It is important to be aware of the limitations of country studies. For example, the nature of counterfeiting depends on the specific demand for and availability of certain categories of drugs at any given time in a country. The results of the study may therefore be influenced by the time at which sampling is undertaken.

Random sampling of selected drugs may not necessarily be the best way to find counterfeit drugs, especially if the numbers of counterfeits are few. Moreover, it may be difficult to obtain the required number of samples, or the desired number of sample units from the same batch at one outlet.

The covert purchase of samples from unauthorized outlets may pose serious problems. For example, the vendors may become suspicious of the intent if many samples of one particular batch or batches were sought and purchased. Suspicions might also be aroused if attempts are made to procure samples from more than one outlet in the same area. It is also unlikely that the national DRA could easily obtain the necessary information from the actual manufacturer of the suspected drug.