Treatment of substance abuse

A method for treating a patient suffering from, or susceptible to, one or more symptoms of substance abuse, dependence, or withdrawal comprising administering to said patient a compound of formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• designates a single or double bond;
• n is 1 or 2;
• R1 and R2 are each independently halogen, —CN, —R, —OR, —C1-6 perfluoroalkyl, —OC1-6 perfluoroalkyl, or phenyl optionally substituted with one to five groups independently selected from halogen, —R, —OR, —C1-6 perfluoroalkyl, or —OC1-6 perfluoroalkyl;
• each R is independently hydrogen or a C1-6 alkyl group;
• R3 and R4 are taken together, with the carbon atoms to which they are bound, to form a saturated or unsaturated 4-8 membered carbocyclic ring, wherein said ring is optionally substituted with 1-3 groups independently selected from halogen, —R, or —OR;
• and
• R5 and R6 are each independently —R.