Interim report on clinic intake and safety data collected from 17 NIDA-funded naltrexone studies

In 17 studies of naltrexone, a totoal of 1,536 patients had been logged in as potential study subjects as of February 29, 1976. Of these, 883 had been started on study medication, including 107 on placebo as controls. A relatively high rate of attrition was seen in all studies over the first two months of study medication; this attrition rate tended to flatten out at about the fourth month. Of the 883 subjects beginning study medication, 47 (5.3%) were subsequently terminated for medical reasons. The data available on 45 of these subjects indicate equivalent percentages, both with respect to the total number of dropouts in the two study medication groups (naltrexone: 39 of 676, or 5.0%; placebo: 6 of 107, or 5.6%) and to the number of dropouts which the clinic reported as "possibly drug-related" (naltrexone: 6 out of 676, or 0.9%; placebo: 1 of 107, or 0.9%). However, one of the "possibly drug-related" dropouts developed idiopathic thrombocytopenic purpura after the administration of naltrexone for approximately 13 months during four separate treatment admissions. Statistical review of the data and subsequent analyses of the five double-blind, placebo-controlled studies administered by the National Academy of Sciences revealed no significant medication-group differences with respect to the physical/psychiatric or laboratory data. A review of the symptom data and analyses indicates that the frequency of occurrences of certain of the gastrointestinal tract symptoms recorded was somewhat higher in those subjects treated with naltrexone. Specific symptoms involved included "Loss of Appetite", "Abdominal Pain or Cramps", "Nausea or Vomiting", and "Constipation". However, the relative severity of these symptoms for all subjects experiencing any symptomatology was not statistically differentiable with respect to study medication group.