A comparative trial of two retinoids commonly used in the treatment of acne vulgaris

Antibacterial Activity of the Essential Oil From Litsea cubeba Against Cutibacterium acnes and the Investigations of Its Potential Mechanism by Gas Chromatography-Mass Spectrometry Metabolomics

Cutibacterium acnes (C. acnes) is an anaerobic Gram-positive bacterium generally considered as a human skin commensal, but is also involved in different infections, such as acne and surgical infections. Although there are a variety of treatments, the side effects and the problem of bacterial drug resistance still limit their clinical usage. In this study, we found that essential oil (EO) distilled from fresh mature Litsea cubeba possessed promising antibacterial activity against C. acnes. In order to elucidate its potential mechanism, bacteriostatic activity test, Live/Dead kit assay, scanning electron microscope (SEM), transmission electron microscope (TEM), and metabolomics were employed. In addition, the content of adenosine triphosphate (ATP) in bacterium and the activities of key enzymes involved in critical metabolic pathways were detected using a variety of biochemical assays. The results showed that EO exhibited significant antibacterial activity against C. acnes at a minimum inhibitory concentration (MIC) of 400 μg/mL and a minimum bactericidal concentration (MBC) of 800 μg/mL, and EO could destroy C. acnes morphology and inhibit its growth. Moreover, results from our study showed that EO had a significant effect on the C. acnes normal metabolism. In total, 86 metabolites were altered, and 34 metabolic pathways related to the carbohydrate metabolism, energy metabolism, amino acid metabolism, as well as cell wall and cell membrane synthesis were perturbed after EO administration. The synthesis of ATP in bacterial cells was also severely inhibited, and the activities of key enzymes of the glycolysis and Wood-Werkman cycle were significantly affected (Pyruvate Carboxylase, Malate Dehydrogenase and Pyruvate kinase activities were decreased, and Hexokinase was increased). Taken together, these results illustrated that the bacteriostatic effect of EO against C. acnes by breaking the bacterial cell morphology and perturbing cell metabolism, including inhibition of key enzyme activity and ATP synthesis. The results from our study may shed new light on the discovery of novel drugs with more robust efficacy.

Topical preparations for the treatment of mild-to-moderate acne vulgaris: systematic review and network meta-analysis

BACKGROUND

Acne is very common and can have a substantial impact on wellbeing. Guidelines suggest first-line management with topical treatments, but there is little evidence regarding which treatments are most effective.

OBJECTIVES

To identify the most effective and best tolerated topical treatments for acne using network meta-analysis.

METHODS

CENTRAL, MEDLINE, Embase and World Health Organization Trials Registry were searched from inception to June 2020 for randomized trials that included participants with mild/moderate acne. Primary outcomes were self-reported improvement in acne, and trial withdrawal. Secondary outcomes included change in lesion counts, Investigator's Global Assessment, change in quality of life and total number of adverse events. Network meta-analysis was undertaken using a frequentist approach. Risk of bias was assessed using the Cochrane Risk of Bias Tool and confidence in evidence was assessed using CINeMA.

RESULTS

A total of 81 papers were included, reporting 40 trials with a total of 18 089 participants. Patient Global Assessment of Improvement was reported in 11 trials. Based on the pooled network estimates, compared with vehicle, benzoyl peroxide (BPO) was effective (35% vs. 26%) for improving self-reported acne. The combinations of BPO with adapalene (54% vs. 35%) or with clindamycin (49% vs. 35%) were ranked more effective than BPO alone. The withdrawal of participants from the trial was reported in 35 trials. The number of patients withdrawing owing to adverse events was low for all treatments. Rates of withdrawal were slightly higher for BPO with adapalene (2·5%) or clindamycin (2·7%) than BPO (1·6%) or adapalene alone (1·0%). Overall confidence in the evidence was low.

CONCLUSIONS

Adapalene in combination with BPO may be the most effective treatment for acne but with a slightly higher incidence of withdrawal than monotherapy. Inconsistent reporting of trial results precluded firmer conclusions.

Selective RAR agonists for acne vulgaris: A narrative review

BACKGROUND

Acne vulgaris is a chronic disfiguring inflammatory disease of adolescents and adults affecting up to 90% of the population around the world. The sequence of etiopathogenesis in acne is not completely understood but involves abnormalities in sebum production, follicular plugging, proliferation of propionibacterium acnes, and chronic inflammation.

AIMS

This review aims to summarize the features of the topical selective RAR agonists in treating acne vulgaris with a special emphasis on the 4th generation topical retinoid trifarotene.

METHODS

Studies were identified by searching electronic databases (MEDLINE and PubMed) till August 2019 and reference lists of respective articles. Only articles published in English language were included.

