An oral clonidine dosage unit providing a twenty-four hour extended release profile following a single dose administration is provided. The dosage unit comprises a pharmaceutically effective amount of a coated complex comprising clonidine bound to a cationic exchange resin, which is characterized by a twenty-four hour release profile with a single peak, wherein said oral clonidine dosage unit provides a therapeutically effective plasma concentration for at least about 70%, or at least 85% of the twenty-four hour period following the single dose administration. Both liquid and solid formulations are provided, as are methods of treating a patient by a single administration of a formulation of the invention so as to achieve a therapeutic effect for 24-hours.