These drugs need to be given very early in an attack to be effective; effectiveness varies amongst individuals. They are not curative drugs but can shorten attacks and reduce the intensity of an attack. Side effects are rare but can be serious. These heme-like substances theoretically inhibit ALA synthase and hence the accumulation of toxic precursors. In the United Kingdom, supplies of NormoSang are kept at two national centers; emergency supply is available from St Thomass Hospital, London. In the United States, Lundbeck manufactures and supplies Panhematin for infusion.Heme arginate (NormoSang) is used during crises but also in preventive treatment to avoid crises, one treatment every 10 days.Any sign of low blood sodium (hyponatremia) or weakness should be treated with the addition of hematin, heme arginate, or even tin mesoporphyrin, as these are signs of impending syndrome of inappropriate antidiuretic hormone (SIADH) or peripheral nervous system involvement that may be localized or severe, progressing to bulbar paresis and respiratory paralysis. Cimetidine
Cimetidine has also been reported to be effective for acute porphyric crisis and possibly effective for long-term prophylaxis. Symptom control
Pain is severe, frequently out of proportion to physical signs, and often requires the use of opiates to reduce it to tolerable levels. Pain should be treated as early as medically possible. Nausea can be severe; it may respond to phenothiazine drugs but is sometimes intractable. Hot baths and showers may lessen nausea temporarily, though caution should be used to avoid burns or falls.
Alexandrakis and Saunders found that in most cases the abducens nucleus and nerve are absent or hypoplastic, and the lateral rectus muscle is innervated by a branch of the oculomotor nerve. This view is supported by the earlier work of Hotchkiss et al. who reported on the autopsy findings of two patients with Duanes syndrome. In both cases the sixth cranial nerve nucleus and nerve was absent, and the lateral rectus muscle was innervated by the inferior division of the third or oculomotor nerve. This misdirection of nerve fibres results in opposing muscles being innervated by the same nerve. Thus, on attempted abduction, stimulation of the lateral rectus via the oculomotor nerve will be accompanied by stimulation of the opposing medial rectus via the same nerve; a muscle which works to adduct the eye. Thus, co-contraction of the muscles takes place, limiting the amount of movement achievable and also resulting in retraction of the eye into the socket. They also noticed mechanical factors and considered them secondary to loss of innervation: During corrective surgery fibrous attachments have been found connecting the horizontal recti and the orbital walls and fibrosis of the lateral rectus has been confirmed by biopsy. This fibrosis can result in the lateral rectus being tight and acting as a tether or leash. Co-contraction of the medial and lateral recti allows the globe to slip up or down under the tight lateral rectus producing the up and down shoots characteristic of the condition. Genetics
There are two known genetic associations with Duane Syndrome.