Excipients are key ingredients in the pharmaceutical industry. Furthermore, the demand for controlled release formulations is expanding, considering the trend of greater comfort linked to the use of drugs. Extended-release products have reduced dosing frequencies, which are particularly beneficial for pediatric and geriatric patients, but are appreciated by most patients and in general lead to improved medication adherence. Reformulation of branded drugs in controlled-release formats is one of the most common methods for extending the product lifecycle. Generic drugs are also often formulated with controlled-release properties.

How controlled release is achieved?

Controlled-release “behavior” can be achieved by using polymeric coatings on solid dosage forms or by incorporating various types of polymer matrix systems, enzyme-activated systems, or systems that respond to changes in physical conditions within of the formulation. Mechanisms include dissolution, diffusion, osmotic pressure, maintenance of a hydrological or hydrodynamic equilibrium and ion exchange. Newer approaches based on nanotechnologies and new matrix technologies are currently under development and include administration of retarded controlled release drugs, floating systems and mucoadhesive systems for the regulated release of antiviral drugs.

The role of the excipients in controlled release

Excipients are key ingredients in controlled release formulations. They contribute to the formation of the matrix in the systems that use it and act as polymeric membranes for powders and multi-particulate systems in the forms of oral solid dosage (OSD). In oral liquid products, the excipients can also provide taste masking and protection for the gastric mucosa. In other specific cases, the excipients can be a deterrent to abuse and help to avoid alcohol-induced dumping. The excipients that provide controlled-release characteristics to oral solid dosage forms not only allow control of the API release rate, but also target the district where the release occurs.

New options

Since the excipients are key ingredients in controlled release formulations, it may seem surprising that the choices are somewhat limited, particularly for some patient populations such as pediatric populations. Suppliers are developing “new” excipients that can provide solutions and support for moving existing formulations into new areas, but the excipients do not have their own approval path. For this reason, pharmaceutical companies are reluctant to take on the responsibility of toxicology and clinical trials with an untested material because they run the risk of endangering the approval of their new pharmaceutical applications. Therefore, most of the new excipients used derive from modifications or combinations of previously approved excipients.