Compounds of formula I or pharmaceutically acceptable salts thereof:
wherein R
1
, R
2
, R
3
, R
4
, n and A are as defined in the specification as well as salts and pharmaceutical compositions including the compounds are prepared. They are useful in therapy, in particular in the management of pain.
Compounds of formula I or pharmaceutically acceptable salts thereof: wherein R
1
, R
2
, R
3
, R
4
, m and n are as defined in the specification as well as salts and pharmaceutical compositions including the compounds are prepared. They are useful in therapy, in particular in the management of pain.