RESULTS

Topical retinoids have been first line of treatment for more than 30 years now in treating mild to moderate acne vulgaris. Third generation retinoids like adapalene and tazarotene are selective RAR and γ agonists, having an additional anti-inflammatory action along with their comedolytic effects and work well in combinations with topical antibiotics, due to the stability of chemical composition.

CONCLUSION

Trifarotene is a new 4th generation retinoid with selective action on RAR-γ receptor alone, which is specific for skin, and it is safe for long-term maintenance therapy with good efficacy and tolerability.

Retinoids: Literature Review and Suggested Algorithm for Use Prior to Facial Resurfacing Procedures

Vitamin A-containing products have been used topically since the early 1940s to treat various skin conditions. To date, there are four generations of retinoids, a family of Vitamin A-containing compounds. Tretinoin, all-trans-retinoic acid, is a first-generation, naturally occurring, retinoid. It is available, commercially, as a gel or cream. The authors conducted a complete review of all studies, clinical- and basic science-based studies, within the literature involving tretinoin treatment recommendations for impending facial procedures. The literature currently lacks definitive recommendations for the use of tretinoin-containing products prior to undergoing facial procedures. Tretinoin pretreatment regimens vary greatly in terms of the strength of retinoid used, the length of the pre-procedure treatment, and the ideal time to stop treatment before the procedure. Based on the current literature and personal experience, the authors set forth a set of guidelines for the use of tretinoin prior to various facial procedures.

In vivo treatment of Propionibacterium acnes infection with liposomal lauric acids

Propionibacterium acnes (P. acnes) is a Gram-positive bacterium strongly associated with acne infection. While many antimicrobial agents have been used in clinic to treat acne infection by targeting P. acnes, these existing anti-acne agents usually produce considerable side effects. Herein, the development and evaluation of liposomal lauric acids (LipoLA) is reported as a new, effective and safe therapeutic agent for the treatment of acne infection. By incorporating lauric acids into the lipid bilayer of liposomes, it is observed that the resulting LipoLA readily fuse with bacterial membranes, causing effective killing of P. acnes by disrupting bacterial membrane structures. Using a mouse ear model, we demonstrated that the bactericidal property of LipoLA against P. acne is well preserved at physiological conditions. Topically applying LipoLA in a gel form onto the infectious sites leads to eradication of P. acnes bacteria in vivo. Further skin toxicity studies show that LipoLA does not induce acute toxicity to normal mouse skin, while benzoyl peroxide and salicylic acid, the two most popular over-the-counter acne medications, generate moderate to severe skin irritation within 24 h. These results suggest that LipoLA hold a high therapeutic potential for the treatment of acne infection and other P. acnes related diseases.

Formulation study on retinoic acid gel composed of iota-carrageenan, polyethylene oxide and Emulgen® 408

In the present study, all-trans retinoic acid (RA) gels formulated with various compositions of polyethylene oxide (Emulgen®) and iota-carrageenan (ι-CG) were prepared and their physicochemical properties were evaluated. The compression energy, which is the work required to compress the product through a fixed distance, increased with increasing amount of ι-CG or Emulgen®. The adhesion energy and displacement decreased with increasing amount of ι-CG or Emulgen® due to the progression of gel formation. From the results of the sensory tests, the properties of RA gels such as adhesiveness, gel strength and spreadability seemed to be adjustable depending on the condition of skin by varying the components of RA gels. Through photostability study, the expiration date and storage conditions of RA gels were determined as "4°C for 28 d with no exposure to light."

Making the case for early treatment of acne

Early acne can be defined as the occurrence of acne at its onset, primarily in preteens, or as acne at its earliest severity (ie, mild to moderate). Although the majority of patients with acne are treated by dermatologists, most, particularly mild to moderate cases, could be successfully managed by primary care physicians. Therefore, it is important for physicians to understand the benefits of treating all types of acne, not just the most severe. Awareness of the emotional impact of acne, particularly in adolescence, as well as recognition of possible scarring are important considerations. To achieve optimal results, physicians should be familiar with classification and severity grading of acne. Also, in-depth knowledge of available acne medications will streamline and optimize treatment regimens. Recognizing, treating, and monitoring the progress of early acne may lead to quicker, better clinical outcomes and improved quality of life.

Tolerability of high-dose topical tretinoin: the Veterans Affairs Topical Tretinoin Chemoprevention Trial

BACKGROUND

Topical tretinoin is a medication commonly used for acne that has potential application in the long-term treatment of photodamaged skin. However, there are few published data regarding the tolerability of high-dose tretinoin with long-term use.

OBJECTIVES

To assess the long-term tolerability of tretinoin 0.1% cream.

