Navigate your solid form salt landscape with the Crystal16
The term pharmaceutical salt is used to refer to an ionizable drug thathas been combined with a counter-ion to form a neutral complex. More than half of all drug molecules on the market are salts. The main reason behind this is that in general salts have more desirable aqueous solubility (and implicitly bioavailability) profiles compared to the free acid or the free base API (Active Pharmaceutical Ingredient).
Transforming an API into a salt has several other benefits, with different physico-chemical and mechanical properties available, such as dissolution profile, stability, and manufacturability in solid formulations. The difference between the physico-chemical properties of different salts of the same API can be so great, that it has been said that ‘changing the salt is changing the drug’.
This is true in the legal context as well, as new API salts are patentable. Therefore, salt screenings have become increasingly important for protecting your intellectual property, and not only as a way of improving and tuning your APIs properties.
This application note discusses the most important salt screening challenges and methods, using the Crystal16 instrument in the process.
Content overview:
- Why formulate APIs as salts
- Salt Screening Challenges
- Examples of some of the most widely used acids and bases
- Salt screening methods:
- In-situ salt screening
- Saturated solution method
- Cooling evaporative method
- Characterizing your salts
- Conclusion
