Experimental study on patient preferences regarding the shape and size of medical tablets and capsules using three-dimensionally printed plastic model formulations

Background: Tablets and capsules are the most common dosage forms. However, ease of use and/or swallowing influences patients’ compliance. Objective: To identify patients’ preferences regarding the three-dimensional size of medical tablets/capsules. Methods: Eighteen cylindrical-, oblong-, and oval-shaped model formulations having different sizes were prepared by three-dimensional printing using polylactic acid. Participants (40 patients visiting a pharmacy in Japan) evaluated the difficulty of picking up and swallowing these model formulations by touching/observing them, and completed a questionnaire. The visual analogue scale (VAS) was used to evaluate each sample, and the relationship of VAS scores to the major axis, thickness, I₂ (the sum of major/minor axes) and I₃ (the sum of major/minor axes and thickness) of the model formulations was evaluated by ANOVA followed by Tukey’s test. Results: Female participants showed lower VAS scores (less difficult) for picking difficulty compared with male participants, and those taking many drugs showed higher VAS scores (more difficult) for swallowing difficulty compared with those taking fewer drugs. Otherwise, age, gender, disease status, number of drugs usually taken, and ingestion problems did not greatly influence the evaluation. Overall, larger model formulations showed less picking difficulty, but greater swallowing difficulty. Model formulations 2 mm thick or less were harder to pick up, whereas those 6 mm thick or more were harder to swallow. I₃ values greater than 20–22 mm were associated with a negative evaluation by participants. Conclusion: Participants in this study preferred model formulations with an I₃ value below 22 mm and a thickness of 2–6 mm.