This invention relates to compounds that are agonists of the muscarinic M1 receptor and/or M4 receptor and which are useful in the treatment of muscarinic M1/M4 receptor mediated diseases. Also provided are pharmaceutical compositions containing the compounds and the therapeutic uses of the compounds. Compounds include those according to formula 1a or a salt thereof, wherein n, p, Q, R1, R2, R3, R9 and R4 are as defined herein.