PRELIMINARY-OBSERVATIONS ON THE USE OF MIDODRINE IN TREATING ORTHOSTATIC HYPOTENSION IN FAMILIAL DYSAUTONOMIA

Midodrine, a peripheral alpha-adrenergic agonist, was evaluated in 7 f emale and 2 male patients with familial dysautonomia (FD), a disorder characterized by decreased sympathetic innervation. Prior to and after three months of midodrine treatment, each patient's response to postu ral change was assessed by arteriosonde readings of blood pressure and heart rate, corrected QT-interval measurements, Doppler evaluation of renal blood flow and circulating atrial natriuretic peptide (ANP) lev els. The initial midodrine dose (2.5 mg three times daily) was raised until subjective symptoms improved. Doses were reduced if patients fel t jittery or developed erect hypertension (systolic > 180 mmHg or dias tolic > 110 mmHg). Midodrine, at an average dose of 0.25 mg/kg per day , improved subjective symptoms in all patients. With treatment, magnit ude of blood pressure responses was variable. Although mean erect bloo d pressure did not increase significantly for the aggregate, it did in crease in six of nine patients. In addition, the QTc interval normaliz ed and erect renal perfusion improved. Changes in supine mean blood pr essure and supine circulating AMP correlated directly. We judge midodr ine to be useful in management of orthostatic hypotension in patients with familial dysautonomia.