Treatment of hypertensive out-patients with a sustained-release dosage form of clonidine: a comparison with standard tablet therapy and long-term follow-up study.

A 12-week crossover study was carried out in 24 patients with chronic hypertension to compare the effect of clonidine given in a sustained-release form with that of a standard tablet. A long-term study (48 weeks) was performed immediately afterwards in the same patients to determine the effectiveness and acceptability of the sustained-release form in maintenance therapy. Using approximately the same dose of clonidine (300 or 450 micrograms/day for the standard tablet, 250 or 500 micrograms/day for the sustained-release form), no significant difference in hypotensive effect was found between the two forms of administration. The sustained-release form, however, was preferred by all patients because of lesser side-effects. During the long-term follow-up, the hypotensive effect was fully maintained in all patients. Side-effects which occasionally occurred at the start of the study, in particular dry mouth and a slight sensation of dizziness, subsided in the course of therapy. Laboratory investigations and clinical findings gave no indication of any chronic toxic changes.