Effects of repeated doses of pseudoephedrine on blood pressure and plasma catecholamines in normal subjects and in patients with phaeochromocytoma.

1. Increases in blood pressure (BP) and in plasma noradrenaline concentration (NA) were observed after two doses of a non-prescription decongestant containing pseudoephedrine (PE) in two of three patients with phaeochromocytoma, before but not after removal of the tumour. The pressor response was terminated by oral phenoxybenzamine, and modified by prior exposure to this drug. 2. In eight normal subjects administration of the same two doses prevented falls in BP and in NA usually seen with prolonged recumbency, but neither BP nor NA increased. However, a pressor response was observed in a normal subject with a strong family history of hypertension. 3. Exposure to PE in non-prescription decongestants is not without risk in hypertension.