Dimenhydrinate is available as a 50-mg/mL solution for injection in 1- and 10-mL multiple-dose vials.3962 Each mL contains dimenhydrinate 50 mg in propylene glycol 50% and water for injection with benzyl alcohol 5% as a preservative.3962 Sodium hydroxide and/or hydrochloric acid may have been added to adjust the pH.3962 Dimenhydrinate contains 53 to 55.5% of diphenhydramine and 44 to 47% of 8-chlorotheophylline.3962
pH
From 6.4 to 7.2.3963
Dimenhydrinate may be administered by intramuscular injection undiluted or by intravenous injection over 2 minutes only after dilution with 10 mL of sodium chloride 0.9%.3962
Dimenhydrinate injection should be stored at controlled room temperature and protected from light.3962
pH Effects
A test of dimenhydrinate solutions at pH 2 to 10 showed no separation or precipitation at pH 5.4 to 8.6 on extended room temperature storage. Below pH 5.4, a white powdery precipitate of 8-chlorotheophylline formed within 24 hours. Above pH 8.6, an oily liquid separated within 30 minutes.279
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