Bioequivalence of Metolazone Preparations
For a number of years Metolazone tablets have only been available in the UK on prescription using an imported version from Canada. Recently Renascience Pharma has launched a licensed version of the 5mg tablets called Xaqua®, the 2.5mg strength are still only available as an import.
Comparative bioavailability studies have shown that the bioavailability of Xaqua® 5mg tablets may differ significantly by up to approximately two-fold to other metolazone products. This means that a dose adjustment will be needed when patients are switched between products.
Numark Information Services team have recently received a number of calls questioning why their usual route of supply has changed as specials companies are directing pharmacies to obtain the licensed version rather than an import.
Although the clinical impact of the difference in bioavailability of the licensed version is unclear, it can be assumed that vulnerable patients such as the elderly or those with renal failure may be at increased risk of adverse effects.