The Medical Research Involving Human Subjects Act (WMO) offers the following definition of research with a medicinal product:
‘an investigation intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of any investigational medicinal product, and/or to identify adverse reactions to any investigational medicinal product and/or to study the absorption, distribution, metabolism and excretion of any investigational medicinal product with the object of ascertaining its safety and/or efficacy; (section 1 WMO) (non-official translation)
In short: if your research has the aim of studying the mechanism of the effect, safety or effectiveness of a medicinal product, then it is research with a medicinal product. Your research must then undergo the extra, marginal review by the competent authority.
A clear definition of the term research with a medicinal product is not always easy to make. Discussion is currently ongoing on this. A handy tool is the Q&A-form part of CT Directive 2001/20/EC.
More information on whether a research with a medical device in combination with a medicine falls under the category research with a medicinal product can be found under research with a medical device.