We selected 47 articles about online pharmacies. All of them are shown in Table 1, except 5 that had no data in addition to the number of online pharmacies found (3 articles), or did not clearly discuss the theme of selling drugs on the Internet (2 articles). The first 3 articles are by Schifano et al , who found in the Psyconaut 2002 EU Project 165 websites offering the possibility to purchase drug-related items, Schepis et al , who assessed the availability of stimulants over the Internet as a function of specific search terms used in the search engine, and Lott and Kovarik , who assessed the availability of the dermatological medications isotretinoin and terbinafine over the Internet from illicit commercial sites. We do not show in Table 1 the other 2 articles, which focus on the assessment of community pharmacy websites in Turkey and Switzerland [55,56]. The former made only a passing reference to the presence of e-commerce services, but it was not possible to determine whether they were actually selling prescription drugs; the latter also assessed the presence of e-commerce services without referring to what was actually sold online.
Contents of articles about online pharmacies, listed in alphabetical order according to first author; the presence of each item is indicated when studied and the percentage is reported when comparable; “X” indicates that the item was analyzed ...
The remaining 42 articles [10,14,27,57-95] dealing with online pharmacy characteristics are listed in Table 1, which shows the first author, year of publication, and the main features studied; due to the descriptive nature of the data it was not possible to report numerically all the results presented in the following subsections. When the numeric percentages of presence of the item were available, they are given in the table; the letter X means it was not possible to include data in the table or compare them (when, for instance, the groups they refer to are different and hence not comparable). The kind of information represented by the X is always described in detail in the text. Appendix 2 gives the sample size and the methods of selection regarding these 42 articles.
The works were published between 1999 [57,61,66] and 2011 , as shown in Figure 2, which displays the articles described in this section by year of publication and number of online pharmacies in the study sample. Less than half of the studies analyzed had more than 50 online pharmacies in their samples. Samples were obtained using a variety of methods, the most frequent being to look for online pharmacies using online search engines via various keywords. Some researchers used different sample selection methods: one found websites from received spam , while others looked for the websites indicated by other sources, such as the first one listed in the Best Online Pharmacy guide by epharmacyfinder.com , or the VIPPS list [59,76], the Pharmacychecker.com list , or the Top 100 Retailer .
Articles on online pharmacy characteristics (included in Table 1) by year of publication and number of online pharmacies in the study sample (data not reported because out of range: NABP sample of 5859 online pharmacies ).
Online pharmacy samples varied hugely in size, from 4 [83,94,95] to 5859 . The sample selection had different inclusion criteria: many studies focused on online pharmacies selling numerous kinds of drugs, while others selected online pharmacies offering a single medication or 1 class; some selected only online pharmacies not asking for a prescription, and others only online pharmacies based in specific countries. These particular inclusion criteria are shown in Multimedia Appendix 2 and are described in the subsection dealing with each issue.