We assessed the potency of octreotide and midodrine, and their combination, in the treatment of the postural tachycardia syndrome (POTS) and orthostatic intolerance (OI). Nine patients with POTS and six patients with OI stood for up to 1 hour while their HR and BP were monitored. Patients received on separate days, midodrine 10 mg 1 hour before testing, octreotide 0.9 micro g/kg 8 minutes before testing or combination therapy. Standing time in the patients with POTS was 41.2 +/- 8.4 minutes and not improved by midodrine or octreotide, but increased to 56.3 +/- 2.7 (P < 0.01) minutes following combination therapy. The standing heart rate in POTS, 114 +/- 0.7 bpm, was suppressed by midodrine 92.8 +/- 0.7 (P < 0.001), octreotide 90.6 +/- 0.78 (P < 0.001), and combination therapy 84.7 +/- 0.7 (P < 0.001). Combination therapy was better than monotherapy (P < 0.001) but only for the first 10 minutes of standing. Standing time of 36.3 +/- 3.5 minutes in the patients with OI improved with midodrine, octreotide and combination therapy (55.5 +/- 3.1, 56.5 +/- 3.5, and 56.6 +/- 3.3, respectively, P < 0.05 for each). Standing heart rate in OI was 100 +/- .76 bpm; following midodrine it was 80.3 +/- .69 (P < 0.05), following octreotide it was 84.8 +/- .86, and following combination therapy it was 71.2 +/- .9 (P < 0.01). The RR interval versus time area under the curve (The Orthostatic Index) was 21.1 +/- 4 in patients with OI. After midodrine it was 41.4 +/- 3.5 (P < 0.01), after octreotide 40.3 +/- 3.8 (P < 0.01) and after the combination it was 47.3 +/- 4.6 (P < 0.001). Midodrine and octreotide suppressed tachycardia in POTS and improved standing times in OI. The two drugs had similar potencies; combination therapy was not significantly better than monotherapy.

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The purpose of this study was to determine whether autonomic neuropathy and the postural tachycardia syndrome can be treated with octreotide LAR (Long Acting Release). This was an open-label pilot project. Protocol 1 Patients with autonomic neuropathy (n = 4) were given increasing doses of octreotide LAR once a month for three months. Blood pressure was measured in the sitting posture every two weeks. Pretreatment mean blood pressure averaged 83.8 +/- 7.1 mm Hg. After four, six and eight weeks of therapy the blood pressures averaged 96.3 +/- 6.4, 98.2 +/- 6.1 (p < .025), and 104.1 +/- 3.1 (p < .025) respectively. Therapy led to a dramatic improvement in symptoms in one patient but another had an unacceptable elevation in supine blood pressure. Protocol 2 Patients with POTS or orthostatic intolerance were given 10, 20, or 30 mg of octreotide LAR over three months. Seven patients entered and five completed the study. After two months treatment, standing time increased from 36.0 +/- 9.2 to 59.2 +/- .8 minutes (p < .01). Heart rate in the standing position was suppressed from 106 +/- .83 to 93.2 +/- .8 beats per minute (p < .05). Orthostatic dizziness and chronic fatigue improved. We conclude that octreotide LAR can be used to treat autonomic neuropathy but there is a risk of an excessive pressor response. Octreotide LAR improved standing time and suppressed tachycardia in patients with orthostatic intolerance.