Generic substitution: additional challenge for adherence in hypertensive patients?

Objective: This study aims to investigate whether, and in what way, generic substitution affects drug adherence in hypertensive patients.

Methods: Personal interviews with 174 Norwegian patients (50-80 years) who had had their brand-name antihypertensive drug generically substituted were conducted using a semi-structured questionnaire.

Results: On average, 4.4 (1-14) prescription drugs were used by the participants. Of these, 2.0 (1-4) drugs were antihypertensives. More than 50% of the patients had been using antihypertensive drugs for more than 10 years. One in four found it difficult to remember to take their medication every day. One in three said generic substitution made keeping track of their medications more demanding. Twenty-nine percent were anxious when they started to use a generically substituted drug. Eight percent felt that the effect of the drug had changed, and 15% reported having new or more side-effects. A negative attitude towards generics was significantly associated with low educational attainment, increasing number of drugs, having general concerns about medicine use, and having received insufficient information regarding generic substitution. Five percent of the patients had been using more than one equivalent generic drug at the same time. These were among those who used several different drugs and also among those who got their medications from more than one pharmacy. Five percent is a too small number to draw general conclusions; however, there is no reason to suspect that these mistakes do not occur from time to time.

Conclusions: This study shows that generic substitution can be an additional factor in poor drug adherence in hypertensive patients and contributes to concerns and confusion among the patients. Although generic substitution is an important measure of cost containment, health personnel should approach each patient individually. Clearly, many patients feel insecure about substituting their medication and demand more information.