Percutaneous absorption of sodium fusidate and fusidic acid

Topical antibiotics in pregnancy: A review of safety profiles

Medications should be used with caution in women of childbearing age who are pregnant, or are contemplating pregnancy. Although topical medications are considered safer than oral or parenteral agents, their safety data in pregnancy must be assessed carefully. The available information on medication use in pregnancy is limited, and not always aided by the FDA pregnancy letter category system. Thus, in this article, we aggregate human studies, animal studies, and pharmacokinetics data to provide recommendations on utilizing topical antibiotics in pregnancy.

Drug crystallization - implications for topical and transdermal delivery

INTRODUCTION

Crystallization of actives in skin following topical application was suggested by studies in the 1950s and 1960s but is poorly understood. In contrast, the problem of crystallization of actives on skin and in transdermal formulations has been known for many years.

AREAS COVERED

With respect to crystallization in skin, this review describes early reports of a skin 'reservoir' and possible reasons underlying its genesis. Techniques to study crystallization on and in skin and in transdermal patches are outlined. The role of the vehicle in skin delivery is emphasised. Studies which have investigated permeation from crystalline particles are described. Approaches to limit crystallization of actives are discussed. Using supersaturation and antinuclean polymers, control of crystal size is possible; controlled release from crystals is also employed in transdermal patches.

EXPERT OPINION

Drug crystallization has significant implications for topical and transdermal delivery. Approaches have been developed to counteract the issue for transdermal patches but crystallization in and on the skin for other formulations remains unresolved. Greater knowledge of residence time of excipients and their interaction with skin at the molecular level is critical in order to address the problem. This will lay the foundations for better design of topical/transdermal formulations.

Topische Antibiotika zur Therapie von Hautinfektionen

To understand the development of bacterial resistance and multi-resistance following treatment with topical and systemic antibiotics is important for dermatologists. Furthermore the sensitization potential and toxicity of antibiotics applied to large skin areas must be considered. The advantage of many topical antibiotics is evident; extremely high concentrations can be achieved in the infected skin usually without any systemic side effects. When an antibiotic is used both systemically and topically, indications should be weighed carefully for topical use, in order to reduce the likelihood of sensitization to an potential systemic agent. Continuous monitoring of the resistance profile of important bacteria is also desirable, in order to preserve the utility of important "reserve antibiotics". In this review the most important topical antibiotics used in Germany are evaluated with regards to efficacy and safety profile.

In vitro percutaneous absorption of fusidic acid and betamethasone 17-valerate across canine skin

The penetration of betamethasone 17-valerate and fusidic acid through dog skin was measured in vitro. In order to detect the small amounts of diffused compounds, a liquid chromatography-mass spectrometric method was developed with sensitivity limits for both compounds of 5 ng/ml. After application to the skin surface of a topical gel preparation containing these compounds at the anticipated therapeutic dose rate, about 10 per cent of the betamethasone 17-valerate penetrated the skin over a 24-hour period, with no significant metabolism of the ester. About 1.3 per cent of the applied dose of fusidic acid was similarly recovered. The results demonstrated rapid penetration of both compounds through the epidermis.

Fusidic acid pharmacology, pharmacokinetics and pharmacodynamics

Fusidic acid comes in a variety of formulations for oral, intravenous and topical use. After oral administration of 500 mg Cmax values range from 14.5-3.3 mg/l and an elimination half-life of 8.9-11.0 h. Similar values are obtained with intravenous administration of the sodium salt, although peaks tend to be higher. Bioavailability for the new film-coated tablet is approximately 91% while that of the suspension formulation appears to be much lower. Repeated dosing results in substantial drug accumulation when given 8-hourly, and to a variable extent depending on dose when administered 12-hourly. One study has demonstrated a modest dose-dependency for pharmacokinetics, with decreased clearance at higher doses. Fusidic acid is primarily eliminated by non-renal mechanisms, and a proportion of the drug is metabolised to seven or more breakdown products that can be detected in bile. Hypoalbuminaemia increases fusidic acid clearance, while clearance is decreased in the presence of severe cholestasis, and essentially unchanged in renal failure. Fusidic acid is highly protein-bound (91-98S), but has good penetration to a number of tissues including skin blisters, burns, infected bone and joints. Topical application of fusidic acid results in poor penetration through skin but good penetration into aqueous and vitreous humour. Little is known about the pharmacodynamics of fusidic acid, apart from the fact that it is slowly bactericidal against Staphylococcus aureus, and produces moderate post-antibiotic effects in vitro.

