_Issues in measuring the proportion of counterfeit medicines_ The true scale of the counterfeit drug market remains unknown since no one has conducted a worldwide standardized effort to measure the proportion of counterfeit drugs in the global market (Newton et al 2009; WHO 2009). A counterfeit medicine is “a medicine, which is deliberately and fraudulently mislabeled with respect to identity and/or source. Counterfeiting can apply to both branded and generic products and counterfeit products may include products with the correct ingredients or with the wrong ingredients, without active ingredients, with insufficient active ingredients or with fake packaging” (WHO 2009). The share of counterfeit medicine being sold and distributed in a country indicates how well the market is regulated, generally through public rules, monitoring and enforcement but also generally including the effects of competition and suppliers‟ reputations. Both the proportion of shops selling counterfeit medicines and the average share of counterfeit medicines in any given outlet are useful measures for this aspect of government performance (Newton et al 2009).

Most studies have used convenience sampling to assess the scope of counterfeits, but for comparability and precision, initial random lot quality assurance sampling with subsequent large scale, formal random sampling is the appropriate method (Newton et al 2009). While convenience sampling is inherently biased, it can serve as an initial exploratory tool, but only a representative random sample can provide accurate assessments of the scope of the problem.

Existing studies of counterfeit medicines lack comparability for a number of reasons. One source of confusion is studies that many studies fail to distinguish between counterfeit, substandard, and expired drugs.<sup>13</sup> Other shortcomings of existing studies include the use of insufficiently large samples, announced sampling, or biased sampling. Apparently, only three peer-reviewed studies have used randomized sampling (Newton et al 2009).<sup>14</sup> For recommendations on how to objectively and systematically assess the prevalence of counterfeit medicines, see Newton et al 2009.

Until recently, the high cost of chemical analysis has inhibited large-scale analyses in developing countries. However, new technologies are sharply reducing these costs. For example, Africa Fighting Malaria recently conducted a survey of anti-malarial drugs in six major African cities to determine whether effective drugs were available. Their experience suggests that reliable representative results can be obtained in a given country for as little as US$5,000, and would rise in line with the number of medicines tested and the complexity of the sampling required to obtain a representative sample (author‟s estimate based on Bate et al 2008).

> 13 According to the International Pharmaceutical Federation (FIP – www.fip.org), substandard drugs are “genuine products which do not meet quality specifications set for them.” Expired drugs are those for which the manufacturer can no longer guarantee full potency and effectiveness.

> 14 USAID, in collaboration with the Pharmaceutical Security Institute (PSI) has compiled a list of all published studies and data on counterfeit and substandard medicines in USAID-assisted countries (USP DQI 2009). The accuracy of the data differs from study to study, yet the list itself demonstrates that counterfeit drugs are a serious problem.

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