At some point in our lives, many of us will have experienced indigestion, acid reflux or heartburn – often after a period of over-indulgence – the symptoms of which are not pleasant!

Recent research suggests that in some people acid reflux disease can be caused by abnormal movements of the muscles in the esophagus.

Formulating the perfect remedy

When faced with this situation, many turn to over-the-counter liquid indigestion remedies for relief. These formulations typically contain antacids that neutralize stomach acid and alginates that sooth the pain by coating the walls of the stomach and esophagus. Such products are fluid- particle suspensions so the size and distribution of particles present not only influences the pharmaceutical effect and speed of efficacy, but also the rheological characteristics of the formulation

Particle size affects bioavailability

Those particles of an active ingredient in suspension that are relatively small will be absorbed into the bloodstream more rapidly than larger ones. The ideal formulation for fast relief might therefore exhibit a small population of fine particles, that could be rapidly absorbed to provide instant action, and a population of larger particles to extend that relief over a prolonged period.

However, particle size and distribution also have a strong influence on viscosity which affects customer perception, ease of swallowing, and product stability. Overly viscous products may be unpleasant to use while products with very low viscosity and/or larger particles are more prone to settling, increasing the risk of non-uniform dosing. Viscosity can be fine tuned through the manipulation of solids concentration, particle size and distribution, and through the inclusion of viscosity modifiers.

The application of rheological analysis in the optimization of particle size is therefore essential to balance bioavailability,  patient perception and stability towards a quality product.


Of course, for those of us who are not yet at the point where our esophageal muscles are permanently damaged, it might just be more sensible to resist the temptation to eat or drink too much in the first placeā€¦ not that I ever could!!