Evaluation of skin permeation of β-blockers for topical drug delivery

Exploring the Antibacterial Potential of Semisynthetic Phytocannabinoid: Tetrahydrocannabidiol (THCBD) as a Potential Antibacterial Agent against Sensitive and Resistant Strains of Staphylococcus aureus

Antimicrobial resistance (AMR) is one of the most challenging problems and is responsible for millions of deaths every year. We therefore urgently require new chemical entities with novel mechanisms of action. Phytocannabinoids have been adequately reported for the antimicrobial effect but not seriously pursued because of either stringent regulatory issues or poor drug-like properties. In this regard, the current work demonstrated the antibacterial potential of tetrahydrocannabidiol (THCBD, 4), a semisynthetic phytocannabinoid, against Staphylococcus aureus, the second-most widespread bug recognized by the WHO. THCBD (4) was generated from cannabidiol and subjected to extensive antibacterial screening. In in vitro studies, THCBD (4) demonstrated a potent MIC of 0.25 μg/mL against Gram-positive bacteria, S. aureus ATCC-29213. It is interesting to note that THCBD (4) has demonstrated strong effectiveness against efflux pump-overexpressing (SA-1199B, SA-K2191, SA-K2192, and Mupr-1) and multidrug-resistant (MRSA-15187) S. aureus strains. THCBD (4) has also shown a good effect in kill kinetic assays against ATCC-29213 and MRSA-15187. In the checkerboard assay, THCBD (4) has shown additive/indifference effects with several well-known clinically used antibiotics, tetracycline, mupirocin, penicillin G, and ciprofloxacin. THCBD (4) also exhibited good permeability in the artificial skin model. Most importantly, THCBD (4) has significantly reduced CFU in mice's in vivo skin infection models and also demonstrated decent plasma exposure with 16-17% oral bioavailability. Acute dermal toxicity of THCBD (4) suggests no marked treatment-related impact on gross pathophysiology. This attractive in vitro and in vivo profile of plant-based compounds opens a new direction for new-generation antibiotics and warrants further detailed investigation.

Modeling the percutaneous absorption of solvent-deposited solids over a wide dose range: II. Weak electrolytes

Dermal absorption of weak electrolytes applied to skin from pharmaceutical and cosmetic compositions is an important consideration for both their efficacy and skin safety. We developed a mechanistic, physics-based framework that simulates this process for leave on applications following solvent deposition. We incorporated this framework into our finite dose computational skin permeation model previously tested with nonelectrolytes to generate quantitative predictions for weak electrolytes. To test the model, we analyzed experimental data from an in vitro human skin permeation study of a weak acid (benzoic acid) and a weak base (propranolol) and their sodium and hydrochloride salts from simple, ethanol/water vehicles as a function of dose and ionization state. Key factors controlling absorption are the pH and buffer capacity of the dose solution, the dissolution rate of precipitated solids into a lipid boundary layer and the rate of conversion of the deposited solid to its conjugate form as the nonionized component permeates and (sometimes) evaporates from the skin surface. The resulting framework not only describes the current test data but has the potential to predict the absorption of other weak electrolytes following topical application.

Lateral Transport During Membrane Permeation in Diffusion Cell: In Silico Study on Edge Effect and Membrane Blocking

Membrane transport in diffusion cell studies is not one-dimensional from the donor to the receptor. Lateral diffusion within the membrane into the surrounding clamped region can lead to edge effect. Lateral diffusion can also affect the impact of an object blocking the membrane in a diffusion cell. The effects of lateral transport on permeation across a two-layer membrane in diffusion cells were investigated in this study under edge effect and membrane blocking conditions that could be encountered in previous gingiva and hypothetical skin permeation studies. Model simulations of time-dependent and steady-state transport were performed using COMSOL Multiphysics. The simulations indicated edge effect could increase the steady-state flux across the membrane up to 35% with a relatively thick membrane and small diffusion cell opening (e.g., gingiva study). The edge effect decreased when the relative thickness and permeability of the major barrier (top layer in the two-layer membrane) decreased. When the membrane was partially blocked by an object, lateral diffusion within the membrane could mitigate its impact: e.g., when the object was in the receptor, the impact caused by membrane blocking was reduced more than half. Therefore, membrane lateral transport should be considered under certain circumstances in permeation studies using diffusion cells.

Application of topical betaxolol to cure superficial infantile hemangioma: A pilot study

BACKGROUND

Beta-blockers have gradually become an attractive option for the treatment of infantile hemangiomas. Topical application is preferred to oral administration because of their potential systemic adverse effects. The aim of this study is to investigate the effect of betaxolol in treating superficial infantile hemangioma.

