ABSTRACT
A method is described for the determination of erythromycin estolate by liquid chromatography. A C18 reversed-phase column (25 x 0.46 cm i.d.) was used with acetonitrile-tetrabutylammonium sulphate (pH 6.5, 0.2 M)-phosphate buffer (pH 6.5, 0.2 M)-water [x:5:5:(90-x), v/v/v/v] as mobile phase. The proportion of acetonitrile (x) has to be adapted to the type of stationary phase used. For RSil C18 LL 42.5% (v/v) was used. The column was heated at 35 degrees C, the flow rate was 1.5 ml min-1 and UV detection was performed at 215 nm. The main component, erythromycin A propionate, was separated from all other components which were present in commercial samples. The impurities most frequently observed were the propionate ester of erythromycin C and the amide N-propionyl-N-demethyl-erythromycin A. Erythromycin A was shown to be present in specialties.
Subject(s)
Chromatography, High Pressure Liquid , Erythromycin Estolate/analysis , Acetonitriles/chemistry , Erythromycin Estolate/chemistry , Magnetic Resonance Spectroscopy , Reference Standards , Spectrophotometry, UltravioletABSTRACT
A method is described for the determination of erythromycin ethylsuccinate by liquid chromatography. A C18 reversed-phase column (25 cm x 4.6 mm I.D.) was used with acetonitrile-0.2 M tetrabutylammonium sulphate (pH 6.5)-0.2 M phosphate buffer (pH 6.5)-water [x:5:5:(90-x)] as mobile phase. The proportion of acetonitrile (x) has to be adapted to the type of stationary phase used. For RSil C18 LL, 42.5% was used. The column was heated at 35 degrees C, the flow-rate was 1.5 ml/min and UV detection was performed at 215 nm. The main component, erythromycin A ethylsuccinate, was separated from all other components which were present in commercial samples. The main impurities were erythromycin A and the ethylsuccinate esters of erythromycin B and C. The amide N-ethylsuccinyl-N-demethylerythromycin A was shown to be present in all the samples examined. The method was successfully applied to the analysis of specialities.
Subject(s)
Chromatography, Liquid/methods , Erythromycin Ethylsuccinate/analysis , Erythromycin Ethylsuccinate/chemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry , Molecular StructureABSTRACT
A column-switching technique is described for LC of erythromycin. The method allows, in about 1 h, the separation of erythromycin A from all its known potential impurities, except erythromycin D, which is a minor impurity. The switching technique combines two columns (7.5 cm x 4.6 mm and 25.0 cm x 4.6 mm) both packed with RSil C 18 LL 10 microns. The mobile phase is acetonitrile-tetrabutylammonium sulphate (0.2 M, pH 6.0)-ammonium phosphate buffer (0.2 M, pH 6.0)-water (24:5:5:66, v/v/v/v). Temperature was 35 degrees C, flow rate was 1.5 ml min-1, detection was by UV at 210 nm. Results for a number of commercial samples of various origin are reported.
Subject(s)
Chromatography, High Pressure Liquid/methods , Erythromycin/analysis , Acetonitriles/chemistry , Buffers , Calibration , Erythromycin/analogs & derivatives , Quaternary Ammonium Compounds/chemistry , TemperatureABSTRACT
Erythromycin A (EMA) is a potent stimulator of gastrointestinal motor activity. In vitro studies suggest that it mimics motilin, a peptide that stimulates motor activity in human and in rabbit via smooth muscle receptors. We have compared the in vitro contractile effect of EMA and two derivatives, 8,9-anhydro-EMA-6,9-hemiketal (EM201) and EMA N-oxide, on rabbit duodenal smooth-muscle strips with their ability to displace iodinated motilin bound to crude smooth-muscle membrane fractions. The concentrations required to induce 50% of the maximum contractile response to a supramaximal dose of acetylcholine were 5.0 x 10(-8), 2.0 x 10(-6), and 1.0 x 10(-4) M for, respectively, EM201, EMA, and EMA N-oxide. The concentrations required to displace 50% of the labeled motilin were, in the same order, 1.0 x 10(-8), 1.3 x 10(-7), and 4.0 x 10(-6) M. Both parameters were well correlated. The dose-response curve of the EMA was parallel to that of motilin and the effects of motilin and EMA were additive. Contractions induced by EMA were insensitive to pretreatment with tetrodotoxin or atropine. EMA had no effect on muscle strips of rat or dog duodenum but did induce contractions in human strips. EMA was totally ineffective on ileal preparations, which are also unresponsive to motilin and in which motilin binding is absent. EMA has therefore the same regional and species specificity as motilin. We conclude that EMA is a motilin receptor agonist.
