Norpholedrine

para-Hydroxyamphetamine (PHA), also known as Norpholedrine (Oxamphetamine, Paredrine), 4-hydroxyamphetamine (4-HA), and α-methyltyramine (α-Me-TRA), is a sympathomimetic drug, that is, a drug that stimulates the sympathetic nervous system. When used in eye drops, it dilates the pupil. Norpholedrine is sold in combination with tropicamide under the brand name Paremyd. It occurs as a metabolite of amphetamine.

Once thought to be a human invention, norpholedrine is now known to occur as an alkaloid in plants including Acacia berlandieri.

Night vision
In 1944, the US Naval Submarine Medical Research Laboratory researched the use of Paredrine to improve adaptation to night vision in submarine personnel. A significant improvement in adaptation was shown in the 17 subjects they tested.