A liquid aerosol formulation comprising at least one thermally stable
active ingredient selected from the group consisting of butalbital,
lorazepam, ipratropium, baclofen, morphine, scopolamine, pharmaceutically
acceptable salts and esters thereof and derivatives thereof. The liquid
formulation can include an organic solvent such as propylene glycol and
one or more optional excipients. The active ingredient can be present in
an amount of 0.01 to 5 weight percent and the formulation can be heated
to provide a vapor which forms an aerosol having a mass median
aerodynamic diameter of less than 3 .mu.m.