When talking about excipients in solid dosage form development, the topic can become somewhat confusing. Because there are not only different chemical compounds, but some of them also come in many different grades. In addition, there are various manufacturers of excipients who all claim to have the ideal compound. Most of these excipient grades have their justification and although chemically identical, the right choice depends on the function they are intended to fulfil.
Differences can be found in particle size, morphology and the manufacturing methods. For example, spray dried materials show in general good bonding capacities and excellent flow properties. Due to the more complex production method, they are generally more expensive. And their advantages in bonding capacity and flow are often lost during a granulation step. That is why they are mainly used for direct compression or as post-granular excipient.
If, on the other hand, an attempt is made to improve the tableting properties with the crystalline grade of mannitol which is used as filler in wet granulation, this will not be successful.
This are just two examples why choosing the right excipients can be challenging.