7- and/or 8-Sulfur substituted 1,2,3,4-tetrahydroisoquinoline compounds

A compound of the formula:

• ##STR3## in which:
• R.sub.1 is mercapto, methylthio, methylsulfinyl, methylsulfonyl, trichloromethylthio, trichloromethylsulfinyl, trichloromethylsulfonyl, trifluoromethylthio, trifluoromethylsulfinyl, trifluoromethylsulfonyl or fluorosulfonyl;
• R.sub.2 is hydrogen, halo or trifluoromethyl and provided that when R.sub.1 is methylthio R.sub.2 is also methylthio, with R.sub.1 and R.sub.2 being limited to the 7 and 8 positions;
• R.sub.3 and R.sub.4 are each hydrogen or lower alkyl;
• or a pharmaceutically acceptable acid addition salt thereof.