Panic disorder tricyclic antidepressants

Long-term efficacy and tolerability is of considerable clinical importance for any medication proposed for the treatment of panic disorder. Tricyclic antidepressants, in particular, are associated with side effects such a weight gain and anticholinergic effects, which may make them difficult for patients to tolerate long-term. 

Antidepressants are as effective as benzodiazepines in the treatment of panic disorder. Moreover, antidepressants do not have the same risks of tolerance and dependency that are associated with benzodiazepine treatment. However, antidepressants take longer to work, so that significant improvement might not be observed until after a month of treatment. Although tricyclic antidepressants have been approved for the treatment of panic disorder, the effectiveness of selective serotonin reuptake inhibitors (SSRIs) in its treatment has led them to become the favored treatment among antidepressant drugs. 

Beyond these issues, it should be noted that antidepressant medications also are used in the treatment of anxiety disorders. Tricyclic antidepressants and SSRIs both have been used in the treatment of such anxiety disorders as panic disorder, obsessive-compulsive disorder, and posttraumatic stress disorder. 

Tricyclic Antidepressants (TCAs). The TCAs, particularly imipramine (Tofranil), were also discovered soon after their introduction to be effective in the treatment of panic attacks. Imipramine, the best-studied TCA in the treatment of panic disorder, is most often helpful at daily doses of 150-250 mg, though it must be started at 10-25 mg, usually at bedtime, and gradually increased over 2-4 weeks. Although they are not as well studied, many clinicians prefer to use the secondary amine TCAs, desipramine (Norpramin) and nortriptyline (Pamelor), because they have milder side effects than imipramine. Clomipramine (Anafranil), though probably the TCA with the greatest side effect burden, is often said to be most effective in patients with refractory disease. 

Tricyclic Antidepressants (TCAs). Because of their effectiveness not only for depression but for anxiety disorders such as panic disorder as well, TCAs were the first medications formally tested in the treatment of PTSD. Three TCAs, amitriptyline, imipramine, and desipramine, have been studied in small trials, producing modest benefit for reexperiencing and hyperarousal symptoms, without any relief of avoidance/numbing symptoms. Given this limited benefit in conjunction with the side effect burden and potential for toxicity in a suicide prone population, TCAs are infrequently used in the treatment of PTSD. Please refer to Chapter 3 for more information regarding TCAs. 

A considerable number of tricyclic antidepressants have been developed in the past, although with slight differences in their pharmacological activities, ah with similar efficacy. They are primarily indicated for the treatment of endogenous depression. However this does not exclude efficacy in patients in whom the depression is associated with organic disease or in patients with reactive depression or depression combined with anxiety. They may also benefit patients during the depressive phase of manic-depressive disorder. For some also efficacy has been claimed in panic states, phobic disorders, and in obsessive-compulsive disorders. 

SRls are currently the most prevalent pharmacological treatment used for panic disorder [see Westenberg and Den Boer, Chapter 24, in this volume], even though tricyclic antidepressants, monoamine oxidase inhibitors [MAOls], and benzodiazepines are also effective. The efficacy of the SRI antidepressants and the observation that initially they may induce deterioration of symptoms [which is usually not the case with treatment of depressed patients with the same medications] raise issues related to the pathobiology of anxiety and its comorbidity with depression. 

Benzodiazepines (BZDs) have been used for the treatment of depression because their sedative effects can reduce insomnia, agitation, and anxiety symptoms that frequently accompany depressed states. Considerable evidence also indicates that major depression may accompany panic and agoraphobic disorders ( 199, 200 and 201). When depression precedes the onset of panic disorder, clinical experience suggests a better response to antidepressants than to BZDs, although no studies have directly addressed this issue (202). Conversely, available evidence indicates that when depression occurs after the onset of panic disorder, treatment with either a BZD or a tricyclic may result in concomitant improvement of both the panic and depressive symptoms (198, 199, 200, 201,202 and 203). Depression, however, has been reported to be an adverse effect of BZD treatment. 

TABLE 13-5. Tricyclic antidepressant versus placebo treatment of panic disorder... 

Noyes R, Garvey MJ, Cook BL, et al. Problems with tricyclic antidepressant use in patients with panic disorder or agoraphobia results of a naturalistic follow-up study. J Clin Psychiatry 1989 50 163-169. 

Beta-adrenoceptor antagonists, particularly propranolol, have been shown to be effective for anxiety symptoms particularly in situational anxiety and GAD. Buspirone, an azaspirodecanedione, is an agonist at 5-HTlA receptors and seems to have anxiolytic effects, though it is less potent than the BDZs and the effects take up to three weeks to become evident. There is high first pass metabolism and a considerable proportion of the effect is due to a metabolite (1-PP). The principal adverse effects of buspirone are nausea, gastrointestinal upset and headache. Antidepressant drugs, both the older tricyclic antidepressants and the newer drugs, have been demonstrated to have anxiolytic effects in mixed anxiety-depressive patients, GAD and panic disorder. 

The selective serotonin reuptake inhibitors (SSRIs) represent a chemically diverse class of agents that have as their primary action the inhibition of the serotonin transporter (SERT) (Figure 30-3). Fluoxetine was introduced in the United States in 1988 and quickly became one of the most commonly prescribed medications in medical practice. The development of fluoxetine emerged out of the search for chemicals that had high affinity for monoamine receptors but lacked the affinity for histamine, acetylcholine, and adrenoceptors that is seen with the tricyclic antidepressants (TCAs). There are currently six available SSRIs, and they are the most common antidepressants in clinical use. In addition to their use in major depression, SSRIs have indications in GAD, PTSD, OCD, panic disorder, PMDD, and bulimia. Fluoxetine, sertraline, and citalopram exist as isomers and are formulated in the racemic forms, whereas paroxetine and fluvoxamine are not optically active. Escitalopram is the S enantiomer of citalopram. As with all antidepressants,... 

