There is really no sure fire way to choose an antidepressant specific for are Parkinson's patients. Most Dr's work off past experience as to what may work best for a particular patient. The problem that may exist sometimes is that the depression can be organic (already within the person's mind) or brought on by PD.
I usually see Dr's trying the newer antidepressants first due to the less incidence of side effects and that smaller doses are showing to be more effective than larger doses of older medications.
As far as choices of antidepressants used in people with Parkinson's that have depression and anxiety are usually:
(1) SSRI's (Selective Serotonin Reuptake Inhibitors):
(2) SNRI's (Serotonin Norepinephrine Reuptake Inhibitors):
Effexor & Effexor ER (Vanlafaxine & Vanlafaxine ER)
(3) Atypical (Because their Mechanism of action does not fir into any other group)
Wellbutrin & Wellbutrin SR (Buproprion & Buproprion SR)
This is usually the order in which they are tried in most patients and also based on the Dr's previous experience with the medications. All of these antidepressants work on both depression and anxiety. Their are certain circumstances where the anxiety is too much to be controlled by a certain antidepressant. At this point it will be at the Dr's discretion as to choose to add a Benzodiazipine, such as Ativan (Lorazepam), Klonipin (Clonazepam), Librium (Chlordiazepoxide), Valium (Diazepam), or Xanax (Alprazolam). Depending on the situation the Dr may add an antianxiety medication with the antidepressant or decide to withdraw the antidepressant and solely use the antianxiety medication.
I many patients I will use a scenario of relieving headache pain. To make it simple, I will say that there are basically 3 options: Tylenol (Acetaminophen), Motrin or Advil (Ibuprofen), and Bayer (Aspirin). People who have Liver issues will want to stay away from Tylenol (Acetaminophen) due to the fact it is broken down by the liver. If a person has stomach issues such as ulcers or sensitive stomachs, they will want to sty away from Motrin or Advil (Ibuprofen) because it is very tough on the stomach. Lastly, if a person has an issue with blood thinners or sensitive stomachs, they will want to stay away from Aspirin.
As yo can see many issues are involved in choosing just a pain medication, the choice of an antidepressant that helps with anxiety could choose to be an even tougher decision.
I hope this help and please keep me posted.