A set of membranes called the vestibular membrane and the basilar membrane develop to separate the cochlear duct from the vestibular duct and the tympanic duct, respectively.Parts of the otic vesicle in turn form the vestibulocochlear nerve. These form bipolar neurons which supply sensation to parts of the inner ear (namely the sensory parts of the semicircular canals, macular of the utricle and saccule, and organ of Corti). The nerve begins to form around the 28th day. Molecular regulationMost of the genes responsible for the regulation of inner ear formation and its morphogenesis are members of the homeobox gene family such as Pax, Msx and Otx homeobox genes. The development of inner ear structures such as the cochlea is regulated by Dlx5/Dlx6, Otx1/Otx2 and Pax2, which in turn are controlled by the master gene Shh. Shh is secreted by the notochord. Middle ear
The middle ear and its components develop from the first and second pharyngeal arches. The tympanic cavity and auditory tube develop from the first part of the pharyngeal pouch between the first two arches in an area which will also go on to develop the pharynx. This develops as a structure called the tubotympanic recess. The ossicles (malleus, incus and stapes) normally appear during the first half of fetal development. The first two (malleus and incus) derive from the first pharyngeal arch and the stapes derives from the second. All three ossicles develop from the neural crest.
Cevimeline (trade name Evoxac) is a synthetic analog of the natural alkaloid muscarine with a particular agonistic effect on M1 and M3 receptors. It is used in the treatment of dry mouth and Sjögrens syndrome. Medical uses
Cevimeline is used in the treatment of xerostomia (dry mouth), and Sjögrens syndrome. It increases the production of saliva. Side effects
Known side effects include nausea, vomiting, diarrhea, excessive sweating, rash, headache, runny nose, cough, drowsiness, hot flashes, blurred vision, and difficulty sleeping.Contraindications include asthma and angle closure glaucoma. Mechanism of action
Cevimeline is a cholinergic agonist. It has a particular effect on M1 and M3 receptors. By activating the M3 receptors of the parasympathetic nervous system, cevimeline stimulates secretion by the salivary glands, thereby alleviating dry mouth. See also
Pilocarpine — a similar parasympathomimetic medication for dry mouth (xerostomia)
Bethanechol — a similar muscarinic parasympathomimetic with longer-lasting effect

References
External links
Evoxac (cevimeline HCl hydrate capsules) Full Prescribing Information