Fusidic acid in dermatology

Fusidic acid is an antibiotic that belongs to a group of its own, the fusidanes. The molecule has a steroid-like structure but does not possess any steroid activity. The structure is thought to be responsible for the steroid-like high penetration, and for the fact that no cross-resistance or cross-allergy has been seen with other antibiotics in routine clinical use. The anti-microbial activity of fusidic acid is specifically aimed at the most common skin pathogens, including Staphylococcus aureus, towards which it is one of the most potent antibiotics. The place of fusidic acid in dermatology is in the treatment of mild to moderately severe skin and soft-tissue infections, e.g. impetigo, folicullitis, erythrasma, furunculosis, abscesses and infected traumatic wounds, whereas it is of less use in conditions such as hidradenitis suppurativa, chronic leg ulcers, burns and pressure sores. The topical combinations of fusidic acid with either betamethasone or hydrocortisone are extremely useful in the treatment of atopic dermatitis/eczema whenever staphylococcal/secondary infection is suspected, and in more persistent cases of eczema where staphylococcal superantigen may be playing an important exacerbating role.

Elimination of Staphylococcus intermedius in healthy dogs by topical treatment with fusidic acid

Cutaneous and mucosal carriage of Staphylococcus intermedius was investigated in six healthy beagles before and after application of fusidic acid to mucosal surfaces as 1 per cent viscous eye drops twice daily for seven days. Bacterial populations were determined repeatedly over four weeks using quantitative techniques. The overall cutaneous populations of S intermedius reduced significantly (P < 0.001) two days after treatment but returned to pretreatment levels after a further week. The mucosal frequency of S intermedius reduced significantly (P < 0.01) two days after treatment and remained reduced (P < 0.01) at the end of the study. The mucosal populations were also reduced (P < 0.01) two days after treatment and remained lower (P < 0.05) after a further week. No such changes occurred in the control group of six beagles. The study indicates the importance of mucosae as carriage sites for S intermedius in dogs. This form of therapy may be useful as an additional tool against canine recurrent pyoderma.

Systemic or local treatment of erythrasma? A comparison between erythromycin tablets and Fucidin cream in general practice

In a Danish multi-practice study the efficacy of erythromycin tablets (Abboticin 500 mg tablets), fusidic acid cream (Fucidin cream), and placebo was compared in 86 patients (71 men and 15 women) with erythrasma. The patients were treated 'double-blind' for 14 days with either active tablets + placebo cream, placebo tablets + active cream, or placebo tablets + placebo cream. The signs of erythrasma, i.e. colour intensity, demarcation, and scaling of the affected area, as well as degree of fluorescence under Wood's light, were recorded before treatment, after one and two weeks, and at follow-up four weeks later. Cure/improvement was obtained in 77% of the cases in the erythromycin group, 87% in the fusidic acid group, and 42% in the placebo group. There was no difference between the active preparations, whereas both were significantly better than placebo, P = 0.01.

The use of N,N-diethyl-m-toluamide to enhance dermal and transdermal delivery of drugs

A dermal penetration enhancer has been found which improves the dermal delivery of a wide variety of drugs and at the same time has a history of low toxicity for human dermal application. N,N-Diethyl-m-toluamide (I) has been shown to improve the delivery of many drugs through hairless mouse skin in an in vitro diffusion cell model. A topically applied steroid, hydrocortisone, has been used to demonstrate the in vivo effectiveness of I on human skin. The degree of pallor produced on human skin by the corticosteroids was used as a measure of the relative delivery of hydrocortisone from formulations with and without I.

Comparative trial of fucidin ointment and fucidin cream in skin sepsis

A study has been conducted on 101 patients with superficial skin sepsis comparing the effectiveness of topical treatment with 2% sodium fusidate ointment and a new preparation containing 2% fusidic acid in a cream base. The results showed that both topical preparations were equally effective in terms of the number of days for healing to take place and in the subjective assessment of the clinical response. Bacteriological investigation of the swabs from ninety-one patients showed Staphylococcus aureus to be the most frequently isolated pathogen. Both preparations were well tolerated and no adverse reactions were observed. It is suggested that the new 2% fusidic acid cream is particularly suitable for use on lesions requiring no dry dressing, whereas the 2% sodium fusidate ointment is preferred for those conditions where a dressing is applied.

A comparison of sodium fusidate ointment ('Fucidin') alone versus oral antibiotic therapy in soft-tissue infections

A study was carried out in 90 patients with superficial, soft-tissue infections to compare the effectiveness of topical treatment with 2% sodium fusidate ointment used alone, and oral antibiotic therapy (clindamycin, erythromycin, or flucloxacillin) plus a placebo ointment. The results showed that the number of days for healing to take place was significantly shorter with sodium fusidate ointment, and there was also a highly significant preference for it over oral antibiotic therapy in the subjective assessment of clinical response. Bacteriological investigations of swabs from 58 of the patients showed Staphylococcus aureus to be the most frequently isolated pathogen: 72% of the strains were penicillin-resistant but all were sensitive to sodium fusidate. It is suggested that oral antibiotic therapy should be reserved for those cases where there is evidence of systemic spread of the infection and that sodium fusidate ointment, with or without surgical drainage, should be the standard initial treatment in the out-patient and general practice situation.