drrich2
Contributor
NASA has their own "cocktail" (also erroneously credited to the USCG):
"25mg each of Ephedrine and Promethazine" the first being an antihistamine and the second there to keep you awake after the first hits you.(G) Their alternative was a scop nasal spray, which was supposed to be licensed for public sale in 2012 but still pending.
Couple of observations. Ephedrine is a decongestant and bronchodilator per one source I turned up with a quick search; it's not an antihistamine, but rather a sympathomimetic. Promethazine (a.k.a. Phenergan) has some antihistaminic action; if anything I think some people find it sedating. Did you get the order in reverse accidentally?