NALTREXONE HCL TO DECREASE INCIDENCE & SEVERITY OF SELF-INJURY IN MACAQUES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: Few pharmacological interventions for self-injurious behavior (SIB) in laboratory primates have been thoroughly evaluated. As part of an ongoing long-term evaluation of naltrexone HC (compounded into a palatable syrup at 10mg/ml), behavioral data and incidence of wounding has been recorded for 17 caged subadult and adult rhesus macaques to date. In addition, the incidence and severity of wounding is being used as sole dependent variables for assessing this intervention in an additional seven subjects that rarely or never display self-biting behavior. Methods: Physical exams, complete blood counts, blood chemistry, and behavioral observation totaling 255 h were performed before beginning treatment and at regular intervals throughout the duration of the study. Animals were dosed at 3.2mg/kg orally once every 24 hours (SID). Individuals were reassessed and dosing intervals were gradually increased every two to four weeks, with a maximum interval of 96 hours. Results: Dramatic reductions in the frequency of self-biting were observed within the first week of treatment for the several subjects observed during this period. Among subjects studied behaviorally, rates of self-biting were significantly lower with both SID and EOD dosing. Bouts were less frequent, and bout length was unaffected. Naltrexone did not alter levels of other behaviors, indicating no generalized or sedating effect of the medication. Most subjects (91%) showed improvements with SID dosing, a figure that dropped to 75% with EOD dosing. Incidence of self-wounding was lower among 86% of subjects studied. Conclusions: Results suggest a possible influence of rearing background; the most dramatic improvements were seen in animals mother-reared in a social setting. Environmental as opposed to endogenous triggers may be more prevalent in nursery-reared and socially-deprived macaques. Continued research will evaluate this possibility, as well as other dosing levels and long-term efficacy.