A test that was once commonly used involved the administration phentolamine, an a-adrenergic blocking drug. With this technique, positive response (Fig. 10.16) occurred within two to three minutes and resulted in a fall in blood pressure of at least 35/25mmHg Other pharmacological tests involved the administration of tyramir or glucagon; however, as with phentolamine, these tests yielded false positive and false-negative results.
