As your inquiry is more of a medical than general discussion item, I have taken the liberty of moving it to the Diving Medicine forum in the hopes it will get some expert response.
You have many choices in medications, and all will work best as part of a comprehensive approach to sea sickness prevention.
Here's an updated version of a piece from my Jan/Feb '00 "Ask RSD" column in "Rodale's Scuba Diving" that may prove informative:
"Sea sickness, which shows wide variation in susceptibility among individuals, is not yet fully understood. It is believed to occur when portions of the brain tasked with maintaining balance receive input from the eyes, inner ear, muscles and joints that is inconsistent and unexpected over an extended period of time.
Prevention is a first step. Avoid fatigue and get adequate rest. Eat modestly, avoiding greasy, fatty, acidic and spicy foods. Don't skip breakfast, but stick to bland foods like toast, rolls and cereal. Go easy on tea and coffee, and very, very easy on alcoholic beverages. When on the boat, don't get overheated--stay under a sunshade, don't put on your protective suit until necessary, and get in the water as soon as possible. Search out a spot low and in the center where motion is minimized, face forward, focus your eyes on a fixed object on the horizon or elsewhere, avoid unnecessary neck movements and stay out of exhaust fumes. Do not go below, read anything or look through binoculars. If you must vomit, do so freely, but not anywhere on the boat, and especially not in the marine toilet.
There are plenty of medications available, and you may wish to discuss this with your physician. Among those reported to be the most effective are meclizine and scopolamine. Prescription strength meclizine commonly comes as Antivert. Scopolamine can be delivered through a transdermal patch, Transderm Scop, orally, and as a gel. The gel reportedly works faster, but not as long as the patch. Scopolamine is okayed by DAN with a trial run topside. Occasionally Phenergan is recommended. It can cause very serious drowsiness, however, and is sometimes prescribed in combination with a stimulant to counteract this. The above drugs are prescription only and have reported side effects, most commonly dryness of the mouth and drowsiness. They may also cause blurred vision, dizziness and even confusion in some users, and it is recommended to carefully discuss their use with your physician, give them a trial run prior to use in conjunction with diving, and take them only according to instructions.
Over the counter (OTC) drugs include Bonine, Dramamine (Not recommended due to demonstrated adverse effects on alertness & performance), Dramamine II (Advertised as a "less drowsy" formula. As this implies, be aware that some individuals still do experience some degree of drowsiness.) and Triptone (Same active ingredient as original Dramamine, dimenhydrinate, so draw your own conclusions) . A British drug, Stugeron (cinnarizine), has been mentioned by several sources as an effective treatment (Have seen a recent research piece suggesting impairment at higher doses), but it is not yet available in the US. Those diving in such places as Mexico & the British Virgin Islands can find it. Many report these OTC medications most effective if taken at bedtime the night prior to diving, with a second dose about an hour before diving, although recommended dosage amounts should of course not be exceeded. These medications often cause significant dryness of the mouth. Stay very well hydrated.
Considering more "natural" remedies, ginger is frequently mentioned, which can be taken in powdered, crystallized or root form (recommended preparations), or as ginger snaps, ginger ale, or tea. Just make sure they contain actual ginger and not just artificial flavoring. As heartburn with the use of ginger has been reported, also pack an antacid. Others swear by wrist straps, such as 'Sea Bands,' usually wooden or plastic balls on elastic bands which are placed so as to exert pressure on an acupressure point on the inside of the wrist. There are also 'artificial-horizon' glasses. Even aromatherapy has been tried, with a combination of mandarin, peppermint, spearmint and lavender oil being recommended.
In the final analysis, you will need to discover what works best for you with the least risk, side effect, cost and inconvenience. If you take any medications, you should understand their adverse effects and carefully follow directions for use. And remember, there is one safe, sure cure: 'Sleep under a tree all day.' "
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.
Best regards,
DocVikingo
