inflammatory papules. This method also showed sweating and the follicular pores distributed in a pinpoint pattern.

CONCLUSION

The objective mapping of skin surface capacitance showed large differences between acne lesions and the surrounding skin. The low capacitance of comedones contrasted with the high capacitance of the perifollicular area in inflammatory papules. These electrometric characteristics reflecting the corneocyte hydration may influence drug affinity to acne lesions.

Comparison of five antimicrobial regimens for treatment of mild to moderate inflammatory facial acne vulgaris in the community: randomised controlled trial

BACKGROUND

We investigated the efficacy and cost-effectiveness of five antimicrobial regimens for mild to moderate facial acne and whether propionibacterial antibiotic resistance affects treatment response.

METHODS

In this randomised, observer-masked trial, 649 community participants were allocated one of five antibacterial regimens. Primary outcomes were patients' self-assessed improvement and reduction in inflamed lesions at 18 weeks. Analyses were by intention to treat.

FINDINGS

Moderate or greater improvement at 18 weeks was reported in 72 (55%) of 131 participants assigned oral oxytetracycline plus topical placebo, 70 (54%) of 130 assigned oral minocycline plus topical placebo, 78 (60%) of 130 assigned topical benzoyl peroxide plus oral placebo, 84 (66%) of 127 assigned topical erythromycin and benzoyl peroxide in a combined formulation plus oral placebo, and 82 (63%) of 131 assigned topical erythromycin and benzoyl peroxide separately plus oral placebo. Most improvement occurred in the first 6 weeks. Treatment differences for the proportion of people with at least moderate improvement were: minocycline versus oxytetracycline -1.2% (unadjusted 95% CI -13.3 to 10.9); combined erythromycin and benzoyl peroxide versus oxytetracycline 11.1% (-0.7 to 22.9) and versus minocycline 12.3% (0.4 to 24.2); erythromycin and benzoyl peroxide separately versus combined formulation -3.5% (-15.2 to 8.2); benzoyl peroxide versus oxytetracycline 5.0% (-7.0 to 17.0), versus minocycline 6.2% (-5.8 to 18.2), and versus combined formulation -6.1% (-17.9 to 5.7). Benzoyl peroxide was the most cost-effective treatment. Efficacy of both tetracyclines was reduced by pre-existing tetracycline resistance.

INTERPRETATION

Topical benzoyl peroxide and benzoyl peroxide/erythromycin combinations are similar in efficacy to oral oxytetracycline and minocycline and are not affected by propionibacterial antibiotic resistance.

Systemic therapy for acne vulgaris

There are three main groups of systemic therapies available for the treatment of acne vulgaris: systemic antibiotics, hormonal therapy (for females) and oral isotretinoin. This article outlines when these treatments should be prescribed for the treatment of acne, considers the impact of therapy on aetiology, and advises on dosage regimens, potential adverse effects and expected efficacy.

Site-specific methylene blue delivery to pilosebaceous structures using highly porous nylon microspheres: an experimental evaluation

PURPOSE

This study aimed to evaluate the penetration of methylene blue (MB)-loaded microspheres into pilosebaceous structures of rats.

MATERIALS AND METHODS

MB was incorporated into 5 microm highly porous nylon microspheres. The microspheres were dispersed into fluid silicone. Male hairless rats were used to evaluate the penetration of MB into hair follicles. After formulation application, MB diffusion was induced and skin biopsies were realized immediately, 2 and 26 hours after MB loaded microspheres application. MB fluorescence was observed with a microscope expanded for fluorescence microscopy.

RESULTS

Position of microspheres and MB diffusion was dependent on delay between microspheres application and harvest. Inside the skin, MB was seen exclusively in the hair follicle and the sebaceous glands. MB diffusion varied from 160+/-50 microm (2 hours after application) to 410+/-70 microm (26 hours after application). MB was also found in the sebaceous glands.

DISCUSSION

This study confirms that 5 micro m microspheres are optimally deposited deep within the pilosebaceous structure. In agreement with the literature, when microspheres are topically applied on the skin, they penetrate via a "lipid-rich channel" coating the hair follicles. MB is exclusively distributed in the hair follicles and their accessories.

CONCLUSION

This report presents evidence of MB pilosebaceous delivery through the use of microsphere formulation. This is obtained thanks to topical enhancement via the follicular route. This drug delivery system aims to transport MB into the pilosebaceous unit specifically and deeply. Various other applications could derive from this work. For example, such a method might be used to increase the therapeutic index of drugs directed at hair sebaceous gland disorders. Laser treatment of acne or laser hair removal could also benefit of this technique.

The rationale for using a topical retinoid for inflammatory acne

Both comedogenesis and the development of inflammatory lesions in acne vulgaris appear to be related to genetic as well as immune processes. The key regulatory cytokine, interleukin-1alpha, has recently been documented as playing a major role in both the hypercornification and the orchestration of immune factors, ultimately resulting in noninflammatory and inflammatory lesions. Topical retinoids, such as tretinoin, and topical retinoid analogs, such as adapalene and tazarotene, help normalize the abnormal follicular keratinocyte desquamation - a key pathophysiologic factor in comedogenesis. This normalization also helps mitigate against the development of a propitious microenvironment for Propionibacterium acnes. Preclinical data suggest that topical retinoids and retinoid analogs may also have direct anti-inflammatory effects. A wealth of clinical data confirms that topical retinoids and retinoid analogs significantly reduce inflammatory lesions. Comparative clinical trials also demonstrate that adapalene has the best cutaneous tolerability profile of all these agents. Optimal therapy for inflammatory acne would involve the use of topical retinoids or retinoid analogs combined with oral or topical antibacterials.