Metoprolol immediate-release

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. 

Metoprolol CR/XL, carvedilol, and bisoprolol are the only /J-blockers shown to reduce mortality in large HF trials. It cannot be assumed that immediate-release metoprolol will provide benefits equivalent to metoprolol CR/XL. Because bisoprolol is not available in the necessary starting dose of 1.25 mg, the choice is typically limited to either carvedilol or metoprolol CR/XL. On the basis of regimens proven in large clinical trials to reduce mortality, initial and target oral doses are as follows ... 

Tablets, extended release - The extended-release tablets are for once daily administration. When switching from immediate-release metoprolol tablets to extended-release, use the same daily dose.

There also has been much debate about whether carvedilol is superior to metoprolol or bisoprolol and whether immediate-release metoprolol has equivalent efficacy to metoprolol CR/XL, the formulation studied in the MERIT-HF trial. Despite the differing properties of carvedilol versus metoprolol or bisoprolol, the clinical trials data provided little evidence for superiority of one drug over another. Specifically, mortality reduction versus placebo for each of these drugs was identical (34% to 35%). Yet questions persist about potential superiority of carvedilol, in part because it appears to be superior in its effects on certain parameters, such as change in EF, and certain hemodynamic responses at peak exercise. ... 

There is now reasonable evidence that immediate-release metoprolol tartrate is inferior to carvedilol, but controversy remains about the equivalency of metoprolol succinate CR/XL (Toprol-XL) and carvedilol. Some practitioners believe that the evidence suggests that carvedilol is superior, whereas others believe that any of the drugs (bisoprolol, carvedilol, or metoprolol CR/XL) are appropriate for management of chronic heart failure. 

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