METHODS

A randomized, multicentre, double-blind, controlled trial for chemoprevention of keratinocyte carcinomas (i.e. basal cell or squamous cell carcinomas) using topical tretinoin cream to the face and ears was conducted. All participants were veterans and had a history of two or more keratinocyte carcinomas over the previous 5 years. Participants were examined (by a study dermatologist) and interviewed every 6 months (for up to 5.5 years to May 2004). Treatment comprised tretinoin 0.1% cream or vehicle control cream once daily, then twice daily as tolerated. Participants were instructed to step down application frequency to once daily or less if twice daily was not tolerated. The main outcome measures were reported side-effects, frequency of cream application and attendance at study visits. Appropriate data were available for four of the six clinical sites of this trial.

RESULTS

Data from 736 randomized participants (mean age 71 years; 97% men) from four clinical sites were analysed. The tretinoin group more commonly reported one or more side-effects at the 6-month follow-up than the control group (61% vs. 42%, P < 0.0001). Side-effects decreased over time in both groups, but to a greater extent in the tretinoin group, and the difference became nonsignificant at 30 months. Burning was the most common side-effect (39% tretinoin vs. 17% control, P < 0.0001). There was no difference in severity of side-effects among those affected. Of the participants who reported burning in either group, most reported mild burning; only 11% of those with burning in the tretinoin group reported it as severe (mild 62% tretinoin vs. 70% placebo; severe 11% vs. 5%; P = 0.4). Itching (24% vs. 16%, P = 0.01) and other local cutaneous reactions (12% vs. 6%, P = 0.01) were also more commonly reported by the tretinoin group at 6 months. There was no difference in numbness (2% vs. 2%, P = 0.9). Participants in the tretinoin group were less likely to apply cream twice daily at 6 months (29% vs. 43%, P = 0.0002). This difference persisted over the entire duration of follow-up. There was little difference between groups in attendance at study visits or completion of telephone interviews (92% vs. 95%, P = 0.06). No unexpected adverse events were reported.

CONCLUSIONS

Overall, the tolerability level of topical tretinoin was high in this study population, with almost 40% of the tretinoin group reporting no side-effects, and the majority (67%) tolerating at least once-daily dosing at 6-month follow-up. High-dose topical tretinoin is feasible for long-term use in this population.

Topical retinoids in acne vulgaris: update on efficacy and safety

Topical retinoids represent a mainstay of acne treatment because they expel mature comedones, reduce microcomedone formation, and exert anti-inflammatory effects. The first-generation retinoid tretinoin (all-trans retinoic acid) and the synthetic third-generation polyaromatics adapalene and tazarotene are approved for acne treatment by the US FDA, whereas topical tretinoin, isotretinoin (13-cis retinoic acid), and adapalene are accredited in Canada and Europe. Topical retinoids have a favorable safety profile distinct from the toxicity of their systemic counterparts. Local adverse effects, including erythema, dryness, itching, and stinging, occur frequently during the early treatment phase. Their impact varies with the vehicle formation, skin type, frequency and mode of application, use of moisturizers, and environmental factors such as sun exposure or temperature. The broad anti-acne activity and safety profile of topical retinoids justifies their use as first-line treatment in most types of non-inflammatory and inflammatory acne. They are also suitable as long-term medications, with no risk of inducing bacterial resistance, for maintenance of remission after cessation of initial combination therapy.

A review of adapalene in the treatment of acne vulgaris

Topical retinoids help address the early lesions of acne vulgaris. Consensus guidelines advocate the use of topical retinoids as the primary treatment for most forms of acne vulgaris. However, all topical retinoid preparations may be irritating, and this may contribute to underutilization in clinical practices. Topical adapalene fosters topical retinoid treatment of acne with less irritation. Adapalene is a more stable molecule than tretinoin. Adapalene can be used without concern for photo-deactivation. Because of its chemical stability, adapalene can be used in combination with benzoyl peroxide products. The availability of a stable topical retinoid associated with little irritation may facilitate meeting acne treatment consensus guidelines.

Update in retinoid therapy of acne

The pathogenesis of acne, the most common skin disease, is complex and multifactorial. Clinical experience has demonstrated that parallel targeting of various pathogenetic factors, achieved either by mono- or combination therapy with appropriate drugs, represents the most effective approach to treating acne. Topical retinoids have been shown to expulse mature comedones, reduce microcomedone formation, and exert immunomodulatory effects. They have broad anti-acne activity without the risk of inducing bacterial resistance, which justifies their use as first-line treatment in most types of noninflammatory and inflammatory acne and makes them uniquely suitable as long-term medication to maintain remission after cessation of initial combination therapy. Systemic isotretinoin as a monotherapeutic agent strongly affects all four major pathogenetic factors and has been, in the hand of experienced dermatologists, a potent and safe agent for the treatment of severe and recalcitrant acne forms for more that 20 years. However, patient counseling, careful monitoring, and evaluation and management of adverse events are necessary. The use of isotretinoin has experienced a drawback now that its indication has been lowered from a first-line to a second-line medication.

