Whether or not the anxiety disorders' response to pharmacotherapy differs between patients with and without epilepsy is yet to be established. To date, the pharmacological treatment of anxiety disorders in PWE is based on the same principles followed in the management of primary anxiety disorders and thus remains empirical. Pharmacological treatment of anxiety disorders depends on the specific type of disorder. Four classes of drugs are typically used: (i) anti-depressant drugs; (ii) benzodiazepines; (iii) AEDs; and (iv) buspirone. In the next section, we will discuss the use of these drugs in the treatment of GAD, PD, social phobia and OCD.
As shown in Table 15.2, several of the SSRIs have shown efficacy in GAD and PD; all SSRIs have also shown efficacy in OCD, but in contrast to the treatment of GAD and PD, a therapeutic effect may not be noticed for 6-12 weeks. However, a cautionary note is in order: patients with PD may be extremely sensitive to adverse events of psychotropic drugs. Accordingly, a lower initial dose should be considered and a slower titration followed than those in the treatment of mood disorders. In the case of GAD and PD, absence of desired therapeutic effect with an SSRI should be followed by a trial with the SNRI venlafaxine or duloxetine. As in the case of mood disorders, the anxiolytic effect of these drugs may not be apparent until the first 4-6 weeks after the start of therapy, for which a temporary use of a benzodiazepine is often an option.
Among the older anti-depressant drugs, the TCA imipramine is the agent of choice in PD with a comparable efficacy to that of SSRIs and has also been found to be as effective as benzodiazepines in the treatment of GAD. MAOIs are also effective in the treatment of PD.
In patients with a GAD or social phobia and a co-morbid or family risk of bipolar disorder, trials with AEDs with anxiolytic properties such as pregabalin and gabapentin should be considered first.
Their efficacy has been demonstrated in GAD and PD and anxiety secondary to life stressors or medical conditions. The risk of physical dependence and subsequent development of tolerance has limited their use to short-term trials. Typically, they are used in GAD and PD at the start of pharmacotherapy with anti-depressants until the latter agents' therapeutic effect takes over. Alprazolam is the benzodiazepine preferred for PD, while clonazepam is used in GAD.
In addition to benzodiazepines, tiagabine, gabapentin, pregabalin and valproic acid have been used by psychiatrists in the treatment of anxiety disorders [39-42]. Tiagabine and pregabalin have been found to be effective in the treatment of GAD and gabapentin in social phobia in double-blind placebo-controlled studies. In PWE who suffer from seizures of frontal lobe origin, tiagabine should be used with caution as it can cause absence stupor. Valproic acid, on the other hand, has been found to cause symptom remission in PD in a small study of 13 patients whose panic attacks failed to respond to anti-depressant agents. These findings need to be confirmed in double-blind controlled studies .
Buspirone is a 5-HTJA agonist agent that has been found to be effective for the treatment of GAD . It is favoured over the use of benzodiazepines because it does not cause drug dependence or withdrawal with long-term use and it lacks any significant pharmacokinetic interactions with other agents. Its onset of efficacy is delayed by several weeks, like that of anti-depressant drugs.
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