The present invention relates to a liquid pharmaceutical composition suitable for administration by inhalation which comprises a diluent and a suspension of particles of 9,10-dimethoxy-2-(2,4,6-trimethylphenylimino)-3-(N-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one (RPL554) or a pharmaceutically acceptable salt thereof. Also described is a liquid pharmaceutical composition according to the invention for use in the treatment of the human or animal body.
