[Adverse events related to substitution of generic products in Norway 2005]

The Norwegian Medicines Agency has since 2003 encouraged health professionals to report adverse events (AEs) related to generic substitution through the spontaneous reporting system. Goals of this study were to evaluate the quality of these reported AEs and to assess whether there were signals of altered efficacy or AEs related to substitution of such products.

The World Health Organisation's (WHO) tool for documentation grading was used to evaluate the AE reports. Signals of AEs were identified based on WHO's signal definition.

423 spontaneous reports concerning substitution of generic products were identified; 232 (55 %) of these reached documentation grade 1?-?3 and could be used to detect signals of AEs. The AEs were mostly common symptoms that also appear in the general population not treated with drugs. Only two of the 423 reports were classified as serious AEs. Signals of dizziness and muscle pain were identified after substitution of the original product Norvasc with the generic product Amlodipin Ratiopharm. Amlodipine was the substance associated with most AE reports; i.e. 79 (19 %) reports.

About half the spontaneous reports regarding substitution of generic products could be used for signal detection. The substitution of generics does not seem to represent a safety problem.