Motion sickness

Scopolamine (42), an optically active, viscous Hquid, also isolated from Solanaceae, eg. Datura metell. decomposes on standing and is thus usually both used and stored as its hydrobromide salt. The salt is employed as a sedative or, less commonly, as a prophylactic for motion sickness. It also has some history of use ia conjunction with narcotics as it appears to enhance their analgesic effects. BiogeneticaHy, scopolamine is clearly an oxidation product of atropiae, or, more precisely, because it is optically active, of (—)-hyoscyamiae. 

This compound has antihistaminic activity and is usehil in the therapy of motion sickness. It may also be effective in the control of post-operative nausea and vomiting. It is classified as FDA Category B for Pregnancy, ie, no demonstrated risks shown in animal studies however, no controlled trials in pregnant women. Large doses may cause drowsiness and dry mouth owing to decreased secretion of saUva. 

Dimenhydrinate is an antiemetic especially usehil as an antinauseant in motion sickness, and for syndromes associated with vertigo such as Meniere s syndrome, radiation sickness, and vestibular dysfunction. It may produce mild drowsiness. It is FDA Category B for Pregnancy, and is available as an OTC preparation as well as by prescription. 

Mecli2ine is often used for the therapy of motion sickness and is available without prescription in a variety of formulations. 

Despite the limitations imposed by the physiology of the skin, several marketed controUed release transdermal dmg dehvery systems are available in the United States for example, scopolamine [51-34-3] for the treatment of motion sickness, nitroglycerin [55-63-0] for angina, estradiol [50-28-2] for the rehef of postmenopausal symptoms and osteoporosis, clonidine [4205-90-7] for the treatment of hypertension, fentanyl [437-38-7] as an analgesic, and nicotine [54-11-5] as an aid to smoking cessation. These systems are designed to dehver dmg for periods of one to seven days. 

The prototype of the antihistamines based on benzhydrol, diphenhydramine (3), is familiar to many today under the trade name Benadryl . Light-induced bromination of diphenylmethane affords benzhydryl bromide (2). This is then allowed to react with dimethylaminoethanol to give the desired ether. Although no mechanistic studies have been reported, it is not unlikely that I he bromine undergoes SNi solvolysis in the reaction medium the carbonitjm ion then simply picks up the alcohol. It might be noted in passing that the theophyline salt of 4 is familiar to many Iravelers as a motion sickness remedy under the trade name Oram amine . 

Impulses from the vestibular apparatus in the labyrinth are conducted via the vestibular nucleus and cerebellum to the vomiting centre. Abnormal stimulation of the vestibular apparatus is involved in motion sickness and emesis, associated with Menieres disease. 

Motion sickness arises in the vestibular apparatus. Stimulation of the semicircular canals or the utricles by unfamiliar accelerating movement may cause a mismatch between the sensory information reaching the brain centres controlling balance and posture, with that anticipated. Motion sickness may be avoided by reducing sensory conflict fixing vision on a stable reference point, such as the horizon may be effective. Cortical centres may also contribute memories of previous travel or the sight, and sounds of others being affected often increases susceptibility. 

Several histamine receptor antagonists are effective in treating motion sickness, Meniere s disease, morning sickness, uraemia and postoperative vomiting. They are not effective against cytotoxics. Antagonists with... 

These include atropine, scopolamine (hyoscine), trihexyphenidyl (benzhexol) and benzatropine. They block central muscarinic receptors involved in various afferent pathways of the vomiting reflex (Fig. 1). They have been used to control motion sickness, emesis in Meniere s disease and postoperative vomiting. Currently, hyoscine is largely restricted to the treatment of motion sickness where it has a fast onset of action but a short duration (4-6 h). Administration of hyoscine by transdermal patch produces a prolonged, low-level release of the drug with minimal side effects. To control postoperative vomiting, it should be applied >8 h before emesis is anticipated. 

It is important to note diat antivertigo dragp are essentially antiemetics because many of these preparations, whedier used for motion sickness or vertigo, also have direct or indirect antiemetic properties. They prevent the nausea and vomiting diat occur because of stimulation of die vestibular apparatus in the ear. Stimulation of diis apparatus results in vertigo, which is often followed by nausea and vomiting. 

Buclizine may be taken without water. The patient is instructed to place the tablet in the mouth and allow it to dissolve or to chew or swallow the tablet whole. When given for motion sickness, one 50-mg dose is usually effective. For more extensive travel, a second 50-mg dose may be taken alter 4 to 6 hours. When administering scopolamine, one transdermal system is applied behind the ear approximately 4 hours before the antiemetic effect is needed. About 1 gof scopolamine will be administered every 24 hours for 3 days. If the disk detaches from the body, discard it and place a fresh one behind the opposite ear. (See Fhtient and Family Teaching Checklist Applying Transdermal Scopolamine.)... 

Take die drug about 1 hour before travel for motion sickness. Buclizine may be taken witiiout water. Place die tablet in die mouth and allow it to dissolve or chew or swallow the tablet whole. 

Ms. Davis was prescribed meclizine (A ntivert-50) 50 mg for motion sickness. On return from a long car ride die tells you that the medicine did not help. Explain what questions you would ask to determine if Ms. Davis followed the prescribed drug regimen. 

Mr. Collins is prescribed transdermal scopolamine to relieve motion sickness. Discuss the rationale you would give him to stress the importance of wadiing his hands after applying or removing the transdermal system. 

D. take the drug at the first sign of motion sickness... 

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