These psychiatric disorders are approximately 2–5 times more common in people without aura, and 3–10 times more common in people with aura. Prodrome phase
Prodromal or premonitory symptoms occur in about 60% of those with migraines, with an onset that can range from two hours to two days before the start of pain or the aura. These symptoms may include a wide variety of phenomena, including altered mood, irritability, depression or euphoria, fatigue, craving for certain food(s), stiff muscles (especially in the neck), constipation or diarrhea, and sensitivity to smells or noise. This may occur in those with either migraine with aura or migraine without aura. Neuroimaging indicates the limbic system and hypothalamus as the origin of prodromal symptoms in migraine. Aura phase
Aura is a transient focal neurological phenomenon that occurs before or during the headache. Aura appears gradually over a number of minutes (usually occurring over 5–60 minutes) and generally lasts less than 60 minutes. Symptoms can be visual, sensory or motoric in nature, and many people experience more than one. Visual effects occur most frequently: they occur in up to 99% of cases and in more than 50% of cases are not accompanied by sensory or motor effects.Visual disturbances often consist of a scintillating scotoma (an area of partial alteration in the field of vision which flickers and may interfere with a persons ability to read or drive).
Rings A, B and C are the phenanthrene ring system. This ring system has little conformational flexibility...
Two hydroxyl functional groups: a C3-phenolic [hydroxyl group] (pKa 9.9) and a C6-allylic [hydroxyl group],
An ether linkage between C4 and C5,
Unsaturation between C7 and C8,
A basic, [tertiary]-amine function at position 17, [and]
[Five]  centers  of  chirality  (C5,  C6,  C9,  C13  and  C14)  with  morphine  exhibiting  a  high  degree of stereoselectivity of analgesic action." Morphine and most of its derivatives do not exhibit optical isomerism, although some more distant relatives like the morphinan series (levorphanol, dextorphan and the racemic parent chemical racemorphan) do, and as noted above stereoselectivity in vivo is an important issue. Uses and derivatives
Most of the licit morphine produced is used to make codeine by methylation. It is also a precursor for many drugs including heroin (3,6-diacetylmorphine), hydromorphone (dihydromorphinone), and oxymorphone (14-hydroxydihydromorphinone). Most semi-synthetic opioids, both of the morphine and codeine subgroups, are created by modifying one or more of the following:
Halogenating or making other modifications at positions 1 or 2 on the morphine carbon skeleton. The methyl group that makes morphine into codeine can be removed or added back, or replaced with another functional group like ethyl and others to make codeine analogues of morphine-derived drugs and vice versa. Codeine analogues of morphine-based drugs often serve as prodrugs of the stronger drug, as in codeine and morphine, hydrocodone and hydromorphone, oxycodone and oxymorphone, nicocodeine and nicomorphine, dihydrocodeine and dihydromorphine, etc.