Stability of topical erythromycin formulations

Low-dose erythromycin in pediatrics: Formulation and stability of 20 mg hard gelatin capsules

OBJECTIVE

Erythromycin is a macrolide antibiotic that is also prescribed off-label in premature neonates as a prokinetic agent. There is no oral formulation with dosage and/or excipients adapted for these high-risk patients.

METHODS

Clinical studies of erythromycin as a prokinetic agent were reviewed. Capsules of 20 milligrams of erythromycin were compounded with microcrystalline cellulose. Erythromycin capsules were analyzed using the chromatographic method described in the United States Pharmacopoeia which was found to be stability-indicating. The stability of 20 mg erythromycin capsules stored protected from light at room temperature was studied for one year.

RESULTS

20 mg erythromycin capsules have a beyond use date not lower than one year.

CONCLUSION

20 milligrams erythromycin capsules can be compounded in batches of 300 unities in hospital pharmacy with a beyond-use-date of one year at ambient temperature protected from light.

Erythromycin Formulations—A Journey to Advanced Drug Delivery

Erythromycin (ERY) is a macrolide compound with a broad antimicrobial spectrum which is currently being used to treat a large number of bacterial infections affecting the skin, respiratory tract, intestines, bones and other systems, proving great value from a clinical point of view. It became popular immediately after its discovery in 1952, due to its therapeutic effect against pathogens resistant to other drugs. Despite this major advantage, ERY exhibits several drawbacks, raising serious clinical challenges. Among them, the very low solubility in water and instability under acidic conditions cause a limited efficacy and bioavailability. Apart from this, higher doses promote drug resistance and undesirable effects. In order to overcome these disadvantages, during the past decades, a large variety of ERY formulations, including nanoparticles, have emerged. Despite the interest in ERY-(nano)formulations, a review on them is lacking. Therefore, this work was aimed at reviewing all efforts made to encapsulate ERY in formulations of various chemical compositions, sizes and morphologies. In addition, their preparation/synthesis, physico-chemical properties and performances were carefully analysed. Limitations of these studies, particularly the quantification of ERY, are discussed as well.

The Effect of Cationic Polyamidoamine Dendrimers on Physicochemical Characteristics of Hydrogels with Erythromycin

Polyamidoamine dendrimers (PAMAM) represent a new class of hyperbranched, monodisperse, three-dimensional polymers with unique properties, which make them very promising carriers of antimicrobial agents. The present study aimed to evaluate the influence of PAMAM-NH₂ dendrimers generation two (G2) or three (G3) on physicochemical characteristics and structure of hydrogels with a model antibacterial lipophilic drug-erythromycin-commonly used in topical applications. From the obtained rheograms, it can be concluded that tested hydrogels were non-Newtonian thixotropic systems with shear-thinning behaviour. The dissolution tests revealed that erythromycin was definitely faster released from formulations containing PAMAM-NH₂ in concentration and generation dependent manner. However, the addition of PAMAM-NH₂ to hydrogels evoked only slight improvement of their antibacterial activity. It was also shown that the structure of hydrogels changed in the presence of PAMAM-NH₂ becoming less compact, diversified and more porous. Designed hydrogels with PAMAM-NH₂ G2 or G3 were stable stored up to three months at 40 ± 2 °C and 75% ± 5% RH.

Development of Novel Nonaqueous Ethylcellulose Gel Matrices: Rheological and Mechanical Characterization

PURPOSE

This study reports the rheological and mechanical characterization of novel non-aqueous ethylcellulose gel matrices intended for topical drug delivery. An attempt was also made to explain the molecular interaction within the gel systems from a molecular conformational approach.

METHODS

Nonaqueous gel matrices were prepared from three fine particle grades of ethylcellulose and propylene glycol dicaprylate/dicaprate. Continuous and oscillatory shear rheometry was performed using a cone-and-plate rheometer and mechanical characterization was performed using a universal tensile tester.

RESULTS

The gel matrices exhibited prominent viscoelastic behaviour, yield stress and thixotropy. Rheological and mechanical properties showed significant upward trends with increased polymeric chain length and polymer concentrations. Good linear correlations were obtained between rheological and mechanical properties. The solvent molecular conformation was found to play a role in affecting the formation of gel networks via intermolecular hydrogen bonding between ethylcellulose polymer chains.

CONCLUSIONS

Ethylcellulose was successfully formulated as a nonaqueous gel with propylene glycol dicaprylate/dicaprate. The novel nonaqueous gel exhibited rheological profiles corresponding to a physically cross-linked three dimensional gel network, with suitable mechanical characteristics for use as a vehicle for topical drug delivery. Molecular conformation of the solvent was found to influence the molecular interactions associated with formation of ethylcellulose gel networks.

Investigation of the chemical stability of an erythromycin-tretinoin lotion by the use of an optimization system

A combination of 2% erythromycin and 0.05% tretinoin in an alcohol-isopropanol lotion was prepared. Two parameters were investigated for their influence on the stability of erythromycin and/or tretinoin, namely pH and the concentration of butylhydroxytoluene (BHT) as antioxidant. To investigate these two parameters, an optimization technique was used with two factors (pH and concentration of BHT) at two levels. Accelerated stability analysis was performed at 45 degrees C in the dark to exclude isomerization of tretinoin. To analyse erythromycin and tretinoin in the combination preparation, a TLC method, previously developed in the laboratory, was used. The degradation of erythromycin seemed to be much faster than the tretinoin degradation. Optimal stability is shown in the pH range of 8.2-8.6 for erythromycin and 7.2-8.2 for tretinoin while the concentration of BHT had no significant influence.

The formulation and stability of erythromycin-benzoyl peroxide in a topical gel

The combination of benzoyl peroxide and erythromycin is used for the local treatment of acne and available as a commercial preparation. Because of the stability problems of erythromycin an extempore preparation is required. The influence of storage temperature and non active ingredients on the stability of benzoyl peroxide and erythromycin in topical gel preparations for extempore compounding is described. A microbiological and an HPLC method were used to determine the erythromycin and the benzoyl peroxide concentrations, respectively. For a formulation compounded with hydroxyethylcellulose no stability problems were observed. For the formulation containing Carbopol 940, the levels of erythromycin varied over a wide range due to precipitation and aggregation of the drug during compounding.