Imipramine Treatment of Panic Disorder Patients with Frequent Sleep Panic

R ecently, there is a considerable progress in understanding the neurobiology of panic disorder. An interesting phenomenon is panic attacks preceded by states of diminished arousal. Mellman and Uhde (1) suggested that there was a relationship between this phenomenon and sleep-related panic. Mellman and Uhde (2) observed that sleep panic attacks typically arose during the transition towards early delta sleep, i. e., during a state of diminishing arousal. One possible explanation for the association of sleep panic with early delta sleep may be related to carbon dioxide sensitivity in panic patients. The possibility of increased sensitivity of central medullary carbon dioxide receptors may be present in some patients with panic disorder (3). Another explanation is that reductions in respiration during deep non-rapid eye movement (non-REM) sleep lead to respiratory acidosis that triggers hyperventilation and subsequent panic (4). Sleep panic attacks are frequent in patients with panic disorder. There is an association among the severity of illness and sleep panic in panic disorder. In a previous study (5), we found that the patients with recurrent sleep panic had significantly more panic attacks per week than those without sleep panic. In addition, the patients with recurrent sleep panic had more severe panic symptoms than the others. In a recent study (6), we examined the relationship of sleep panic to major depression in patients with panic disorder and found that the sleep panickers had a higher prevalence of major depression than the other panickers. Moreover, there is an association between recurrent sleep panic attacks and suicidal behavior in patients with panic disorder (7). Thus, it may be suggested that the presence of sleep panic attacks may delineate a subgroup of panic disorder patients. In the treatment of panic disorder, imipramine is the most widely studied drug and has been effective in multiple double-blind, placebo-controlled studies (8). However, there is no evidence that it is superior (or inferior) to any other tricyclic for panic disorder and there are sometimes individual variations in sensitivity to one or another (9). An interesting topic is that imipramine has specific and significant effects in patients with sleep panic and may be useful for the reduction in the frequency of and the severity sleep panic. The purpose of this report is to demonstrate the response to imipramine treatment in panic disorder patients who reported having the experience of recurrent sleep panic attacks as primary complaint at the time of admission. Imipramine Treatment of Panic Disorder Patients with Frequent Sleep Panic