Modified medication use in dysphagia: the effect of thickener on drug bioavailability-a systematic review.

Introduction: Dysphagia is associated with long-term conditions including strokes, dementia, Parkinson's disease and frailty. Dysphagia affects 30-40% of the population aged over 65 years-old. Adults with dysphagia often experience long-term conditions requiring multiple medications (often > 5) to manage these. The thickening of liquids is a common compensatory strategy in dysphagia management. Studies suggest that immersion in thickened liquids affects medicines' solubility in vitro. Clinicians and pharmacists are unaware of the pharmacokinetic/therapeutic effects of thickened liquids on oral medicines. We conducted a systematic review of existing literature on thickeners' effects on drug bioavailability.

Methodology: We performed a literature search of MEDLINE & EMBASE. Search terms included: dysphagia/thickened diet (EMBASE only)/ bioavailability or absorption of medicines or pharmacokinetics; excluded: NG feeds/animal studies.

Studies Included: all genders, countries, > 18 years, community and hospital settings. PRISMA guidance was followed.

Results: Five hundred seventy results were found, and 23 articles identified following the reference list review. Following an abstract and full-text review, 18 were included. Most articles evaluated thickeners on dissolution profiles in-vitro, with a few investigating in-vivo. Most studies were single-centre prospective studies identifying that thickeners generally affect dissolution rates of medications. Few studies assessed bioavailability or used clinical outcomes.

Conclusion: Dysphagia and polypharmacy are common in older adults, but little is known about the effects of altering liquid viscosity on the therapeutic effect of most medications. Further larger-scale studies are required to evaluate the therapeutic impact of thickener, on a bigger range of medications, factoring in other variables such as type of thickener, viscosity of thickener and duration of immersion.