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Compounding Advice - Metoprolol suspension

Compounding Advisory Group
Formulation Question and Answer


Question: Metoprolol suspension with brand switched metoprolol Feb 2017
Since the NZ standardised formulation batch sheet for metoprolol suspension specifies Lopressor™ but the PHARMAC community schedule has Apo-Metoprolol™ as the sole subsidised product and the disclaimer on  the compounding batch sheet on the pharminfotech and PSNZ websites state “Please note brand changes may impact on the formulation provided. Do not substitute different brands without confirming if this is appropriate.” is there a plan to review the standardised formulation for metoprolol suspension?

Answer:
It is possible that switching brands from those specified in the standard batch sheets may alter the chemical and physical stability of an oral liquid made from tablets. This is poorly studied and not very well recognised. We will be discussing this in more detail when the Compounding Advisory Group meets in late March.
In the meantime, our opinion is that the risks associated with switching brands from Lopressor to the Apo brand are low and we have no reports or indications of problems. Metoprolol tartrate is very soluble and relatively stable in solution at the pH of Ora-Plus. It appears unlikely that tablet excipients would significantly alter chemical or physical stability.  Ideally, formulations using different brands should be formally studied and we will be making recommendations along these lines. 
The Compounding Advisory Group will communicate further guidance as it develops. In the meantime, as mentioned in the bulletin, we encourage any concerns to be reported.


David Woods
For Compounding Advisory Group