Beyond Pharmacology: Do Tablet Shape, Size, and Color Influence Medication Adherence in Psychiatric Outpatients?

Background

Medication nonadherence is a multifaceted challenge in psychiatric treatment, driven by clinical, psychosocial, and patient factors. An understudied aspect is the physical properties of solid oral dosage forms (SODFs)-shape, size, and color-which may influence acceptability and adherence. Yet, quantitative evidence connecting real-world preferences to adherence outcomes is scarce, especially in psychiatric settings.

Objective

To evaluate preferences for tablet shape, size, and color among psychiatric outpatients and their relation to self-reported adherence.

Methods

This cross-sectional observational study, conducted over 6 months (April-October 2024) in a tertiary psychiatric unit, included 232 patients with varied psychiatric diagnoses on oral medications. Sociodemographics, clinical details, and preferences/dislikes for tablet attributes (shape: flat circular vs oval/oblong; size: small, medium, large; color: white, yellow, red, blue) were gathered via a structured questionnaire. Adherence was measured using the validated 10-item Medication Adherence Rating Scale (score ≥6=adherent). Associations were analyzed with χ2 and Fisher exact tests (P<.05).

Results

The cohort (mean age: 36±13.3 years; 65.1% male) had 74.1% adherence (95% CI, 68.1-79.3%). Preferences included oval/oblong shapes (43.5%), small sizes (41.4%), and white colors (41.8%); dislikes were large sizes (53.4%), flat-circular shapes (40.5%), and red colors (33.6%). No significant links existed between preferences/dislikes and adherence (all P >.05; χ2 = 1.90-4.64; Cramér's V=0.09-0.14). Adherence rates varied by diagnosis (lowest in psychosis: 30.8%; 95% CI, 12.7-57.6% and highest in generalized anxiety disorder: 85.0%; 95% CI, 64.0-94.8%) but nonsignificantly (χ2 =16.70, P= .081, Cramér's V=0.27).

Conclusion

Psychiatric patients show distinct esthetic preferences for tablets, consistent with prior acceptability research, but these do not predict adherence. Clinical symptoms, illness insight, and therapeutic alliance appear to dominate. Strategies should emphasize psychosocial interventions rather than formulation esthetics. Prim Care Companion CNS Disord 2026;28(4):25m04101. Author affiliations are listed at the end of this article.