Pregabalin 's anxiolytic effect appears after one week of use and is similar in effectiveness to lorazepam , alprazolam , and venlafaxine , but has demonstrated more consistent therapeutic effects for psychic and somatic anxiety symptoms. Long-term trials have shown continued effectiveness without the development of tolerance , and unlike benzodiazepines, it does not disrupt sleep architecture and produces less severe cognitive and psychomotor impairment. Pregabalin also exhibits a lower potential for abuse and dependence than benzodiazepines.  
Parenteral: 25 mg IV or IM, followed by close observation for response. This dose may be repeated within 2 hours if needed. Oral therapy should be started as soon as feasible if continued medication is required.
Oral: 25 mg at bedtime. Alternatively, mg may be administered before the evening meal and again at bedtime for antihistamine effects.
Rectal: 25 mg at bedtime. Alternatively, mg may be administered before the evening meal and again at bedtime for antihistamine effects.
The safety of Phenergan for long-term treatment of allergic rhinitis has not been established.