Buprenorphine and naltrexone effects on cocaine self-administration by rhesus monkeys.
The effects of daily treatment with buprenorphine (0.237-0.70 mg/kg/day), naltrexone (0.32-3.20 mg/kg/day) and saline on cocaine self-administration were compared in rhesus monkeys. Cocaine (0.05 or 0.10 mg/kg/injection) and food (1-g banana pellets) self-administration were maintained on a fixed-ratio 4 (variable ratio 16:S) schedule of reinforcement. Buprenorphine, naltrexone or an equal volume saline control solution were infused slowly over 1 hr through one lumen of a double lumen i.v. catheter at the same time each day. Saline and each dose of buprenorphine (0.237, 0.40 and 0.70 mg/kg/day) or naltrexone (0.32 and 3.20 mg/kg/day) were studied for 60 sessions over 15 consecutive days. Buprenorphine significantly suppressed cocaine self-administration (P less than .001-.0001) in comparison to saline in all monkeys. Cocaine self-administration decreased by 49 to 95% in five of six monkeys on the 1st day of buprenorphine administration (0.237 and 0.40 mg/kg/day) and remained suppressed by an average of 72 to 93% during buprenorphine treatment. After abrupt termination of buprenorphine treatment (0.237 and 0.70 mg/kg/day), cocaine self-administration remained suppressed for an average of 16 +/- 4.4 and 28 +/- 6.6 days, respectively. Buprenorphine (0.237 and 0.40 mg/kg/day) initially suppressed food self-administration in some monkeys (P less than .01), but tolerance developed to buprenorphine's effects on food-maintained responding whereas cocaine self-administration remained significantly suppressed. During treatment with 0.70 mg/kg/day of buprenorphine, food self-administration returned to or significantly exceeded (P less than .01) base-line levels in three animals. Daily patterns of food self-administration were not disrupted by buprenorphine treatment. Naltrexone (0.32 mg/kg/day) initially suppressed cocaine self-administration by an average of 28% over 15 days (P less than .0009). During high-dose naltrexone treatment (3.20 mg/kg/day), cocaine-maintained responding was suppressed by 25% over 15 days (P less than .01). Cocaine-maintained responding was not significantly changed by naltrexone in one of the five subjects. Food self-administration decreased by 24% (P less than .05) after 5 days of 0.32 mg/kg of naltrexone administration, then exceeded baseline levels during 3.20 mg/kg of naltrexone administration. These data suggest that buprenorphine decreases cocaine's reinforcing properties more effectively than naltrexone across the dose-range studied. Buprenorphine may be an effective pharmacotherapy for treatment of cocaine abuse as well as dual abuse of cocaine plus heroin.
Alcohol and Drug Abuse Research Center, Harvard Medical School, McLean Hospital, Belmont, Massachusetts.
N K
NK
Mello
J H
JH
Mendelson
M P
MP
Bree
S E
SE
Lukas
D000818:Animals; D002047:Buprenorphine / Q000494:pharmacology*; D003042:Cocaine / Q000008:administration & dosage*; D003216:Conditioning, Operant; D004435:Eating / Q000187:drug effects; D005260:Female; D008253:Macaca mulatta; D008297:Male; D009271:Naltrexone / Q000494:pharmacology*; D012646:Self Administration
D002047:Buprenorphine; D009271:Naltrexone; D003042:Cocaine