Pakistan Pharmacists Association  

Which Antidepressant Is Right for a Given Patient?

 

Question

Given the large number of antidepressants on the market, how should a clinician decide which one is best for a particular patient?

The selection of proper medications for mental health is based on several factors: the patient's biologic (medical), psychological, and social aspects are all considered before initiating therapy. As clinicians, we can use the analogy of a diamond to consider this situation. A diamond is evaluated based on its cuts (facets), clarity, color, and carat weight. Mental health patients are like diamonds with a number of facets. In psychiatry, we call this collection of facets the "Axis."

Under the DSM-IV-TR, Axis 1 is the primary mental health disorder. Axis 2 is any personality disorder or concurrent mental health condition that aggravates Axis 1 (eg, substance abuse). Axis 3 is any medical condition that the patient may be experiencing. Axis 4 consists of psychosocial stressors, and Axis 5 represents Global Assessment of Functioning.Consideration of these 5 factors is important in selecting drug therapy. For example, it is more difficult and more challenging to find a treatment for a patient with depression who also has diabetes mellitus and is a substance abuser than it is to select therapy for a patient who has the diagnosis of depression and no other concurrent disorders.

With the diagnosis, the healthcare team must investigate all reasonable medical causes for any acute change in a patient's mental health. Depression may be due to a variety of medical, psychiatric, or social reasons (legal or illicit substance-mediated). The initial assessment should include a thorough neurologic examination, as well as urine and serum toxicology if available. Basic tests should be ordered, including a complete blood cell count, serum electrolytes (especially sodium), glucose, electrocardiogram, liver and renal function tests, lipid profile, body mass index, and thyroid function. The results of these tests may identify comorbidities and/or conditions that may mimic depression and help influence the course of medication therapy.

Once depression has been confirmed and medical/psychiatric confounders identified, pharmaceutical care is defined as getting the right drug to the right patient at the right time for the right condition with a minimum of adverse effects. A mnemonic that covers the premises of pharmaceutical care is TAIDCC.

  • T: Therapeutic -- Is it the right drug?
  • A: Allergies/Accuracy -- Is the dose correct and the patient safe?
  • I: Interactions -- Are there complications with current pharmacotherapy?
  • D: Duplications of therapy -- Is the patient already receiving therapy?
  • C: Compliance/Change - Will the patient likely remain on pharmacotherapy, and how do we switch between agents?
  • C: Cost/Coverage by prescription plan -- Can the patient afford to use the medication and what are the long-term costs of the side effects?

For depression, selective serotonin reuptake inhibitors or serotonin- norepinephrine reuptake inhibitors are usually the mainstay of therapy. However, Axis 2 conditions (ie, obsessive-compulsive disorder) in a depressed patient might influence the choice of fluvoxamine over another agent.If the patient has an anxiety or substance abuse component in his or her Axis 2, perhaps an atypical antipsychotic such as quetiapine may be used.In teenagers with depression, clinicians should avoid a selective serotonin reuptake inhibitor or serotonin-norepinephrine reuptake inhibitor due to the "black box" warning related to enhanced suicidality] Treatment-resistant depression may require combinations of agents.

The main reason patients abruptly discontinue medications is side effects. Thus, an awareness of potential adverse effects that may arise from starting a new therapy must be considered. If a patient stops his or her medications, discontinuation syndrome may occur. This is a condition in which the patient experiences adverse effects resulting from an abrupt discontinuation of medication; it is linked to drug half-life, active metabolites, dose, and duration of use of the medication.

As clinicians, we should consider the patient as a whole and approach medication use from the concept of the DSM-IV-TR axis. What has the patient used before and was it successful or did it lead to reaction/ discontinuation? What has the patient's family members used before (if known and applicable) and was it successful or did it lead to reaction/ discontinuation? These 2 questions and knowledge of the axis help trim down choices of medications, and also give clues to pharmacogenomics and possible polymorphisms.

We also need to inquire about any over-the-counter agents and herbals that the patient is taking. This may identify polypharmacy and cytochrome P450 concerns and proactively prevent adverse drug outcomes such as serotonin syndrome.