Abstract

A significant proportion of the population, including children and elderly have difficulty in swallowing solid oral dosage forms. This problem becomes more acute for the administration of sustained release dosage forms due to increase in the volume of delivery system. Oral liquid suspensions are majorly designed to make dosage forms more palatable to paediatric and convenient to geriatric patients. However, their controlled release form is tricky due to the chances of premature release of the API in the suspending media during storage. This produces a significant challenge and accounts for the fact that there are few sustained release oral suspension formulations.

From formulation perspective, these systems make use of two technologies; ion exchange and membrane diffusion control. The system is formed by reacting a drug in its ionic state with a suitable ion exchange resin. A polymeric coating is then applied to the complexed particles to form a water soluble but ionic and drug permeable coating. To be effective this system requires, that drug interacts ionically with the ion exchange polymer. Since the ion concentration in human GI tract is remarkably consistent, drug release is quite precise and is unaffected by variations in pH, temperature or contents in stomach or intestine. In addition to prolonged release, the system makes the drug tasteless, which is helpful in masking the bitter taste of many actives.

For a development scientist this complex system throws up many challenges such as selection of ion exchange resin, its ratio, the coating polymer and so on. To add to these challenges the process of manufacturing is lengthy and requires lot of controls. Eventually, testing of the product is yet another challenge as ion exchange is a reversible process and makes extraction of drug from resinate quite difficult. Thus, overall the development of such a formulation turns out to be an acid test for all - formulator, analyst, regulatory and production scientist. The presentation will dwell upon basics of the system along with associated development challenges and some potential solutions. 

Oral liquid suspensions are majorly designed  for the patients with difficulty in swallowing. But their controlled release form is also tricky due to the chances of premature release of the API in the suspending media during storage. This produces a significant challenge and accounts for the fact that there are few sustained release oral suspension formulations.