Acetaminophen (paracetamol) is available in a wide range of oral formulations designed to meet the needs of the population across the age-spectrum, but for people with impaired swallowing, i.e. dysphagia, both solid and liquid medications can be difficult to swallow without modification. The effect of a commercial polysaccharide thickener, designed to be added to fluids to promote safe swallowing by dysphagic patients, on rheology and acetaminophen dissolution was tested using crushed immediate-release tablets in water, effervescent tablets in water, elixir and suspension. The inclusion of the thickener, comprised of xanthan gum and maltodextrin, had a considerable impact on dissolution; acetaminophen release from modified medications reached 12-50% in 30 min, which did not reflect the pharmacopeia specification for immediate release preparations. Flow curves reflect the high zero-shear viscosity and the apparent yield stress of the thickened products. The weak gel nature, in combination with high G' values compared to G'' (viscoelasticity) and high apparent yield stress, impact drug release. The restriction on drug release from these formulations is not influenced by the theoretical state of the drug (dissolved or dispersed), and the approach typically used in clinical practice (mixing crushed tablets into pre-prepared thickened fluid) cannot be improved by altering the order of incorporation or mixing method.
Keywords: Acetaminophen; dissolution; dysphagia; rheology; viscosity.