The present invention provides muscarinic M4 receptor agonists of formula (I) and pharmaceutically acceptable salts thereof, wherein m, n, p, q, R, R2 and R3 are as defined in the specification, processes for their preparation, pharmaceutical compositions containing them and their use in the treatment of diseases such as schizophrenia, Alzheimer' s disease and various cognitive disorders as well as in the treatment or alleviation of pain.