These descriptive names can be misleading, however, as many were assigned historically, solely on the basis of subjective clinical examination, which is not sufficient to determine the eyes true trajectory. Optokinetic (syn. opticokinetic) nystagmus: a nystagmus induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or stripes. For example, if one fixates on a stripe of a rotating drum with alternating black and white, the gaze retreats to fixate on a new stripe as the drum moves. This is first a rotation with the same angular velocity, then returns in a saccade in the opposite direction. The process proceeds indefinitely. This is optokinetic nystagmus, and is a source for understanding the fixation reflex. Postrotatory nystagmus: if one spins in a chair continuously and stops suddenly, the fast phase of nystagmus is in the opposite direction of rotation, known as the "post-rotatory nystagmus", while slow phase is in the direction of rotation. Treatment
Congenital nystagmus has long been viewed as untreatable, but medications have been discovered in recent years that show promise in some patients. In 1980, researchers discovered that a drug called baclofen could stop periodic alternating nystagmus. Subsequently, gabapentin, an anticonvulsant, led to improvement in about half the patients who took it. Other drugs found to be effective against nystagmus in some patients include memantine, levetiracetam, 3,4-diaminopyridine (available in the US to eligible patients with downbeat nystagmus at no cost under an expanded access program), 4-aminopyridine, and acetazolamide.
The main limiting side-effects of alpha antagonists is that the baroreceptor reflex is disrupted and thus this can cause postural hypotension. Phenoxybenzamine also has irreversible antagonist/weak partial agonist properties at the serotonin 5-HT2A receptor. Due to its 5-HT2A receptor antagonism, phenoxybenzamine is useful in the treatment of carcinoid tumor, a neoplasm that secretes large amounts of serotonin and causes diarrhea, bronchoconstriction, and flushing. Stereoisomerism
Phenoxybenzamine contains a stereocenter, so there are two enantiomers, the (R)- and the (S)-forms. All commercial preparations contain the drug as racemate. See also
Ketanserin
Pindobind
Phentolamine

References
External links
 Media related to Phenoxybenzamine at Wikimedia Commons