was discovered accidentally when developing the new antitubercular drug isoniazid. The drug was found to cause euphoria and improve the patient's appetite and sleep quality. The first Tricyclic antidepressant, Imipramineis, was developed by modifying the structure of antihistamine (Promethazine). TCAs can increase the level of norepinephrine and serotonin by inhibiting their reuptake transport proteins. The majority of TCAs exert greater effect on norepinephrine, which leads to side effects like drowsiness and memory loss. In order to be more effective on serotonin agonism and avoid anticholinergic and antihistaminergic side effects, selective serotonin reuptake inhibitors (SSRI) to treat anxiety disorder. First SSRI, fluoxetine, was reported in 1974 and approved by FDA in 1987. After that, few more SSRI like sertraline, paroxetine, escitalopram have entered the market. The first serotonin norepinephrine reuptake inhibitor (SNRI), venlafaxine, entered the market in 1993. SNRIs can target serotonin and norepinephrine transporters while imposing insignificant effect on other adrenergic (α1, α2, and β), histamine (H1), muscarinic, dopamine, or postsynaptic serotonin receptors. Classifications There are six groups of anti-anxiety medications available that have been proven to be clinically significant in treatment of anxiety disorders. The groups of medications are as follows. Antidepressants Medications that are indicated for both anxiety disorders and depression. Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are new generations of antidepressants. They have a much lower adverse effect profile than older antidepressants like monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressant (TCAs). Therefore, SSRIs and SNRIs are now the first-line agent in treating long term anxiety disorders, given their applications and significance in all 6 types of disorders. Benzodiazepines Benzodiazepines are used for acute anxiety and could be added along with current use of SSRIs to stabilize a treatment. Long-term use in treatment plans is not recommended. Different kinds of benzodiazepine will vary in its pharmacological profile, including its strength of effect and time taken for metabolism. The choice of the benzodiazepine will depend on the corresponding profiles. Benzodiazepines are used for emergent or short-term management. They are not recommended as the first-line anti-anxiety drugs, but they can be used in combination with SSRIs/SNRIs during the initial treatment stage. Indications include panic disorder, sleep disorders, seizures, acute behavioral disturbance, muscle spasm and premedication and sedation for procedures. Buspirone Useful in GAD but not effective in treating phobias or social anxiety disorders. Antiepileptics Useful in treating GAD Antipsychotics Olanzapine and risperidone are atypical antipsychotics which