METHODS

Seventy-four infants admitted to the First Affiliated Hospital of Xinjiang Medical University from 2018 to 2019 were observed and recorded. Variables such as color, size, tension, and thickness were recorded monthly and evaluated using visual analog scales. Multi-factor analysis of variance with repeated measurements and the non-parametric Kruskal-Wallis H test were used to compare clinical effectiveness across the different groups.

RESULTS

After 6 months of treatment, 33.78% (25/74) showed excellent results, 55.41% (41/74) had good responses, 8.11% (6/74) had moderate responses, and 2.70% (2/74) had poor responses. Local discomfort and systemic complications were not found. There was no significant difference in gender and location of occurrence among groups (p > 0.05), and the effect of topical application of betaxolol was optimum in the children aged 0-3 months (p = 0.002). None of three age groups had statistically significant difference in heart rate and blood pressure after accepting treatment (1 month, p = 0.618; 4 months, p = 0.138; 6 months, p = 0.757).

CONCLUSIONS

Our study showed that topical administration of betaxolol was effective and well tolerated for superficial infantile hemangiomas, particularly in the early proliferative stage. However, its safety and efficacy need further research.

An infant with localized vasoconstriction following topical propranolol exposure for infantile hemangioma

We describe a 3-month-old child with an infantile hemangioma on the forehead with a blanched macule provoked by topical treatment with propranolol. This observation demonstrates that topically applied (non-selective) beta-blockers may induce blanched macules at the site of application, a side effect due to peripheral vasoconstriction of blood vessels by non-selective beta-2 blockade. This side effect was linked due to overuse and was reversible. This case illustrates the importance of providing thorough instructions regarding topical propranolol application.

Using Esterase Selectivity to Determine the In Vivo Duration of Systemic Availability and Abolish Systemic Side Effects of Topical β-Blockers

For disorders of the skin, eyes, ears, and respiratory tract, topical drugs, delivered directly to the target organ, are a therapeutic option. Compared with systemic oral therapy, the benefits of topical treatments include a faster onset of action, circumventing the liver first pass drug metabolism, and reducing systemic side effects. Nevertheless, some systemic absorption still occurs for many topical agents resulting in systemic side effects. One way to prevent these would be to develop drugs that are instantly degraded upon entry into the bloodstream by serum esterases. Because topical β-blockers are used in glaucoma and infantile hemeangioma and cause systemic side effects, the β-adrenoceptor system was used to test this hypothesis. Purified liver esterase reduced the apparent affinity of esmolol, an ester-containing β-blocker used in clinical emergencies, for the human β-adrenoceptors in a concentration and time-dependent manner. However, purified serum esterase had no effect on esmolol. Novel ester-containing β-blockers were synthesized and several were sensitive to both liver and serum esterases. Despite good in vitro affinity, one such compound, methyl 2-(3-chloro-4-(3-((2-(3-(3-chlorophenyl)ureido)ethyl)amino)-2-hydroxypropoxy)phenyl)acetate, had no effect on heart rate when injected intravenously into rats, even at 10 times the equipotent dose of esmolol and betaxolol that caused short and sustained reductions in heart rate, respectively. Thus, ester-based drugs, sensitive to serum esterases, offer a mechanism for developing topical agents that are truly devoid of systemic side effects. Furthermore, differential susceptibility to liver and serum esterases degradation may also allow the duration of systemic availability for other drugs to be fine-tuned.

Sclerotherapy and Topical Nasal Propranolol: An Effective and Safe Therapy for HHT-Epistaxis

OBJECTIVES

Epistaxis is the most frequent clinical manifestation of hereditary hemorrhagic telangiectasia (HHT). Several topical, systemic, and surgical treatments have been tried, but none have been completely effective. The aim of the present study is to evaluate whether a combined treatment sclerotherapy and topical therapy with propranolol 0.5% nasal formulation would reduce the epistaxis due to HHT and improve patient's quality of life.

METHODS

An observational cross-sectional study was carried out. The primary outcome measure was frequency and severity of epistaxis as measured by the epistaxis severity score (ESS) at baseline (4 weeks before therapy) and at least 4 weeks after the treatment was implemented. Quality of life was analyzed using EuroQol-5D (EQ-5D) scale and visual analogue (VAS) scale before and after treatment.

