Older adults represent the major target population for oral medications, due to the high prevalence of multimorbidity. To allow for successful pharmacological treatments, patients need to adhere to their medication and, thus, patient-centric drug products with a high level of acceptability by the end users are needed. However, knowledge on the appropriate size and shape of solid oral dosage forms, as the most commonly used dosage forms in older adults, is still scarce. A randomized intervention study was performed including 52 older adults (65 to 94 years) and 52 young adults (19 to 36 years). Each participant swallowed four coated placebo tablets differing in weight (250 to 1000 mg) and shape (oval, round, oblong) in a blinded manner on three study days. The choice of tablet dimensions allowed for a systematic comparison between different tablet sizes of the same shape, as well as between different tablet shapes. Swallowability was assessed using a questionnaire-based method. All tested tablets were swallowed by ≥80% of adults, independent of age. However, only the 250 mg oval tablet was classified as well swallowable by ≥80% of old participants. The same was true for young participants; however, they also considered the 250 mg round and the 500 mg oval tablet as well swallowable. Furthermore, swallowability was seen to influence the willingness to take a tablet on a daily basis, especially for an intake over longer time periods.

Swallowability, visual perception, and any handling to be conducted prior to use are all influence factors on the acceptability of an oral dosage form by the patient. Knowing the dosage form preferences of older adults, as the major group of medication end users, is needed for patient-centric drug development. This study aimed at evaluating the ability of older adults to handle tablets as well as to assess the anticipated swallowability of tablets, capsules, and mini tablets based on visual perception. The randomized intervention study included 52 older adults (65 to 94 years) and 52 younger adults (19 to 36 years). Within the tested tablets, ranging from 125 mg up to 1000 mg in weight and being of different shapes, handling was not seen as the limiting factor for the decision on appropriate tablet size. However, the smallest sized tablets were rated worst. According to visual perception, the limit of acceptable tablet size was reached at around 250 mg for older adults. For younger adults, this limit was shifted to higher weights and was dependent on the tablet shape. Differences in anticipated swallowability with respect to tablet shapes were most pronounced for tablets of 500 mg and 750 mg in weight, independent of the age category. Capsules performed worse compared to tablets, while mini tablets appeared as a possible alternative dosage form to tablets of higher weight. Within the deglutition part of this study, swallowability capabilities of the same populations were assessed and have been reported previously. Comparing the present results with the swallowing capabilities of the same populations with respect to tablets, it shows adults’ clear self-underestimation of their ability to swallow tablets independent of their age.

Gastric water emptying as a critical parameter for oral drug absorption can be investigated by several imaging techniques or by the interpretation of pharmacokinetics of appropriate substances. Recently introduced salivary caffeine kinetics is a valuable tool, but the required caffeine abstinence limits its applicability. To avoid the caffeine abstinence, stable isotope-labeled caffeine might be used, but the representability and transferability of kinetics for evaluation of gastric emptying must be demonstrated. Thus, salivary caffeine pharmacokinetics were compared for naturally occurring 12C-caffeine and 13C3-caffeine after the administration of water under fasting conditions in six healthy young subjects. For this purpose, an ice capsule containing the two caffeine species was administered with 50 mL tap water. Gastric water emptying was simultaneously quantified using magnetic resonance imaging (MRI). Gastric emptying of 50 mL of water could be successfully evaluated. The salivary caffeine kinetics of 13C3- and 12C-caffeine were nearly congruent and showed good linear correlations in all subjects, with a mean correlation coefficient of 0.96 in pooled data. Thus, the substitution of natural 12C caffeine with stable isotope-labeled 13C3-caffeine offers the opportunity for broader application of the salivary caffeine gastric emptying technique and increases the robustness of the method against environmental contamination with caffeine.