Improving solubility – a close look at available approaches

The need to improve the solubility of active pharmaceutical ingredients (APIs) has been rising for decades. Today, this need is increasingly pressing, as the number of APIs that are poorly water-soluble (based on their BCS classification) is growing: while around 40% of APIs on the market show poor solubility, approximately 60% of new molecular entities (NMEs) have been reported to have solubility challenges, which represents a significant increase.

As a result, solubility-enhancing techniques have become an area of focus for pharmaceutical formulators. But why is the solubility of an API deemed so important in the pharmaceutical world? For an oral formulation, API solubility and permeability are critical factors for the absorption of the API in the gastrointestinal tract and its bioavailability at the site of action.

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However, the need for APIs with a good solubility or, where this is not the case, the need for ways to enhance solubility is not limited to oral formulations but is also a prerequisite for parenteral administration forms, as injectables or subcutaneous injection typically require the API to be present in a solubilized form.

Different approaches to solubility enhancement are available (see Figure 1). Chemical approaches such as salt and prodrug formation are typically more feasible in early development stages, as they fundamentally alter the API’s chemical nature. Download the whitepaper here: improving-solubility-whitepaper-wp3252en-mk.pdf

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