There are no clear guidelines to provide guidance when considering switching medication for anxiety. It is reasonable to consider recommendations for depression. Factors to consider in choosing between switching vs. augmenting for depression are as follows:
According to 2016 CANMAT guidelines consider switching antidepressants when:
it is the first antidepressant
there are poorly tolerated side effects to the first antidepressant
no response to (<25% improvement to the first antidepressant
there is more time to wait for a response (less severe, less functional impairment)
If initial medication was an SSRI, and side effects are not the reason to switch, consider switching instead to an SNRI such as Venlafaxine and attempt to gradually dose to 225 mg if tolerated in order to see if patient needs noradrenergic effects seen at this dose (it is mostly a serotonergic medication at lower doses).
For Obsessive-Compulsive disorder consider switching to clomipramine if patient did not respond to adequate trials of an SSRI at higher doses and venlafaxine for at least 8 weeks each at the maximum tolerable dose.
If unable to tolerate SSRI or SNRI consider Psychotherapy or for GAD and Social Anxiety Disorder a trial of pregabalin