Assessing lay beliefs about generic medicines: Development of the generic medicines scale.

The aims of this study were to develop a scale to assess lay beliefs about generic medicines, and to investigate whether these beliefs differ according to demographic factors in an opportunistic general public sample. In the pilot study, the participants were 92 men and 136 women, and in the main study there were 314 men and 505 women. At both stages, the participants completed a questionnaire measuring beliefs about generic medicines, preference for medicines and demographic information. The scale has good face validity, showing a satisfactory level of internal consistency. An exploratory principal component analysis revealed a two-factor structure concerning beliefs about generic medicines, comprising two core themes (efficacy and similarity to brand medicines), in two different samples. Older participants showed a stronger belief in similarity with brand names than the younger group. Higher educated participants showed a stronger belief in the efficacy of generics. The opportunity to assess beliefs about generic medicines may have implications for adherence, for the implementation of health policies and for decision making about medicines.