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Why do Some Drugs have Multiple Dissolution Methods?

The USP and FDA both have Dissolution Method Databases which can help with developing a method for your product. But why do some drugs have multiple dissolution methods in the USP and FDA? How do you choose?

Going through these databases, you will find some products with 1 method and some products with several methods. If you are in a situation where you are developing a dissolution method for a product and multiple methods exist - here are some things to consider:

Multiple methods exist due to some fundamental differences between different formulations of the same drug product. Some of these differences could be the length of release (immediate release, enteric coated, extended release). The product may also differ in the type of formulation such as non-disintegrating tablet, disintegrating tablet, capsules (filled with oil, beads, powders, etc.), and so on. When looking at these methods, consider the goals of the product you are working on and consider which of these methods most closely matches your product type.

Similarites between multiple methods can be helpful to consider as well. You may find that there are 3 methods - but all using the same or very similar medias. This can help narrow down your method development a bit.

Methods in the USP and FDA are not complete. They are a good starting point in method development - but they do not give you all the information that you need to know about a final method. Filter choice and filter conditions are a key element that will been to be determined. Other factors that may not or are not included in these methods may be sinker choice, basket mesh, product preparation and introduction (such as with suspensions), sample and standard stability, and so on. You will always need to develop the method and validate it for your product - even if there is a method shown in these databases.

It is also important to know that you may find that none of the methods listed in the database are acceptable for your product! Multiple methods exist because the previous methods didn't work - and you may need to develop the next method for this drug. Methods that you find in these databases are not current, they're often at least 10 years old. Formulation technologies change quickly and older methods may not be suitable. One example of formulation changes being seen is the drive to make drug particles smaller and smaller with nanoparticles and microparticles. This is a big advance in drug development - but it does pose new challenges in making dissolution methods.

The USP and FDA Dissolution Method Databases are excellent places to start your method development, but they are not the ending point. Take a look, see if they may fit your product, and if so - get to work further developing them.

Read also: What is Q Value in Dissolution Specification?

Resource Person: Ken Boda (Dissolution Product Specialist at Agilent Technologies)

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