Issues in Selection of an Antidepressant

Table of Contents

1. Objectives
2. Indications
3. Antidepressant Classes
4. "Newer" Antidepressant Classes
5. Selective Serotonin Reuptake Inhibitors
6. Pharmacokinetics
7. Extra Receptor Effects
8. SSRIs in Summary
9. "New" Miscellaneous Antidepressants
10. Dual Agents
11. Special Circumstances
12. A Final Note
13. Review Questions
14. Your Feedback

Special Circumstances

Anxiety Disorders

Antidepressants are first line in patients who suffer from anxiety disorders. Moreover, over 50% of patients with Major Depressive Disorder also suffer from a co-morbid anxiety disorder at some time during the course of their illness. Many anxiety disorders are associated with over-activation of the amygdala circuits. Since serotonin is a key neurotransmitter that innervates the amygdala, serotonergic antidepressants are the ones that are generally used to treat the anxiety disorders or depressed patients with co-morbid anxiety. There are a couple of caveats that should be remembered when treating these patients:

• Patients will often feel worse before they feel better. When the drugs are first started, there is an excess of 5HT in the synapse, which can cause activation and an actual increase in anxiety and agitation. Patients need to be warned about this, and may been to be started on a low dose or given concommitent benzodiazepines
• For some disorders (e.g. OCD) a higher dosage needs to be given than for MDD
• For some disorders (e.g. panic disorder) starting dosages need to be lower than for MDD.
• Some antidepressants (e.g. bupropion) are not effective for anxiety disorders, and may actually be anxiogenic. This is because they have no effect on the serotonergic tracks.

Chronic Pain

There is an increasing recognition that many psychiatric disorders are accompanied by chronic pain, and many chronic pain states, particularly neuropathic pain, respond to psychotropic drugs. This is particularly the case with the SNRIs (serotonin norepinephrine reuptake inhibitors) as well as the tricyclic antidepressants, anticonvulsants, and alpha-2 delta ligands (pregabalin and gabapentin). These drugs are particularly helpful for the types of pain that arise in disorders such as fibromyalgia, spinal cord injury, poststroke pain, and multiple sclerosis.

Eating Disorders

Although the eating disorders require a multidisciplinary approach to treatment, there is some evidence that treatment with SSRIs can be a useful augment in treatment, particularly for bulimia and binge eating disorder. To date, fluoxetine is the only SSRI with an FDA indication for the eating disorders.