Hi Sylvester,
You might want to think of Meclizine and Dramamine as "cousins". They are both classified as antihisamines. This class of drugs "target" histamine receptors which, when stimulated by histamine released from local tissues in response to exposure to substances that initiate an allergic reaction. You get the runny nose, itching eyes, coughing sneezing etc.
Antihistamines "block" the chemical receptor sites within different tissues (found on the surface of cells). When blocked, these sites are no longer available to bind to histamine. Thus, the chemical/physical reaction to the histamine is blocked or reduced.
Almost all drugs have certain desired effects and certain "side effects."
Some side effects can sometimes severely limit the dose or usefulness of a particular drug. It turns out however, that one of the common side effects of antihistamines (in general) is to cause drowsiness, reduce or prevent nausea and motion sickness. Certain antihistamines may actually have a very strong anti-nausea/anti-motion sickness action and therefore the drug is used for it's side effect. That is why Meclizine and Dramamine (diphenhydrinate) are used for their effects other than as an antihistamine.
Many of the older antihistamines produce drowsiness. While they may well reduce or stop motion sickness, the medication many not really be appropriate for a diver. Coupled with the sedative action of nitrogen, antihistamines will have an additive effect. You might want to look at:
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=10999496
Which basically says that the drug dimenhydrinate (Dramamine) can cause serious cognitive problems. This could compromise a diver at depth and therefore should not be considered for an active diver. If you have no plans to dive on the otherhand, these medications are useful
Newer antihistamines produce less drowsiness in general but may interact with other types of medications.
Hope this helps. Be careful out there. Consult your physician for a motion sickness medication that is less likely to cause sedation/cognitive effects.
Regards,
Laurence Stein, DDS