 HIV positive patients, and patients with Hepatitis B and C, generally have a below average, and in some cases a markedly decreased, level of health owing to the nature of the respective infections and the natural course of the diseases, both of which are often complicated by an array of opportunistic illnesses. Their ill health would have been further worsened by the fact that the patients are invarious degrees of renal failure, which has its own, often debilitating, complications. If patients with HIV or Hepatitis B or C were included in the study, this could have led to statistical confusion when assessing the safety and tolerability parameters. This is because events reported by the patients, which may be a part of the spectrum of complaints in HIV positive patients and Hepatitis B and C patients, would have confounded the safety and tolerability analysis. Furthermore, Hepatitis B and C, which may cause an element of hepatic impairment, would have confounded the PK analysis due to the metabolic pathway of BIA 2-093. In addition, by administering the study medication to these subjects, any adverse events that might have occurred would have added to the discomfort of the patient. 