RESULTS

A total of 38 consecutive patients subjected to the combined treatment were evaluated (mean age: 57.2 years, standard deviation [SD] = 13.9; 60.5% women). The mean time of treatment was 37.1 weeks (SD = 14.9). Combined therapy significantly reduces frequency and severity of epistaxis, with an ESS improvement of 5 points from 6.9 ± 2.6 to 1.9 ± 1.3 (P < 0.05); however, the EQ-5D scale increased from 0.66 ± 0.27 to 0.93 ± 0.12 (P < 0.05). The difference in VAS means showed an increase from 44.6 ± 28.3 to 82.5 ± 12.5 (P < 0.05). The increases in quality of life are in line with the drop in ESS.

CONCLUSION

The study demonstrated that combined therapy (sclerotherapy and topical nasal propranolol) significantly reduced the epistaxis due to HHT and increased patients' quality of life.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:2216-2223, 2019.

The Influence of Formulation and Excipients on Propranolol Skin Permeation and Retention

The objective of this work was to study in vitro propranolol permeation and skin retention after topical application of different semisolid vehicles, with the final aim of developing new topical formulations intended for the treatment of infantile hemangioma, able to produce therapeutic drug levels in the skin, avoiding systemic absorption. Propranolol ointments, creams, and gels were prepared and tested on pig skin, an accepted model of human skin. From the results obtained in the present work it is clear that the permeation of propranolol across the skin is a poor predictor of its skin retention, at least in the time-frame considered. With an application time of 4 h, reasonably close to the permanence time of a semisolid formulation on the skin surface, the best performance (high retention and low skin penetration) was obtained with lipophilic formulations, in particular with a lipophilic cream containing olive oil. Hydrophilic formulations, such as gels, are characterized by a significant permeation across the skin, probably leading to systemic side effects, accompanied by a limited skin retention. Overall, the results obtained in the present work pose the basis for the development of new topical formulations, containing propranolol, with better performance and reduced systemic absorption.

Topical propranolol for infantile haemangiomas: a systematic review

Infantile haemangiomas are the most common tumour of infancy. Whilst the majority are left untreated to involute spontaneously, residual skin changes commonly occur, particularly in superficial haemangiomas. The current first-line treatment for problematic lesions is oral propranolol; however due to the risk of systemic adverse effects, the use of off-label topical preparations has recently been investigated. Our systematic review was conducted in accordance with PRISMA guidelines. Four databases were searched to identify original articles evaluating the use of topical propranolol as the primary therapy for infantile haemangiomas. Twelve articles with a total of 597 patients and 632 haemangiomas were included. Three topical propranolol preparations were used, creams, ointments and gels and were all prepared by local pharmaceutical laboratories. The concentration of propranolol ranged from 0.5% to 5%. Treatment duration ranged from two weeks to 16.5 months. Overall, 90% of lesions improved following the initiation of topical propranolol. A good or excellent response, defined as a reduction in the size of at least 50%, was seen in 59% of lesions. Earlier initiation of treatment (less than 3 months of age) was associated with improved outcomes. No systemic adverse effects were reported. Minor local reactions were seen in 1.3% of patients. Topical propranolol is safer than oral propranolol, though may be less effective. Topical propranolol may be more suitable for patients with small, superficial haemangiomas at risk of cosmetic sequelae, where the cosmetic or symptomatic impact does not warrant oral propranolol treatment.

Topical Timolol Maleate Treatment of Infantile Hemangiomas

BACKGROUND

There has been a dramatic increase in the off-label use of ophthalmic timolol maleate, a β-blocker used for infantile hemangioma (IH) treatment as a topical counterpart to oral propranolol. Its safety and efficacy in a pediatric population with IH have not been evaluated in a large cohort. Our goal was to retrospectively assess timolol's effectiveness, discern characteristics associated with response, and document reported adverse events.

METHODS

A multicenter retrospective cohort study of 731 patients treated with topical timolol was completed at 9 centers. Inclusion required an IH suitable for timolol in the treating physician's judgment and access to clinical details including photographs. Logistic regression analysis and descriptive statistics were performed. Primary outcome measures were efficacy assessed by using visual analog scales for color and for size, extent, and volume from review of digital photographs taken as standard of care.

RESULTS

Most IHs were localized (80.1%) and superficial (55.3%). Risk of disfigurement was the most common indication for therapy (74.3%). Duration of therapy (P < .0001), initial thinness (P = .008), and subtype (P = .031) were significant predictors of response. Best response occurred in superficial IHs <1 mm thick. Fifty-three (7.3%) required subsequent therapy with systemic β-blocker. Adverse events were mild, occurring in 25 (3.4%) patients. No cardiovascular side effects were documented.

