Pediatric Erythromycins: a Comparison of the Properties of Erythromycins A and B 2‘-Ethyl Succinates

Strategies for Taste Masking of Orodispersible Dosage Forms: Time, Concentration, and Perception

Orodispersible dosage forms, characterized as quick dissolving and swallowing without water, have recently gained great attention from the pharmaceutical industry, as these forms can satisfy the needs of children, the elderly, and patients suffering from mental illnesses. However, poor taste by thorough exposure of the drugs' dissolution in the oral cavity hinders the effectiveness of the orodispersible dosage forms. To bridge this gap, we put forward three taste-masking strategies with respect to the intensity of time, concentration, and perception. We further investigated the raw material processing, the composition of auxiliary material, formulation techniques, and process control in each strategy and drew conclusions about their effects on taste masking.

Selected Derivatives of Erythromycin B-In Silico and Anti-Malarial Studies

Erythromycin A is an established anti-bacterial agent against Gram-positive bacteria, but it is unstable to acid. This led to an evaluation of erythromycin B and its derivatives because these have improved acid stability. These compounds were investigated for their anti-malarial activities, by their in silico molecular docking into segments of the exit tunnel of the apicoplast ribosome from Plasmodium falciparum. This is believed to be the target of the erythromycin A derivative, azithromycin, which has mild anti-malarial activity. The erythromycin B derivatives were evaluated on the multi-drug (chloroquine, pyrimethamine, and sulfadoxine)-resistant strain K1 of P. falciparum for asexual growth inhibition on asynchronous culture. The erythromycin B derivatives were identified as active in vitro inhibitors of asexual growth of P. falciparum with low micro-molar IC₅₀ values after a 72 h cycle. 5-Desosaminyl erythronolide B ethyl succinate showed low IC₅₀ of 68.6 µM, d-erythromycin B 86.8 µM, and erythromycin B 9-oxime 146.0 µM on the multi-drug-resistant K1 of P. falciparum. Based on the molecular docking, it seems that a small number of favourable interactions or the presence of unfavourable interactions of investigated derivatives of erythromycin B with in silico constructed segment from the exit tunnel from the apicoplast of P. falciparum is the reason for their weak in vitro anti-malarial activities.

Development and validation of a stability indicating HPLC method for organic impurities of erythromycin stearate tablets

A rapid, sensitive, and accurate high-performance liquid chromatography (HPLC) method was developed and validated for the separation and analysis of organic impurities in erythromycin stearate tablets. The method separates Erythromycin, Erythromycin B, Erythromycin C and nine impurities (EP Impurity A, B, C, D, E, F, H, I and M). The chromatographic separation was achieved on a Waters XBridge C18 (100 mm × 4.6 mm, 3.5 μm) column. The mobile phase comprised of 0.4 % ammonium hydroxide in water and methanol delivered in a gradient mode. The compounds of interest were monitored at 215 nm. The stability-indicating capability of this method was evaluated by performing stress studies. Erythromycin was found to degrade significantly under acid, base, and oxidative stress conditions and it was only stable under thermal and photolytic degradation conditions. The degradation products were well resolved from the erythromycin peaks. In addition, the major degradants formed under stress conditions were characterized by ultra-high-performance liquid chromatography coupled with Single-Quadrupole Mass Spectrometer (UHPLC-QDa). The method was validated to fulfill International Conference on Harmonization (ICH) requirements and this validation included specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, and robustness. The developed method could be incorporated into the USP monograph and applied for routine quality control analysis of erythromycin stearate tablets.

Enhancement of the properties of a drug by mono-deuteriation: reduction of acid-catalysed formation of a gut-motilide enol ether from 8-deuterio-erythromycin B

An efficient synthesis of 8-d-erythromycin B was achieved. A deuterium isotope effect suppresses formation of the corresponding enol ether, which may result in reduced gut-motilide effects.

Effect of the solvent on improving the recognition properties of surface molecularly imprinted polymers for precise separation of erythromycin

The results of ¹³C-NMR and isothermal titration calorimetry indicate that adding of NH₃·H₂O is able to prevent the electrostatic interaction between MAA and ERY-A and consequently prevent nonspecific adsorption and achieve higher specificity.

Synthesis and antibacterial activity of desosamine-modified macrolide derivatives

Structural factors behind erm macrolide resistance were studied through synthesis of new macrolide derivates possessing truncated desosamine sugar moieties and subsequent determination of their antibacterial activity. Synthesized compounds with 2'-deoxy and 3'-desmethyl desosamine rings demonstrated decreased antibacterial activity on the native Staphylococcus aureus strain and were inactive against constitutively resistance S. aureus. The obtained results indicate that steric repulsion between the dimethylated A2058 and desosamine ring cannot be considered as a primary reason for erm-resistance.

Mechanism for the degradation of erythromycin A and erythromycin A 2'-ethyl succinate in acidic aqueous solution

A major drawback of the antibiotic erythromycin A is its extreme acid sensitivity, leading to rapid inactivation in the stomach. The accepted model for degradation in aqueous acidic solution has erythromycin A in equilibrium with erythromycin A enol ether and degrading to anhydroerythromycin A. We report a detailed kinetic study of the acidic degradation of erythromycin A and of erythromycin A 2'-ethyl succinate (the market-leading pediatric prodrug), investigating the reaction rates and degradation products via NMR. This reveals that the accepted mechanism is incorrect and that both the enol ether and the anhydride are in equilibrium with the parent erythromycin. By implication, both the anhydride and enol ether are antibacterially inactive reservoirs for the parent erythromycin. The actual degradation pathway is the slow loss of cladinose from erythromycin A (or erythromycin A 2'-ethyl succinate), which is reported here for the first time in a kinetic study. The kinetic analysis is based on global, nonlinear, simultaneous least-squares fitting of time course concentrations for all species across multiple datasets to integrated rate expressions, to provide robust estimates of the rate constants.