Letter commenting on a paper by JJ Lopez-Picazo et al. (Atencion Primaria May 2011;43(5):254-262).  They note that the study only takes into account interactions between prescribed drugs recorded electronically, and so does not include for example old prescriptions still being renewed, self medication, or interactions with food, alcohol, grapefruit juice or herbal medicines (such as hypericum).  They also do not consider that use of the e-PIG index gives an accurate estimate of the risk of drug interactions for a particular patient, as (1) the e-PIG index incorrectly classifies drugs which are rarely used but have numerous potential interactions as being of low risk, and (2) it does not take characteristics of individual patients into account.

There is a response on behalf of the original authors.