With aerosolized administration of medicines, direct access to the lung is possible. Depending on the intrapulmonary behavior of each molecule, the aerosol mode of administration makes possible either a pulmonary topical action or a systemic action, thanks to the lung's wide vascular network. An inhaled molecule's pulmonary behavior is not predictable and must be studied on its own. Some medicines with a systemic aim have a topical effect after aerosol administration: furosemide, amiloride, morphine, interferons, cyclosporin and prostacyclin. Other medicines have systemic effects after aerosol administration: insulin, growth hormone, LHRH, calcitonin and nicotine. Heparin can be classified in either group depending on the dose and type of use.