Recent Developments in the Treatment of Panic Disorder (PD) and Generalized Anxiety Disorder (GAD)

Abstract

There is a high prevalence of panic disorder (PD) in the community. The National Comorbidity Survey, a US study of over 8000 adults in the general population, found a lifetime prevalence rate of 3.5%. This is a higher prevalence than that reported in earlier epidemiological studies, which documented lifetime prevalence rates of between 1.2 and 2.4%. Panic disorder is typically a disorder of young adults, with an impact on quality of life, in terms of social, personal, and economic consequences, at least comparable to that of major depression. Benzodiazepines, as well as selective serotonine reuptake inhibitors (SSRIs) have been studied thoroughly in acute and long-term PD. However, there is a lack of data to answer the question if there is an enhanced efficacy with the combination of psychological treatments as well as to guide the clinicians what to do after non-response.

Generalized anxiety disorder (GAD) is a chronic illness with an estimated one year prevalence of approximately 3%, and a lifetime prevalence of approximately 6%. GAD (without depression comorbidity) is associated with significant impairment in quality of life and functioning which has been found to be comparable to major depressive disorder, and chronic medical illnesses such as diabetes and arthritis. At least 5 classes of drugs are available for the pharmacologic management of GAD (Bandelow et al., 2008), each acting via different mechanisms: (1) benzodiazepines (diazepam, lorazepam, alprazolam, etc) which augment inhibitory GABAergic activity; (2) monoaminergic reuptake inhibitors, consisting of SSRI drugs with serotonin selectivity (paroxetine, escitalopram, sertraline), SNRI drugs with dual serotonin/ norepinephrine activity (venlafaxine-XR, duloxetine), as well as some first generation tricyclics (imipramine); (3) azapirones (buspirone) which modulate monoaminergic transmission; and (4) pregabalin, which acts presynaptically to inhibit excitatory neurotransmission. Two other classes of medication (antihistamines such as hydroxyzine; antipsychotics such as quetiapine) and recently a herbal remedy, silexan, have also demonstrated efficacy in the treatment of GAD. Cross-study comparisons suggest that each class of drug has a different benefit-risk profile. However, relatively few double-blind, placebo-controlled head-to-head trials have been published which provide direct comparisons of the efficacy and safety profiles of drugs in each class.