By the 1970s and early 1980s it was recognized that certain tricyclic antidepressants and monoamine oxidase (MAO) inhibitors were effective in treating panic disorder and one tricyclic antidepressant (clomipramine) was effective in treating obsessive-compulsive disorder. Thus, there began to be recognized that some antidepressants overlapped with anxiolytics for the treatment of anxiety disorder sub-types or for mixtures of anxiety and depression (Fig. 8—8). However, either anxiolytics... 

Tricyclic antidepressants. Imipramine and clomipramine have been the most extensively studied of the tricyclic antidepressants and both have demonstrated efficacy in treating panic disorder. Other tricyclic antidepressants that have shown some evidence of efficacy include desipramine, doxepin, amitriptyline, and nortriptyline. 

FIGURE 9-6. Various treatments can be given in combination for panic disorder (i.e., panic combos). The basis of all many combination treatments is a serotonin selective reuptake inhibitor (SSRI). Other antidepressants such as venlafaxine, nefazodone, mirtazapine, tricyclic antidepressants, and monoamine oxidase inhibitors can all have antipanic actions, although they are second-line treatments, as are the benzodiazepines. On the other hand, benzodiazepines are often added to SSRIs, particularly at the initiation of an SSRI and intermittently when there is breakthrough panic. Cognitive and behavioral psychotherapies can also be added to any of these drug treatments. 

Obsessive-compulsive disorder may be linked to abnormalities of the neurotransmitters serotonin and dopamine. The neuroanatomical basis of OCD may be related to dysfunction in the basal ganglia. The hallmark of treatment for OCD is use of SSRIs plus the tricyclic antidepressant clomipramine. Panic disorder is characterized by unexpected panic attacks, possibly linked to abnormalities in the neurotransmitters norepinephrine and GABA, in the sensitivity of benzodiazepine receptors, or even in the regulation of respiration. Drag treatments include SSRIs, several of the newer antidepressants, high-potency benzodiazepines, many tricyclic antidepressants, and MAO inhibitors. 

The tricyclic antidepressant desipramine is effective in panic disorder and obsessive compulsive disorder. 

In addition to the treatment of depression, the Food and Drug Administration (FDA) has approved the (on-label) use of the antidepressants for treatment of panic disorders, obsessive-compulsive disorders, bulimia nervosa, social phobia, and generalized anxiety disorder. And although not the treatment of choice, the tricyclics are sometimes used for enuresis—bed wetting. 

The tricyclic antidepressants are effective in treating severe major depression. Some panic disorders also respond to TCAs. Imipr-amine has been used to control bed-wetting in children (older than 6 years) by causing contraction of the internal sphincter of the bladder. At present it is used cautiously, because of the inducement of cardiac arrhythmias and other serious cardiovascular problems. 

Therapeutic uses The primary indication for fluoxetine is depression, where it is as effective as the tricyclic antidepressants. Fluoxetine is effective in treating bulimia nervosa and obsessive-compulsive disorder. The drug has been used for a variety of other indications, including anorexia nervosa, panic disorder, pain associated with diabetic neuropathy, and for premenstrual syndrome. 

Antidepressant drugs of various classes (tricyclics, monoamine oxidase inhibitors, SSRIs) have broad efficacy in generalized anxiety and in panic disorder, for which they are the treatments of choice (6,7). While not likely to cause benzodiazepine-like dependence or abuse, they do have a significant therapeutic latency, and the older drugs are very toxic in overdose. 

Switch to tricyclic antidepressant for panic disorder if continued medication is required. 

The mood and anxiety disorders in their various permutations constitute a major source of personal suffering and impaired ability to engage in productive Avork and interpersonal relationships. Between 5 and 9% of women and between 2 and 3% of men meet the diagnostic criteria for major depression at any time 10-25% of all women suffer major depression sometime in their lives, while 5-10% of men will develop major depressive disorder (American Psychiatric Association, 1994). The anxiety disorders obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), panic disorder, and generalized anxiety disorder (GAD) show lifetime prevalence rates of approximately 2.5%, 7%, 2.5%, and 5% respectively. Between 3 and 13% of individuals in community samples are regarded to meet the diagnostic criteria for social phobia. Mood and anxiety disorders are common comorbidities (American Psychiatric Association, 1994) and the most common antidepressant medications including the serotonin reuptake inhibitors, the mixed serotonin-catecholamine reuptake inhibitors, the tricyclic antidepressants, and the monoamine oxidase inhibitors, are all effective treatments for anxiety and panic attacks. 

Imipramine (brand name Tofranil) Often referred to as the grandfather of all antidepressants. It is the oldest tricyclic antidepressant available and has traditionally been used for the treatment of depression and for those who have panic attacks. It is sometimes used now to assist with withdrawal from cocaine addiction and in obsessive-compulsive disorder. 

Four patients taking tricyclic antidepressants (imipramine, clomipramine, dibenzepin) and one taking viloxazine relapsed into depression when they took co-trimoxazole (trimethoprim with sulfamethoxazole) for 2 to 9 days. The reasons are not known. Another patient treated for 5 years with alprazolam and imipramine for panic disorder and who had not had panic attacks for several months developed insomnia, anxiety and panic attacks within 6 days of starting to take co-trimoxazole. The panic... 

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