By Joanna Lyford, Senior medwireNews Reporter
Simply changing the appearance of a prescription medication can significantly alter patients' compliance with treatment, study findings show.
Accordingly the study authors call for a reevaluation of current regulations that allow bioequivalent drugs to vary in appearance.
At present, generic drugs must be comparable to brand-name versions with regard to dosage form, strength, route of administration, quality, intended use, and clinical efficacy. However, they can vary widely with regard to color, shape, size, texture, aroma, and flavor.
"A patient taking five medicines, each produced by five generic manufacturers, theoretically faces over 3000 possible arrays of pill appearances for what are, chemically and clinically speaking, the same drugs," write Aaron Kesselheim (Brigham and Women's Hospital, Boston, Massachusetts, USA) and colleagues in the Archives of Internal Medicine.
To investigate the potential impact of this variability on compliance, Kesselheim's team used the Health-Core Integrated Research Database to identify all patients who filled a first prescription for one of seven antiepileptic drugs after January 2002.
Patients were categorized as cases (n=11,472) if they had incomplete persistence to their medication, defined as failure to fill a new prescription within 5 days of the elapsed days supplies, or as controls (n=50,050) if they had no gap in treatment. Cases and controls were matched for demographic and clinical variables.
The drugs taken by participants came in 37 different colors and four different shapes, report Kesselheim et al. The two refills preceding nonpersistence were considered to be "concordant" if the pill color and/or shape matched or "discordant" if they did not.
Analysis showed that while discordance in pill appearance was rare, it was more common preceding cases of drug nonpersistence. Specifically, color discordance was seen in 136 cases (1.20%) but only 480 controls (0.97%), giving an adjusted odds ratio (OR) of 1.27. Similarly, shape discordance was seen in 18 cases (0.16%) and 54 controls (0.11%), giving an OR of 1.47.
The association with color discordance was also present in the subset of patients diagnosed with seizure disorder, with an adjusted OR of 1.53.
The researchers claim that this is the first empirical analysis to link the appearance of a pill to patients' medication adherence and to demonstrate that patients who experience changes in pill color have an increased risk for interrupting their medication use.
"Promoting medication adherence is a difficult task, and it has been only partially addressed through strategies such as enhanced prescribing of generic drugs and reducing drug copayments," they write.
"Taking steps to permit (or even require) similarity in pill appearance among bioequivalent brand-name and generic drugs may offer another way to achieve better patient adherence to essential medication regimens."
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