FaSSIF (Fasted State Simulated Intestinal Fluid) is a very useful drug development tool. Tests in this dissolution medium can reveal how your oral drug is likely to dissolve and potentially be absorbed in fluid from the upper intestine after drinking a glass of water.

The stability, solubility and dissolution data you generate from testing in FaSSIF can help identify critical factors influencing your drug’s absorption in the fasted state. This is especially important for water insoluble drugs. These results also support your selection of the appropriate solid state and formulation approach for your drug. Experiments are performed using standard laboratory equipment (such as USP Dissolution Apparatus 1 or 2). Drug content is analysed using HPLC.

What’s the composition of FaSSIF?

FaSSIF contains the same type and level of surfactants (bile salt and phospholipid) present in the gastrointestinal fluid it replicates. These surfactants are critical, particularly for poorly water-soluble drugs, because they form mixed micelles which can enhance drug solubility and dissolution greatly. This can have a big influence on how a drug is absorbed. FaSSIF has the average pH of fasted intestinal fluid and similar osmolarity (about 270 mOsmol/L) too. These are important parameters to control when testing drugs or formulations sensitive to pH and salt content.

How do I make FaSSIF?

You can make FaSSIF in no more than a couple of minutes with 3F Powder® and FaSSIF Buffer Concentrate. These simple steps show how easy it is to prepare 900mL of the medium (the volume we recommend using per dissolution vessel):

Our Media Preparation Tool will give you customized instructions for almost any volume of FaSSIF you want to make and it’s free to use here.

Download our Biorelevant Dissolution Guides here.