Metoprolol characteristics

GS Rekhi, ND Eddington, MJ Fossler, P Schwartz, LJ Lesko, LL Augsburger. Evaluation of in vitro release rate and in vivo absorption characteristics of four metoprolol tartrate immediate release tablet formulations. Pharm Devel Tech 2(1) 11-24, 1997. 

Interestingly, similar transport experiments by Heard et al. [19] using human skin showed no differences in the permeation profiles of R- and S-propranolol from donor solutions of both the racemate and the pure enantiomers. Similar findings were further reported for the enantiomers of metoprolol [32] and ketoprofen [33] and for the diastereomers of ephedrine [18] no significant differences were found in the permeation profiles of optical antipodes across skin from donor solutions containing the racemate. For example, when the permeation characteristics of individual enantiomers of metoprolol free base (MB) were investigated using hairless mouse skin, the permeation profiles of R- and S-enantiomers of MB from donor... 

The chromatographic parameters (retention factors, efficiencies and asymmetry factors) obtained with the selected SDS micellar and methanol-water mobile phases are shown in Table 10.3. The elution order is the same in both cases, except for celiprolol, metoprolol and timolol, which eluted at close times with the micellar eluents. On the other hand, the peaks obtained with the SDS-propanol eluents had better characteristics than the peaks in the aqueous-organic eluents, with a tenfold increase in efficiency for some P-blockers. The peaks in the aqueous-organic mobile phases were often very asymmetrical. The determination of the whole set of drugs was possible with a unique micellar mobile phase, with retention times of less than 15 min, whereas two different aqueous-organic mobile phases were needed to make the same analyses. 

The effects of different temperatures on the separation of all three j8-blockers using L-aspartic acid as a chiral selector were also investigated. It has been found that 17°C was the most suitable temperature for the resolution of the examined jS-blockers, providing desired mobility to the diastereomeric ion pair formed anionic species of L-aspartic acid and protonated cations of amino moieties of the corresponding )3-blockers. The presence of chiral selector in situ was established by treating the developed chromatograms with ninhydrin that produced a characteristic color with aspartic acid in both spots of the resolved enantiomers [18]. This method was very sensitive, enabling detection of 0.26 fig atenolol and 0.23 tig of each metoprolol and propranolol. 

The most important characteristic of the chiral recognition is that the chiral selector, either present in mobile phase or impregnated in the stationary phase, has to be compatible in size and structure with the racemic species to be resolved. This approach has been used by LuCid et al. [20] who developed a method for the separation of ( )-metoprolol tartrate. In order to approach the separation, the... 

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