CONCLUSIONS

Timolol seems to be a well-tolerated, safe treatment option with moderate to good effectiveness, demonstrating best response in thin, superficial IHs regardless of pretreatment size. Timolol can be recommended as an alternative to systemic β-blockers and watchful waiting for many patients.

Methylation and Esterification of Magnolol for Ameliorating Cutaneous Targeting and Therapeutic Index by Topical Application

PURPOSE

As a continuing effort to elucidate the impact of structure modification upon cutaneous absorption behavior, we attempted to assess the skin permeation of magnolol by methylation and acetylation.

METHODS

Diacetylmagnolol and 2-O-acetyl-2'-O-methylmagnolol (AMM) were designed and synthesized in this study. The anti-inflammatory activity against stimulated neutrophils and keratinocytes was evaluated to check the bioactivity of the analogues. In vitro skin absorption was investigated using nude mouse and pig skin models at both equimolar and saturated doses.

RESULTS

Magnolol generally showed the strongest anti-inflammatory potential, followed by diacetylmagnolol and AMM. The antibacterial activity was observed for magnolol and diacetylmagnolol but not AMM. Diacetylmagnolol and AMM could be partly hydrolyzed to magnolol and 2-O-methylmagnolol after entering the skin. The hydrolysis rate of diacetylmagnolol was faster than that of AMM. The lipophilicity played a crucial role in cutaneous absorption, with AMM exhibiting the highest skin deposition. AMM accumulation within nude mouse skin was about 2.5-fold greater than that of magnolol and diacetylmagnolol. On the other hand, the transdermal penetration across the skin was lessened by methylation and esterification. This led to a superior skin targeting of AMM. Although the pharmacological activity of AMM was low, the high skin uptake and bioconversion into 2-O-methylmagnolol in the skin contributed to a greater therapeutic index (TI, skin deposition x inflammatory inhibition percentage) compared to the others. The accumulation of AMM in the hair follicles was 77.12 nmol/cm(2), which was significantly greater than that with magnolol (44.84 nmol/cm(2)) and diacetylmagnolol (26.96 nmol/cm(2)). The synthetic analogues were tolerable to the nude mouse skin.

CONCLUSIONS

Based on the experimental results, we may suggest topically applied AMM as a potent and safe candidate for the treatment of cutaneous inflammation.

Educational paper: therapy of infantile haemangioma--history and current state (part II)

Infantile haemangioma (IH) is the most frequent tumour of infancy. Although it is benign and self-limiting, severe complications can arise due to localisation and fast tumour growth. Also, IHs leave scars after regression in more than half of the cases. Management and therapy of IH have changed greatly after 2008. This update provides an overview of the older therapy options before 2008, which mainly consisted of the administration of corticosteroids, and discusses the modern management with new therapy options such as β-blockers (both systemically and topically).

CONCLUSION

β-blockers are promising and are currently preferred above corticosteroids, but β-blockers still do not give a definitive treatment.

Topical treatment with propranolol gel as a supplement to the existing treatment of hemangiomas

BACKGROUND

Systemic treatment with propranolol is proven to be effective for patients with hemangiomas with less side-effect. We used a propranolol gel for topical use on hemangiomas.

METHODS

In this retrospective study, we analyzed 148 patients who had been treated topically with propranolol gel for 12 weeks. We analyzed the data of patients and clinically gave each hemangioma a "hemangioma score" to determine the treatment success.

RESULTS

In 147 of the 148 patients, strong signs of resolution under treatment included lightening, paling, and less vascularization. The hemangioma score showed a significant decrease during the treatment. Relevant serum levels of propranolol were not found. Adverse effects were rare and not related to propranolol.

CONCLUSION

Topical treatment with propranolol gel is suitable for specific hemangiomas in addition to cryotherapy and systemic treatment with propranolol.

[Rapid regression of infantile haemangioma with 2% propranolol ointment]

BACKGROUND

Oral propranolol produces dramatic results in severe infantile haemangioma. We report a case of rapid and significant regression of an infantile haemangioma in infant treated topically with 2% propranolol ointment.

PATIENTS AND METHODS

A female infant aged 11 weeks was seen as an outpatient for two infantile haemangiomas on the front of the left knee and the vulva. After parental consent was given, the child was treated with a topical preparation of 2% propranolol ointment prepared by the pharmacy. Regression was rapid and on the 45th day, lesion size had been reduced by an estimated 75%. No adverse effects were observed.

DISCUSSION

Topical propranolol appears to be effective and safe for the treatment of superficial haemangiomas. Clinical trials are required to determine the optimal dosage and pharmaceutical form, method of use and treatment duration.