Ativan (lorazepam) is an effective medicine for occasional or short-term anxiety. Head-to-head comparisons of medication uses, side effects, ratings, and more. It comes as a tablet, capsule, liquid, and quick dissolving tablet. Benadryl (Diphenhydramine) makes you more tired than Claritin, Allegra, Oral solution. Nov 13, - The peak effects are usually seen in the first few hours of using. The full It is also available in some other forms like orally disintegrating tablet. Benzodiazepine, Onset of Action2, Peak Onset (hrs), Half-life parent (hrs). Half-life metabolite (hrs). Comparative Oral Dose. Long Acting. Chlordiazepoxide Missing: disintegrating ?allegra.