Changes in blood pressure, heart rate, and sympathetic activity on abrupt withdrawal of tiamenidine (HOE 440) in essential hypertension.

A limitation of clonidine therapy is the syndrome of rebound hypertension and sympathetic overactivity after withdrawal. Ten patients, four male, six female, aged 28--64 years, with essential hypertension, were treated for one year with an imidazoline derivative, tiamenidine. Blood pressure fell from an average of 178/108 mm Hg pretreatment to 152/86 mm Hg after 1 year. Tiamenidine was then withdrawn in hospital, replaced by identical placebo under single blind conditions and observations made over 96 h. The study was interrupted in five patients (4 patients within 36 h) because blood pressure rose to greater than 30 mm Hg (systolic) or greater than 20 mm Hg (diastolic) above pretreatment values. For the group, blood pressure was maximal at 194/112 mm Hg, 18 h post withdrawal, significantly higher than pretreatment (p less than 0.005). Headache, tremor, flushing and insomnia were noted. Saliva production rose 100% at 24 h. Plasma noradrenaline rose within 24 h with an accompanying rise in urinary metanephrine and catecholamine excretion. Tiamenidine appears to share with other imidazolines rebound cardiovascular and autonomic effects following abrupt withdrawal.