Abstract: Two sustained-release dosage forms, enteric-coated granules and tablets compressed from enteric-coated granules, were prepared for a long-acting effect of the prodrug clorprenaline pamoate.Using the dissolution rate in vitro and the antiasthmatic activity in vivo as indexes, a comparison was made between the sustained-release effects of the two dosage forms. The tablet made from enteric-coated granules was shown to be an ideal sustained-release dosage form. The tablet was shown through clinical tests, as expected, to have insignificant side-effects and to prolong the antiasthmatic activity to about 12 hours.