There seems to be a problem in many patients who switch from Alprazolam/Xanax to Lorazepam/Ativan.Lorazepam 1 mgm is considered equal to 0.5 mgm Alzalopram.
Though there is a similar anxiolytic effect,some patients find that there is a antidepressant like effect with the alprazolam which is missing with the lorazepam.Further the halflife of lorazepam is 10-20hours whereas the alprazolam has a half life of 6-12 hours and is a more speedy/ with a high.
The addiction potential of alprazolam is much more than that of lorazepam,it would take some time to adjust to the switch.There is more tiredness while taking the lorazepam.There appears to be a strong psychological dependence on alprazolam which often gives symptoms of withdrawal even though bioequivalent doses of other benzodiazepines may be given.
Benzodiazepines are not proper drugs for lomg term use due to their strong dependence/addiction potential and should ideally not be used formore than 2-4 weeks when treating anxiety .Further,0.5 mgm of alprazolam is a bioequivalent of 10 mgm of diazepam.Hence ,the 3 mgm of xanax you were taking is equivalent of 60 mgm of Diazepam which is quite a high dose.
Further,the effect of almost all benzodiazepines tends to wear off in a couple of hours on long term use.With repeated daily dosing,there is accumalation of the drug in the blood ands also in the fatty tissue of the body leading to fairly high levels.Ideally complete withdrawal from benzodiazepines using a very gradual tapering dose over a long time would be best done under the supervision of a psychiatrist as these drugs are addictive in nature.