Solid oral dosage forms such as tablets and capsules are often crushed and mixed with foods or fluids to aid drug delivery for those who cannot or prefer not to swallow them whole. Some people have a physiological problem limiting swallowing (dysphagia), and their fluids are thickened to ensure safe swallowing; these thickened fluids are also used to deliver crushed medication in replacement of water. This thesis explores the issues surrounding the swallowing of whole tablets and capsules, their modification by crushing and the influence of coadministration with thickened fluids on absorption pharmacokinetics. The literature review (Chapter 1) examines the physiology and pathophysiology of swallowing and considers the particular issues surrounding swallowing tablets and capsules. It also explores the possible consequences of crushing the medications and mixing the powder with vehicles such as jam, honey, yoghurt and thickened water.This thesis contains two sections. In Section A (Chapter 2), the potential influence of psychological issues, oral sensation, sensory effect and motor ability of an individual on swallowing pills was investigated. It is hypothesised that swallowing tablets and capsules will be an issue in people with a memory of gagging on food and medication, strong gag reflex, heightened taste sensation, or who tend to chew their food for extended periods.Volunteers (153) completed a written survey and one-on-one assessments. Psychological issues were addressed by questions on memory of choking incidents on food or medication, and regularity of medication use. Sensory effects were assessed by measuring the person's gag reflex, taste receptor density, size of the mouth (mallampati classification), and on food neophobia. Motor effects were assessed as efficiency in chewing a jelly snake. Finally, the volunteers were observed swallowing a capsule and the quantity of water used, and head position was recorded.In the survey, 33% of the population reported that they have had trouble swallowing medication.These people were more likely to have choked on medication in the past, have a smaller mouth cavity, and a medium or high taste receptor density. There was no relationship between trouble swallowing medication and gag reflex, food neophobia, chewing efficiency, quantity of water used to swallow, and head position.In Section B (Chapters 3, 4, and 5), the effect of crushing medication and mixing with water thickened with a commercial thickening agent on absorption pharmacokinetics was studied.ii Paracetamol tablets were used as the model drug, and saliva samples were used to measure the PK profile. Chapter 3 assessed the inter-and intra-individual variability as the coefficient of variation of paracetamol in saliva. Volunteers took whole tablets of paracetamol (2 x 500 mg) on two different days separated by a week. Saliva production was stimulated using citric acid and paracetamol levels in the saliva were measured using high-performance liquid chromatography. Non-compartmental pharmacokinetic analy...