What Shape and Size of Tablets Do Our Patients Prefer?
The size and shape of tablets can affect patients' compliance with treatment. The following article provides an overview of conclusions from two foreign studies focused on influencing the difficulty of swallowing and handling tablets depending on their shape and size.
Size and Shape of Tablets Matter
Tablets and capsules are among the most frequently used forms of medicinal products. Large tablets are more difficult to swallow, which can result in poorer compliance with treatment. Therefore, it is very important to understand their preferences regarding the size and shape of tablets. This issue has been addressed by some previously conducted studies. For example, a retrospective study showed that patients consider a tablet too large if the sum of its main axis, minor axis, and thickness is 21 mm.
Handling and Swallowing Depending on Size
To verify the results of the mentioned study and gain new insights, a study was conducted in Japan to evaluate patients' preferences regarding the size of tablets in all three dimensions. Using 3D printing, a total of 18 different tablet samples of cylindrical, elongated, or oval shapes with varying sizes were made from polylactic acid. The study involved 40 patients − pharmacy visitors, who assessed the difficulty of handling and swallowing the tablet by touch and observation. They then filled out a questionnaire with their conclusions. A visual analog scale (VAS) was used to evaluate both observed variables (the lower the value, the easier the handling or swallowing, and vice versa) and the relationship between the VAS score and the main axis of the tablet, its thickness, and the sum of the main and minor axes (I2), and the sum of the main axis, minor axis, and thickness (I3).
Regarding the evaluation of the difficulty of handling the tablets, small samples generally showed higher VAS scores than large samples. It was particularly challenging for patients to handle samples with a thickness of 2 mm or less. The dimension of the main axis did not have a significant impact. According to the obtained data, women reported lower VAS scores for the difficulty of handling the sample compared to male participants. Capsule-shaped samples received worse evaluations.
When evaluating the difficulty of swallowing tablets, large samples scored higher on the VAS than small ones. The dimension of the main axis did not affect the assessment of swallowing difficulty. Tablets with a thickness ≥ 6 mm were particularly challenging to swallow. Patients taking more medications had higher VAS scores when evaluating swallowing difficulty compared to those taking fewer medications.
An I3 value > 20–22 mm was generally associated with negative evaluations from the participants. Age, disease, and ingestion problems did not have a significant impact on the results.
Swallowing Difficulty Depending on Shape
A controlled randomized crossover study focused on determining the difficulty of swallowing comparably sized tablets of different shapes, most of which were made of isomalt using 3D printing.
In the blinded study, 6 3D-printed tablet samples and 2 pressed samples were tested. Twelve participants filled out a questionnaire in which they assessed the difficulty of swallowing, the sensation of a foreign object at the moment of swallowing, the persistent sensation of a foreign object after swallowing, and pain after swallowing. The amount of water consumed after administration was also recorded. The best results were achieved by 3D-printed and pressed elongated tablets, followed by 3D-printed and pressed round tablets, and then rugby ball-shaped and spherical tablets. Tablets in the shape of a pyramid and those of a cuboctahedron shape performed the worst.
Final Summary
Based on the resulting findings, we can say that tablets and capsules with a thickness of 6 mm or more are more difficult to swallow, whereas tablets with a thickness of ≤ 2 mm are more difficult to handle. The dimension of the main axis of the tablet did not have a significant impact on evaluation. 3D printing allows for the production of tablets of very diverse shapes, but it appears that it is necessary to verify whether they are easy for patients to swallow. Not every tablet shape is easy to swallow, especially if it is not sufficiently rounded.
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Sources:
- Kabeya K., Satoh H., Hori S. et al. Experimental study on patient preferences regarding the shape and size of medical tablets and capsules using three-dimensionally printed plastic model formulations. Patient Prefer Adherence 2021; 15: 863–870, doi: 10.2147/PPA.S306582.
- Bogdahn M., Torner J., Krause J. Influence of the geometry of 3D printed solid oral dosage forms on their swallowability. Eur J Pharm Biopharm 2021 Oct; 167: 65−72, doi: 10.1016/j.ejpb.2021.07.009.
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