Subject(s)
Erythromycin/pharmacology , Receptors, Gastrointestinal Hormone/physiology , Receptors, Neuropeptide , Animals , Dogs , Erythromycin/metabolism , Humans , Muscle Contraction/drug effects , Muscle, Smooth/metabolism , Muscle, Smooth/physiology , Muscle, Smooth/ultrastructure , Rabbits , Receptors, Gastrointestinal Hormone/drug effects , Receptors, Gastrointestinal Hormone/metabolismABSTRACT
Tissue distribution and excretion of radioactively labelled compounds was studied in the Wistar rat after i.v. administration of [N-methyl-14C]-erythromycin A. Whole-body autoradiography and liquid scintillation counting was used to investigate the tissue localization of radioactivity in pregnant and non-pregnant rats. Tissue levels were maximal within 20 min, except for lachrymal glands, thymus and brain. Large amounts of radioactively labelled compounds, partly originating from active secretion, were present in the small intestine and caecum. Marked concentration of radioactively labelled compounds was also observed in the liver, spleen, lachrymal and salivary glands, lymph nodes, mammary glands, skin, bone marrow, and, to a lesser extent, in the lung, kidney and skeletal muscle. During six hours of experimental follow-up, plasma levels remained lower than corresponding tissue levels. At 1 h the radioactivity in fetuses was about three times lower than that in maternal blood. Within 48 h, more than 90% of the administered radioactivity was excreted. The amounts of radioactivity recovered in urine, faeces and expired air were about 19%, 48% and 24% respectively. After 48 h, 8% of the administered radioactivity was found in the carcass.
Subject(s)
Erythromycin/analogs & derivatives , Animals , Autoradiography , Erythromycin/pharmacokinetics , Female , Placenta/metabolism , Pregnancy , Rats , Rats, Inbred Strains , Tissue DistributionABSTRACT
Important interlaboratory variation was obtained for the water content of erythromycin samples as determined by the Karl Fischer method. It is demonstrated that the variation is related to the type of reagents used. In poorly buffered systems erythromycin enol ether and water are formed by acid degradation of erythromycin. However, when an appropriate solvent is used, accurate titration of water in erythromycin is possible. A 10% m/v solution of imidazole in methanol is preferred to pyridine or a mixture of pyridine and methanol for it has a good buffer capacity, it lacks the unpleasant odour of pyridine and it allows a high titration speed.
ABSTRACT
An improved high-performance liquid chromatographic method for analysis of erythromycin is described. The separation can be performed under mild conditions of pH (6.5) and temperature (35 degrees C) on C8 and C18 silica-based reversed-phase materials of different origins. The mobile phase, with a flow-rate of 1.5 ml/min, contained various amounts of acetonitrile (25-40%, v/v), 5% (v/v) 0.2 M ammonium phosphate buffer pH 6.5, 20% (v/v) 0.2 M tetramethylammonium phosphate and water. UV detection at 215 nm allows quantitation of erythromycins A, B and C, N-demethylerythromycin A, erythromycin A enol ether and anhydroerythromycin A. The column history plays a major role, older columns often giving better separations.
