Pholedrine is the N-methyl derivative of hydroxyamphetamine and has been suggested as an alternative drug in localising the causative lesion in OSP.
A study comparing pupil responses to phenylephrine 1% and hydroxyamphetamine 1% in 14 consecutive patients with OSP after previously confirming the diagnosis with cocaine 10%21 found that phenylephrine 1% increased pupil size in postganglionic OSP by a mean of 2.
Given the limited availability of hydroxyamphetamine and the similarities in sensitivity and specificity of the two drugs in localising a lesion to the postganglionic neuron, phenylephrine 1% appears to be the more reliable and readily available alternative.
For more than 30 years, cocaine 2-10% has been the gold standard in the diagnosis of unilateral Horner's syndrome and hydroxyamphetamine 1% recommended to localise the causative lesion.
Hydroxyamphetamine test for diagnosis of postganglionic defects.
False-negative hydroxyamphetamine (Paredrine) test in acute Horner's syndrome.