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Anxiety: Pharmacotherapy

Medications are the most common treatment for anxiety disorders. However, they can be costly and they all have side-effects.

Medications with evidence to support their use in anxiety fall into three groups:

  • antidepressants
  • anxiolytics 
  • other psychotropic agents used mainly to augment antidepressants


All of the antidepressants have been shown to be variously effective in reducing symptoms of the anxiety disorders. (see Table 4.2: First- and second-line antidepressant medications, indications, doses and cautions)

  • SSRIs and SNRIs are effective in treating panic disorder, social anxiety disorder, obsessive-compulsive disorder, posttraumatic stress disorder and generalized anxiety disorder.
  • There is evidence for the efficacy of NaSSAs.
  • TCAs and MAOI/RIMAs are effective but are generally less well-tolerated than SSRI or SNRIs and are reserved for later choice.


All antidepressants should be started at a very low dose in anxiety disorders. Anxious patients can be extremely intolerant of the side-effects of agitation and akathisia that may occur at the onset of treatment. Doses of fluoxetine and escitalopram as low as 5 mg daily are often necessary.

Use the lowest dose available of SNRIs (e.g., venlafaxine 37.5 mg daily). Despite starting at a low dose, the ultimate effective dose is usually the same as in major depression or even higher.

Anxiety disorders often need prolonged treatment before the desired results are achieved. It is better to start at a low dose with a gradual increase over a long period of time than it is to challenge patients with doses that they cannot tolerate, leading to frequent switching of medications.

Lack of treatment response

If the first SSRI or SNRI does not help at all after eight weeks, discontinue it slowly and use another SSRI or SNRI. If two medications do not work, a specialist referral may be advisable. In obsessive-compulsive disorder (OCD), consider a switch to clomipramine with the usual precautions for tricyclics (e.g., cardiac arrhythmias, seizure risk, suicide risk). If there is a partial benefit, consider adding another agent.


The overall duration of medication treatment in anxiety disorders is one year or more followed by slow tapering. Many patients relapse during the withdrawal phase. The rate of relapse is reduced when treatment includes cognitive-behavioural therapy (CBT), or when CBT is introduced during tapering.


Benzodiazepines are effective for most anxiety disorders. They do not offer much benefit in OCD. Care needs to be taken in posttraumatic stress disorder due to very high rates of comorbid substance use disorders. It is advisable to avoid benzodiazepines in acute stress disorder.

Dependence is a significant problem. Inter-dose exacerbation of anxiety can be confused with worsening of the original disorder. For benzodiazepines, make a contract with the patient about the discontinuation date. Six to eight weeks of use in a new case is the suggested limit while an antidepressant is co-administered and then continued as the benzodiazepines are tapered.

Buspirone can be helpful in generalized anxiety disorder and to augment antidepressant treatment. It does not have the acute therapeutic effects of benzodiazepines.

Augmenting agents

Many agents can be used to enhance the effects of antidepressants in the anxiety disorders. Atypical antipsychotics add to the improvement with antidepressant treatment. With OCD, there is well-established evidence for adding haloperidol or risperidone in a low dosage (0.5 mg daily or twice a day) to an SSRI or SNRI. The combination is particularly effective for tics.

In comorbid cases where the anxiety disorder occurs with a second disorder, augmenting the anti-anxiety treatment with a drug for the second disorder can be very useful (e.g., SSRI/SNRI plus anticonvulsant in anxiety disorder with bipolar disorder, SSRI/SNRI plus stimulant for comorbid attention-deficit/hyperactivity disorder).

Atypical antipsychotics have been extensively studied as monotherapy in anxiety disorders, but they are not approved for this indication in Canada.

Related Portico Network topics

Understanding psychiatric medications (patient handouts):

  • Antidepressants
  • Antipsychotics
  • Mood stabilizers
  • Benzodiazapines


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