The solubility test should be conducted using tablets from a representative commercial or pilot batch. The percentage of zinc in solution should be assessed under the following conditions:
- One tablet should be immersed in 5.0 mL water at room temperature. The vessel containing the tablet in water should be allowed to sit for one minute without any agitation. After the one minute, the solution should be filtered immediately e.g., using a syringe filter, and subsequently analyzed for zinc content.
- The quantity of zinc in solution should be calculated as a percentage of the total zinc in the tablet. It is expected that the reported percentage value will be close to the label claim (with tolerance for content and analytical variations)
- A sample size of at least six measurements (n≥6) should be conducted. If it cannot be established that the excipients present in the proposed product formulation do not significantly negatively impact the absorption of zinc, clinical study data demonstrating efficacy of the proposed product in the treatment of acute diarrhoea or in vivo bioavailability data demonstrating that administration of the proposed product produces adequate plasma levels of zinc within a 72-hour administration period, is required.