Anti-inflammatory effects of tretinoin (all-trans-retinoic acid) 0.1% and adapalene 0.1% in rats

In this study, the anti-inflammatory effects of tretinoin (all-trans-retinoic acid) 0.1% cream and adapalene 0.1% gel were compared in rats to determine whether there was a difference between these agents. Thirty-six rats of either sex were divided into six groups (two control groups, and an etodolac, indomethacin, tretinoin and adapalene group) of six animals each. Each group was given different drugs or chemicals. The inhibitory activities of the drugs were determined on carrageenan-induced rat-paw oedema. The inhibition rate (53.48%) in the tretinoin group was found to be higher than adapalene and controls (P < 0.05). Adapalene was found to have an inhibition rate of 10.28%, and when compared with the other groups, was found to have no statistically significant anti-inflammatory activity. We conclude that tretinoin has a higher anti-inflammatory activity than adapalene and thus should be preferred for the treatment of inflammatory lesions.

Development of tretinoin gels for enhanced transdermal delivery

To develop the new gel formulations that show sustained release for a period of time, the bioadhesive carbopol gels containing tretinoin were prepared. The release characteristics of drug from the carbopol gel were studied according to temperature, receptor medium and drug concentration. For the enhancement of its percutaneous absorption, some kinds of penetration enhancer were used. As the concentration of drug increased, the release of drug from the gel increased, showing concentration dependency. The increase of temperature showed the increased drug release, depending on the activation energy of permeation. Among the enhancers used such as the glycols and the non-ionic surfactants, polyoxyethylene 2-oleyl ether showed the best enhancing effect. The carbopol gels of tretinoin containing an enhancer could be developed for the enhanced transdermal delivery of drug.

Comparison of topical retinoids in the treatment of acne

Topical retinoids are been used to successfully treat acne for almost 3 decades. At the beginning, a retinoid was a compound of similar structure and action to retinol (vitamin A).(1) Changes at the carboxylic end group, the polyene chain, and the aromatic ring can result in the modification of the original molecule. To date, three generations of retinoids have been developed: the nonaromatics (retinol, tretinoin, and isotretinoin), the monoaromatics (etretinate and acitretin), and the polyaromatics (arotinoid, adapalene, and tazarotene). The new synthetic retinoid molecules have little resemblance with retinol but nonetheless are included in this family because they have the ability to bind with or activate retinoid receptors. Therefore, retinoids are vitamins and also hormones.(3)

Adapalene

Adapalene (Differin) is a retinoid agent indicated for the topical treatment of acne vulgaris. In clinical trials, 0.1% adapalene gel has proved to be effective in this indication and was as effective as 0.025% tretinoin gel, 0.1% tretinoin microsphere gel, 0.05% tretinoin cream and 0.1% tazarotene gel once every two days; however, the drug was less effective than once-daily 0.1% tazarotene gel. It can be used alone in mild acne or in combination with antimicrobials in inflammatory acne and has proved efficacious as maintenance treatment. Adapalene has a rapid onset of action and a particularly favourable tolerability profile compared with other retinoids. These attributes can potentially promote patient compliance, an important factor in treatment success. Adapalene is, therefore, assured of a role in the first-line treatment of acne vulgaris.

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.

Retinoids: fascinating up-and-coming scenario

Retinoids have been in sharp focus ever since their introduction 30 years ago. They include any drug (s) that bind to retinoid receptors and elicit a biological response. Enormous information on the subject seems to embroil the recent literature. Practically it is impossible to clearly comprehend the undercurrents. The meticulously dispensing text envisages surmounting the perspective reader's predicaments. Accordingly, retinoids and their related facets namely retinoid receptors, classification, mode of action, and the pharmacological diversity have been precisely defined. Commonly used systemic retinoids too have been given a substantial fresh look along with their monitoring. Overall, adverse effects and relative and absolute contraindications have been scrupulously incorporated. Human immuno deficiency virus (HIV) and isoretinoid for acne, in particular, have been highlighted. Micronized isotretinoin formulations have also been taken care so also commonly used topical retinoids. Tretinoin and their newer formulation have also been accounted for along with tretinoin polymer cream. Adapalene, a new chemical entity possessing a unique physico-chemical activity similar to that of tretinoin has also been dealt with. Newer retinoids are likely to be a subject of intrigue. A focus on future potentials of retinoids is its special ingredient. The inclusion of details of rexinoid the most recent introduction in their purview is likely to invoke interest to further consolidate its reckoning in future. All in all the text of the paper should provide an insight into the current rumbling around retinoids.